Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: frpax on June 21, 2016, 04:55:39 pm
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Hello all!
I joined this forum, because there seems to be a wealth of knowledge here, and I definitely need help!
One of my neighbors threw away an old 1957 Hammond M3-A1 organ, so I (being the resourceful guy that I am) grabbed the AO-29 amp and the field coil speaker, as well as quite a bit of the organ's nice looking wood so I can make a cool cabinet for the amp. Recycling at its best!
I did get some help from a guy named Brad (aka the Guitologist on YouTube and Facebook, who is a great guy, btw) as he took a slightly later version of the AO-29 and converted it to guitar, but his did not have the field coil speaker. But, I managed to copy his schematic as best as I could, with the only real difference being the field coil stuff.
Now. Here's my problem. I'm not schooled enough to take a schematic and turn it into an actual physical layout. I can read the schematic OK...I know what all the symbols mean and stuff, but physically going from schematic to real item, I can't do. So this is where I need some help from you gurus.
Now I CAN read a layout or wiring diagram really well, something like this:
(http://sluckeyamps.com/6v6plexi/P-6V6_07.jpg)
That's super easy for me to visualize and build.
So what I need is my schematic:
(http://img.photobucket.com/albums/v376/fpaxton/AO-2920Schematic_zpsndwecjwd.jpg)
to be turned into a layout like above.
I would really like to utilize as much of the original Hammond parts as possible, to keep costs down and mojo factor up!
I plan on using the Hammond chassis and transfomers, tubes, sockets, and as many of the caps and resistors as possible.
Oh, forget the tremolo circuit. I decided I'd probably never use it. Instead, I want a tone stack that is Bass, Mids, & Treble, like Sluckey's Plexi 6V6.
Can anyone help me with this?
Any and all comments or suggestions are greatly appreciated!
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Could you post some pictures of your actual gear you want to use?
Sluckey is an expert in these Hammond conversions.
I had some difficulty starting out, trying to reuse various chassis' and their previous layouts.
If you have problems working out your own layouts,
it might be best to use Doug's chassis and circuit board on your build.
You'll obviously use as many parts from the Hammond as you can,
and you will probably have a better chance of success using Doug's proven layout and board. :icon_biggrin:
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Could you post some pictures of your actual gear you want to use?
Sluckey is an expert in these Hammond conversions.
I had some difficulty starting out, trying to reuse various chassis' and their previous layouts.
If you have problems working out your own layouts,
it might be best to use Doug's chassis and circuit board on your build.
You'll obviously use as many parts from the Hammond as you can,
and you will probably have a better chance of success using Doug's proven layout and board. :icon_biggrin:
Not a problem:
(http://img.photobucket.com/albums/v376/fpaxton/A70DF2B2-469D-4F09-96DA-24552EEF6DBE_zpszwzocktz.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/06DFEF76-CC8B-4FA6-B0C9-7E329748B4A0_zpsihibytpl.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/5771BDFD-6C81-4397-9C22-8EE6199F7A74_zpscqcmmpqf.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/47894EFB-3202-42E6-9629-B98298BDD0A5_zpsos20ufqd.jpg)
The big transformer is stamped AO-22111-1
The smaller one has AO-20936-3 on the top metal part and AO-20935-4 on the brown waxy paper stuff on the inside
My tube layout from L-R is:
V-11: 5U4
V-10: not using (6BA6 - I was going to use this as a tremolo circuit borrowed from a Silvertone 1482 schematic and use a 6AU6 in place of the 6BA6)
V-6: 6V6
V-5: 6V6
V-3: 12AU7
V-4: 12AX7
V-2: 6AU6 - but I can modify that to a 12AX7 easily enough
V-1,8,7,9: not using
Anything else you need?
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I wasn't familiar with that specific model's layout.
It seems to be laid out similar to our guitar amps.
Many other organ amps aren't.
There are certain challenges in reusing the chassis,
but on this model they don't appear to be overwhelming.
The toughest part for you will likely be developing a layout,
that can re-use the parts board already in there. :icon_biggrin:
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The toughest part for you will likely be developing a layout,
that can re-use the parts board already in there. :icon_biggrin:
That's EXACTLY what I need, a layout!
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OK, but the layout depends on the parts placement.
With the 6V6 Plexi I made I have 6 pots on the front, and the NFB presence pot on the back.
Do you have the front 6 pot locations planned on this chassis?
They need to be kept away from noisy areas, like the PS and OT.
Then you want to use your board as efficiently as possible.
Keeping your leads short and away from problem areas.
Depending on the pots placements, this may require a significant departure from the traditional layout plan.
Or you could try to just copy the parts board layout and make your leads whatever length they need to be.
I really try hard to keep my leads as short as possible and away from problem areas.
But I have significant experience in Point to Point wiring, and now some experience in modifying a board's layout.
It takes lots of planning to get this right.
Practice following the schematic through the boards layout, you'll figure that out after a while.
Then if a layout change is necessary, you will have an idea about what needs to move and where it should go.
You will learn a great deal figuring this out on your own. :icon_biggrin:
Unless Sluckey already has a layout plan for this, I doubt anyone will want to develop a custom layout for you. Sorry.
It is a lot of work to develop a trouble free layout plan. :icon_biggrin:
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Thanks Paul.
I figured doing a layout was a lot of work.
Sluckey mentioned using Visio for his planning. It would be beyond my wildest dreams if Visio converted a schematic to a layout!
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If no custom layout plan is available,
Using Doug's chassis and board is still a good option. :worthy1:
I suspect you could get those and a few misc parts needed to build the 6V6 Plexi for around $100.
If you got the organ amp for free, and can make a Plexi out of it for anything less than $200, you are doing good. IMO
Take a look at the BOM on Doug's plans.
If you were to buy all the parts from him for this amp,
it would cost around $450 not including shipping. :icon_biggrin:
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If no custom layout plan is available,
Using Doug's chassis and board is still a good option. :worthy1:
I suspect you could get those and a few misc parts needed to build the 6V6 Plexi for around $100.
If you got the organ amp for free, and can make a Plexi out of it for anything less than $200, you are doing good. IMO
Take a look at the BOM on Doug's plans.
If you were to buy all the parts from him for this amp,
it would cost around $450 not including shipping. :icon_biggrin:
Where can I find Doug's plans?
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http://el34world.com/schematics.htm#Plexi_6V6_build (http://el34world.com/schematics.htm#Plexi_6V6_build)
:w2:
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OK, so help me out here for a sec, please.
I'm working very hard to visualize the schematic to the real thing.
So I follow the power cord into the the PT (T7) and then out to the rectifier tube/6V6 heaters/etc., which is on the lower portion of the schematic. Then the circuit has to connect to the part of the schematic that is at the top somehow.
Does the "+290" at the bottom connect to the "+290" at the top by the OT (in RED)?
And the "310" at the bottom is the "310" at the top (in GREEN)?
And I assume that everything in the ORANGE bubble should stay exactly intact?
(http://img.photobucket.com/albums/v376/fpaxton/94BBA305-AA49-437B-B8B7-F30DD13807F9_zpslnumhaoh.jpg)
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The schematic shows you have a field core speaker as part of your PS.
This is not part of the normal 6V6 Plexi PS.
If you have the FC speaker and it works well,
you could probably modify the Plexi PS to keep it.
I modified my 6V6 Plexi PS and used +325VDC for my B+,
This PS is even less than that.
Doug's plan has over 400V for B+ I think.
If you want to get all the power you can out of the 2 6V6s,
then they normally jack up the voltage well above 400V.
I like to run my vintage tubes a little more conservatively. :icon_biggrin:
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Yes, I do have the field coil speaker and I assume it works... I had to repair a few tears with some hot glue.
As for my vintage 6V6's, I'm not looking to get the most out of them. Just looking for good tone that isn't TOO hard on them.
At this point, I am thinking that I'll keep this schematic and just run with what I've got.
By looking at my schematic with the bubbles and lines on it, am I thinking right, that the ones indicated connect together?
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Yes your Red and Green blocks are your voltage supplies.
That circuit looks like it should sound pretty good as a guitar amp.
It might be easiest to get that circuit up and then see if you really want to mess with it. :icon_biggrin:
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I have used organ chassis for guitar amps, and found myself figuring what needed to be done first... to the power supply, in order for it to function how I need it to. Then I remove the board, and clear the parts off of it. You then can figure out values of the old parts individually, and use only the ones that test out in the specs you need. Audio path passive circuits can use some of the old Carbon Comps...but the rest you are better off using metal film resistors, and NEW Electrolytic caps.
The board you have there is huge, and has enough space to build nearly anything.
You can choose from hundreds of layouts to build whatever style amp you want...it starts with part placement related to the tubes, input and control pots. You have plenty of good places to ground things in there as well.
Just do some research on parts choices for your build, ideal locations... to keep unwanted interactions from occurring, (wiring and circuit related) and translate a layout to your board.
It really is not that difficult. If you do not understand electronics enough...on this one, find a tech friend to help lay out your amp, and learn as you go.
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Yes your Red and Green blocks are your voltage supplies.
That circuit looks like it should sound pretty good as a guitar amp.
It might be easiest to get that circuit up and then see if you really want to mess with it. :icon_biggrin:
That's my intention. Run with what I've got, and if I hate it, then I'll start really changing it.
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I originally wanted to place my pots on the same side that the OT is, that is, the opposite side of the tube sockets.
But if they should not be near any transformers, do I need to place them on the same side as the tube sockets?
That would really clutter up that side of the chassis, so is it absolutely necessary?
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Nice response guitardude57 :worthy1:
You are absolutely correct that it really is not that difficult.
It can be learned, and practice makes perfect.
Honestly though, it takes a lot of dedicated work and that takes a lot of time.
I don't mind that, it keeps me busy and learning.
I think others without previous electronic experience may find the whole process rather overwhelming without some SME guidance like you just gave.
SME = Army jargon for Subject Matter Expert :laugh:
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I originally wanted to place my pots on the same side that the OT is, that is, the opposite side of the tube sockets.
But if they should not be near any transformers, do I need to place them on the same side as the tube sockets?
That would really clutter up that side of the chassis, so is it absolutely necessary?
These are the challenges of re-using the organ chassis.
I had spent much time just staring at my junk organ amps,
trying to figure out what I needed to do to make it a guitar amp.
HBP finally got me over my mental block of the organ amp parts being locked into their current positions.
You need to visualize the parts you have as a clean slate.
Find a proven layout for the guitar amp you want to build.
Then try to visualize how you can place the parts you have like they are on the amp you want to build.
Figure out if that is feasible using the same organ chassis.
It will likely require drilling new holes for parts and maybe covering the old holes.
Lots of work that you will need to figure out mostly on your own.
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What are the dimensions of your AO-29 chassis?
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What are the dimensions of your AO-29 chassis?
21.5 x 5 inches
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What's the third dimension?
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What's the third dimension?
Duh.. Depth is 2.5"
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Those dimensions seem adequate to fit the Plexi circuit in to me. :dontknow:
I think Sluckey and Doug have both built the 6V6 Plexi in a chassis smaller than that.
It's working out all those little challenges of part placement, and making the holes etc. for them to fit.
I'm interested in seeing your progress with whatever path you choose. :icon_biggrin:
I built my 6V6 Plexi in a Hammond Organ H100 Series Amplifier AO-70-1 chassis.
It was the build that finally got me over my parts placement visualization roadblock.
I've got less than $100 in junk parts into mine.
But realistically, well over $1000 in man hours to get it built.
It certainly won't win any build beauty contests.
But it sounds fantastic, and doesn't have any hum or noise issues.
Later, I'll try to post a picture of my ugly duckling Plexi for you to check it out. :icon_biggrin:
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I would suggest this layout (or very similar) for that AO-29 chassis. My turret board will not work in this chassis because my board is too wide and your tube layout calls for a board that's kinda a mirror image of my board. Same situation with Hoffman's board. So you gotta roll your own board. Everything should fit on the suggested board size.
I do not recommend using that 380-0-380vac PT from that AO-29. Your B+ will be way too high.
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sluckey has visualized and documented an excellent example of a parts placement that will fit your organ chassis. :worthy1:
He has located the parts so that you can keep your leads short and away from problem areas.
I expect that if you used his suggested parts placements, you would have a successful, problem free build.
Unfortunately, you still need to be able to translate the schematic to your circuit board layout.
This is where many of those untold man hours begin to accumulate.
It might be frustrating for you to do that at first.
But if you stuck to it and worked through the process you would learn a great deal.
If you feel that rolling your own circuit board is beyond your abilities at this time,
that pretty much forces you to go with Doug's chassis and proven circuit board.
That is, if you really want to make a 6V6 Plexi out of what you have. :icon_biggrin:
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I would suggest this layout (or very similar) for that AO-29 chassis. My turret board will not work in this chassis because my board is too wide and your tube layout calls for a board that's kinda a mirror image of my board. Same situation with Hoffman's board. So you gotta roll your own board. Everything should fit on the suggested board size.
I do not recommend using that 380-0-380vac PT from that AO-29. Your B+ will be way too high.
Sluckey, you're da MAN!
This is what I have been envisioning, and you have the components in nearly the identical places that I've been thinking about.
As for a PT, what do you suggest I replace it with?
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sluckey has visualized and documented an excellent example of a parts placement that will fit your organ chassis. :worthy1:
He has located the parts so that you can keep your leads short and away from problem areas.
I expect that if you used his suggested parts placements, you would have a successful, problem free build.
Unfortunately, you still need to be able to translate the schematic to your circuit board layout.
This is where many of those untold man hours begin to accumulate.
It might be frustrating for you to do that at first.
But if you stuck to it and worked through the process you would learn a great deal.
If you feel that rolling your own circuit board is beyond your abilities at this time,
that pretty much forces you to go with Doug's chassis and proven circuit board.
That is, if you really want to make a 6V6 Plexi out of what you have. :icon_biggrin:
Ive been watching some YouTube videos about making a custom board. I'm sure that I can do it.
If I'm going to do this much modification, I can probably use the layout from several Plexi 6V6's that I've seen.
This is going to be fun!
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Here is a pic of my junk parts Plexi.
Built exclusively with old parts I had on hand.
It might not look that great, but she definitely Rocks.
This was my 1st real chassis reconfiguration and circuit board customization.
I learned a lot from it, and have gotten better at this whole process with each successive build. :icon_biggrin:
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Based on the basic layout that Sluckey did, I've decided to shitcan my Hammond AO-29 schematic and go with a more straightforward Plexi 6V6 plan.
Suggestions are very welcome!!
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Go with Doug's Plexi 6V6. He sells every part you need, including punched chassis. He makes it easy. You don't even have to put together a parts list or do any of the dirty work. Just put it together following his layout.
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Go with Doug's Plexi 6V6. He sells every part you need, including punched chassis. He makes it easy. You don't even have to put together a parts list or do any of the dirty work. Just put it together following his layout.
OK!
So I went with Sluckeys basic layout for my chassis and board. Then I converted Doug's turret board to fit my boards size.
I went from this:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_0993_zpswd5bmkdv.jpg)
to this, that fits my chassis:
(http://img.photobucket.com/albums/v376/fpaxton/961FAB36-1EEB-495E-A9F3-86FE0BFE72BA_zpsxtqzdlsl.jpg)
I think it will work!
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I found a small error between the layout of Doug's turret board and his actual board.
Take a look at the yellow circled areas.
Layout:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_0993%20edit_zpso7xudw5p.jpg)
And actual turret board:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_0994edit_zpshhez1lk9.jpg)
Which one is correct? Or does it even matter?
Here is his complete layout versus his completed actual board.
Layout:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_0996%20edit_zpsii1idakb.jpg)
Actual board:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_0997%20edit_zps8yvyeipe.jpg)
Help, please? I'm going to order the board from Doug and I need to know which one or if it makes no difference!
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I've been busy today!!
I've designed the cabinet for this chassis.
This is a little rough, but it should look a lot like this:
(http://img.photobucket.com/albums/v376/fpaxton/6348D6F3-8918-4170-8862-EF63F74C8B17_zpsx030y4a1.jpg)
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Help, please? I'm going to order the board from Doug and I need to know which one or if it makes no difference!
Modify message
They are both electrically the same and will both work just fine. I suspect the actual board you get will look like the one in the pdf document layout, not the one in the photo of the prototype amp Doug first built.
Send Doug a pm if you need more info.
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It can be a lot of work to re-purpose an organ chassis.
But I'm getting better at it each time I do it. :icon_biggrin:
Here's my not quite finished adaptation of Doug's 6V6 Plexi.
The addition of 2 more 6V6's worked out very well.
She's a killer amp, that just needs some final tweaks and her paint job completed. :icon_biggrin:
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Since I need a choke for the Plexi 6V6, would a Fender BF Deluxe Reverb choke made by Mercury Magnetics work?
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As long as the choke is rated for the mA of current you will pull through it you can use it.
The Henries rating deals with it's filtering capabilities.
Since the choke usually comes after the main B+ which is drawing the majority of the current,
there is usually no need to use an expensive, over current capable choke.
If you already have a beefier choke than necessary you could use it, I did on my Quad Plexi, but why buy a new one like that?
Most little chokes will work fine for a simple PP 6V6 circuit. :icon_biggrin:
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As long as the choke is rated for the mA of current you will pull through it you can use it.
The Henries rating deals with it's filtering capabilities.
Since the choke usually comes after the main B+ which is drawing the majority of the current,
there is usually no need to use an expensive, over current capable choke.
If you already have a beefier choke than necessary you could use it, I did on my Quad Plexi, but why buy a new one like that?
Most little chokes will work fine for a simple PP 6V6 circuit. :icon_biggrin:
I happen to have a brand new MM Fender BFDR choke on hand and it is rather small in size.
I also happen to have a brand new MM Vox AC-15 choke and it is MUCH larger. About the size of an average Output Transformer.
The Fender one will easily fit my chassis real estate. The Vox, not so much...
Also, I have a new MM Fender Tweed Deluxe OT. Would that work better for my Plexi 6V6 instead of my Hammond one?
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I am very unfamiliar with all those new parts.
I buy cheap, junk tube gear off Ebay.
Figure out, to the best of my ability, what my junk parts are capable of, and try to put them to good use. :icon_biggrin:
My Quad 6V6 has used parts that I paid less than $150 for.
It is not easy to do it this way, but if you are cheap like me it can work. :l2:
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I happen to have a brand new MM Fender BFDR choke on hand and it is rather small in size.
I also happen to have a brand new MM Vox AC-15 choke and it is MUCH larger.
Use the Fender choke. It's fine. The Vox choke is much larger because all current for the entire amp must flow through it.
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Use the Fender choke. It's fine. The Vox choke is much larger because all current for the entire amp must flow through it.
Thank you! I was looking at the MM website, and these little chokes are $48!!
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I've been busy this week!
If you recall, the amp design is going to look something like this (I modified it a teeny bit):
(http://img.photobucket.com/albums/v376/fpaxton/42CD5C37-F4F8-47D8-B474-10880E191794_zpsccfw09he.jpg)
So, here's the almost done front panel, rescued from the original organ (need to cut out the portion where the chassis will be):
(http://img.photobucket.com/albums/v376/fpaxton/C05C4D5E-E89D-405A-80D4-D01763D85F30_zpsrifq8kpw.jpg)
And since the chassis had lots of holes in it and I needed it to look pretty, so I cut out some pieces of sheet metal from other unused parts of the amp and JB Welded them into place and then sanded it real smooth. The marks you see on the front of the chassis is where I'll be drilling holes for pots and switches, etc.:
Chassis front (upside down):
(http://img.photobucket.com/albums/v376/fpaxton/3E51503C-806A-4B4E-A74C-74F8C2BC6041_zps2urzurey.jpg)
Disregard the messy work bench and dig the 1983 boom box which still works, by the way, but only as a radio. Blasts out Classic Rock only!
Back:
(http://img.photobucket.com/albums/v376/fpaxton/83D3148F-0889-4B2A-8045-9AA676545D19_zpsbumgaro2.jpg)
Altogether, I'm very happy with how the project is coming along. I'm re-purposing many of the original organ stuff and also re-purposing a lot of other stuff I have collecting dust in my garage.
I'm selling off a bunch of power and output transformers (Mercury Magnetics and a couple Allen transformers on eBay in order to fund what I don't have to complete this. My user name is 6stringer if anyone is interested. I don't have them all listed yet, but will by tomorrow.
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Wow! You are doing a really fine job!
Much better than me. :l2:
Looks like you have much better tools than I do.
Using nice new clean parts has a certain appeal to it.
But cleaning up some nasty junk that would have most likely ended up in a landfill and reusing the parts, is better IMO.
Then making a kick ass guitar amp from it is something to be quite proud of.
Doing that at 1/4 or less of the new parts costs, helps to keep the wife off my case. :l2:
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Wow! You are doing a really fine job!
Much better than me. :l2:
Looks like you have much better tools than I do.
Using nice new clean parts has a certain appeal to it.
But cleaning up some nasty junk that would have most likely ended up in a landfill and reusing the parts, is better IMO.
Then making a kick ass guitar amp from it is something to be quite proud of.
Doing that at 1/4 or less of the new parts costs, helps to keep the wife off my case. :l2:
Thanks, Paul!
I don't have any really special tools, per se. I used a Dremel to cut the fill in pieces on the chassis. Then an orbital sander to sand it smooth. I used a circular saw on the front panel and will use a jigsaw to cut the part out for access to the controls. I REALLY wish I had a table saw for that... would have saved me a ton of time. I do have a router, that I'll be using to round off all the corners of the cabinet.
Just a lot more time involved by having minimal power tools. And I'm really taking my time. Measuring twice and cutting once, that sort of thing. It's more a job of paying attention to details.
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While waiting for some money to come in so I can work on my amp, I still have been busy working on the cabinet.
Here are a few quick pics:
(http://img.photobucket.com/albums/v376/fpaxton/962203C9-A9DD-45D1-BFDA-B3E64BD780A9_zpstra62bhu.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/BAF5A8A5-379B-4C1C-9C54-34850C428938_zpsqycyyqvp.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/9CC0C845-BD4F-4B29-8585-F16A1F658BCA_zpsa7btnszj.jpg)
All the wood except the bottom are from the original organ!
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I made the back slats out of that thing on the organ that folds up to hold the sheet music:
(http://img.photobucket.com/albums/v376/fpaxton/FFBB1032-976E-4E80-8DF6-5B6ED5251EDC_zpsuir8vavn.jpg)
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A few more, this time with the empty chassis installed and the tweed corner on the front:
(http://img.photobucket.com/albums/v376/fpaxton/760E21DE-110F-41F4-B7D3-C3A2EC1F8C12_zps7cjip5lc.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/57536322-DE79-4525-B49C-0C292900C708_zpsivzxfbcs.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/D0CCD4F5-8C03-443B-929A-E174ED1300BB_zpsnm4xmowl.jpg)
Still have to round the squared corners with a router.
Also, I'm going to buy some either black or gold piping to go around the front speaker panel and that tweeded corner.
I think it's looking fairly decent. It would be nicer (meaning more square) if I had a table saw. But you do what you can do, right?
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It's looking outstanding to me! :worthy1:
Don't be too hard on yourself, and sing:
"I know, it's only Rock-n-Roll, but I Like it"!
"I Like it, Like it, Yes I do"! :l2:
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It's looking outstanding to me! :worthy1:
Don't be too hard on yourself, and sing:
"I know, it's only Rock-n-Roll, but I Like it"!
"I Like it, Like it, Yes I do"! :l2:
Thank you!
I had to change a few things from both my original AND revised designs. Some things look great on paper (literally!), but don't work out so well unless you have the proper tools. Oh well, I'm still pretty pleased with how it is looking!
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Of course I kept the serial # plate from the original organ, and I mounted it on the bottom back slat.
(http://img.photobucket.com/albums/v376/fpaxton/83B0F0FF-5AFA-43FC-B638-417FB44D0ED3_zpsajfokqlv.jpg)
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I'm close to ordering my turret board material an turrets... do I need one of those staking tools to install the turrets? (I do not want to make my own)
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yes
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yes
Thank you, sluckey!
Also, the Hoffman Plexi 6V6 schematic and layout do not use a tube rectifier, and I plan on doing so. What changes to the layout do I need to make?
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Don't install the two diodes in the lower right corner of the board. Connect the PT red wires to pins 4 and 6 of the rectifier socket. Run a wire from pin 4 of the rectifier socket to the bottom of that 220K/3W resistor on the right side of the board. Run a wire from pin 8 of the rectifier socket to the turret in the lower left corner of the board (the turret that no longer has a diode on it). If you want a STBY switch, put it between pin 8 of the rectifier socket and the board. That should be all.
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Don't install the two diodes in the lower right corner of the board. Connect the PT red wires to pins 4 and 6 of the rectifier socket. Run a wire from pin 4 of the rectifier socket to the bottom of that 220K/3W resistor on the right side of the board. Run a wire from pin 8 of the rectifier socket to the turret in the lower left corner of the board (the turret that no longer has a diode on it). If you want a STBY switch, put it between pin 8 of the rectifier socket and the board. That should be all.
sluckey, like this?
(http://img.photobucket.com/albums/v376/fpaxton/IMG_1115%20with%205U4_zpsxji8rx0x.jpg)
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yes
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Remember to make your cap can connections at ABCD, which are not shown here but are elsewhere.
What rectifier tube are you planning on using?
Some tube rectifiers can be sensitive to the value of the A node E-cap.
You want to make sure your rectifier is OK with that A node cap's uF value.
The other nodes should be good with Doug's cap can values.
This is a very nice sounding amp, IMO. :icon_biggrin:
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Remember to make your cap can connections at ABCD, which are not shown here but are elsewhere.
What rectifier tube are you planning on using?
Some tube rectifiers can be sensitive to the value of the A node E-cap.
You want to make sure your rectifier is OK with that A node cap's uF value.
The other nodes should be good with Doug's cap can values.
This is a very nice sounding amp, IMO. :icon_biggrin:
I'm planning on using the same 5U4 rectifier tube that the original AO-29 had. I'm also going to use the original PT & OT, with the addition of that Mercury Magnetics Fender choke.
I'm dropping the "bright volume" pot from the Plexi 6V6 layout as well, and will run the 470k resistor from the volume middle lug straight to pin 2 of V2. So, since I am doing that and therefore eliminating the shielded wire that goes to the turret board and hooks up to a .0022 capacitor, I can eliminate that cap also, correct?
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For me, I just went with Doug's 1 input 2 volume control and Master volume plan exactly.
I like the flexible tone you can get mixing the 2 input signals.
I definitely wouldn't modify that just to drop a shielded wire, pot, and cap.
But it is your amp, and you can make it how you want.
As long as you can deal with any issues your modifications may cause. :dontknow:
Attached is a snip from the 5U4GB Data Sheet.
It indicates 40 uF as the limit for the input cap.
I think Doug's cap can is all 50 uF if I recall correctly.
Maybe one of the more experienced moderators can give you better guidance on the 5U4's input cap specification?
I wouldn't want you to burn up any 5U4s charging up an over value input E-cap.
I know a SS rectifier doesn't have problems with higher value input E-caps.
I'm not certain on what a 5U4 will let you get away with using as an input cap. :dontknow:
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Neither Doug's cap can nor his layout has any 50µF filter caps.
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Sluckey is right, Doug's cap can is 40/20/20/20.
Too many amp PS's getting confused in my mind.
I should have checked the plans 1st.
So the 40uF is fine for the 5U4 or 5AR4.
But swapping in a 5Y3, 5R4 or 5V4 instead, might not be good. :dontknow:
Those do seem to want a lower value input cap.
Maybe it's still OK, I tend to use a SS rectifier.
Cheaper, easier, less space used.
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For me, I just went with Doug's 1 input 2 volume control and Master volume plan exactly.
I like the flexible tone you can get mixing the 2 input signals.
I definitely wouldn't modify that just to drop a shielded wire, pot, and cap.
But it is your amp, and you can make it how you want.
As long as you can deal with any issues your modifications may cause. :dontknow:
Couple of reasons for dropping the Bright Volume.
1. In order to have sufficient space between the knobs and with the OT being where it is, I don't want to jam all the knobs too close to each other.
2. Never had one before, so I won't really miss it.
3. Since deleting it, I know I'm losing 1/2 of a 12AX7 (V1), so I'm going to wire that half in parallel with the other half by jumpering pins 2 to 7, 1 to 6, and 3 to 8 (4 & 5 are already jumpered), while keeping everything else the same. I should get more gain this way. Correct?
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1. It seems as if you have the space to follow the plans.
I moved the presence pot to the back near the output jack, that seemed easier to me.
2. You never know what you might be missing if you don't try it.
3. I'm just a rusty old repair tech trying my best to learn this design stuff.
Most modifications I make are to try to use my old vintage junk parts safely and efficiently.
I've got many more years of trial and error experimentation to do before I could answer that question properly. :dontknow:
There are many other members here that could answer most all our questions with authority. :worthy1:
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Couple of update pics.
Got the new grill cloth put on:
(http://img.photobucket.com/albums/v376/fpaxton/8F06CA12-9DF7-4DE3-A1A1-E49D938E7A06_zps1zixgpu7.jpg)
And a nice Weber Silver Bell:
(http://img.photobucket.com/albums/v376/fpaxton/B36B8EB8-A68B-4344-8F9A-AD5928114F86_zpsqiwxzaoy.jpg)
It's looking fairly good so far!
I rounded all the squared corners with my router. Stained it as close as I could to match the rest.
I've got a few minor details to do to button up the cabinet, and by the time that's done, I'll be ready to tackle the chassis.
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I've been busy again!
I got the stuff to make my board and several items for the chassis.
So, I went from Doug's original board drill guide:
(http://img.photobucket.com/albums/v376/fpaxton/0DF8BD05-7C28-4512-AB47-DC0CBD61DA75_zpsdpmekh6w.jpg)
And because the dimensions of the board are different from his to what I need, I converted that to this:
(http://img.photobucket.com/albums/v376/fpaxton/A08F5C04-5012-4322-ACA2-916492C58442_zpskhy1wfny.jpg)
I taped that drill guide to my board material and after center punching and drilling, I ended up with this:
(http://img.photobucket.com/albums/v376/fpaxton/11F09A4D-5926-4A0E-A317-C820CA8B94F3_zpssmpsf6il.jpg)
Not totally perfect, I know, but close enough! Eh?
I decided to go with eyelets, rather than turrets. A local amp builder that I know very well said he prefers eyelets, so that's the way I went.
So far, so good!
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Two of the lugs for the bias pot are definitely close enough. :icon_biggrin:
I'm surprised that you chose eyelets over turrets. I bet if you did a poll on this board that turrets would be favored over eyelets.
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Two of the lugs for the bias pot are definitely close enough. :icon_biggrin:
I'm surprised that you chose eyelets over turrets. I bet if you did a poll on this board that turrets would be favored over eyelets.
I was very torn on the turrets/eyelets decision. I believe, hands down, that turrets would be easier to work with. But my amp builder friend said that he prefers the sound of eyelets over turrets. That's why I went the eyelet route. He must have hearing like Eric Johnson. I doubt that anyone, other than those two, would be able to tell any difference!
At this point, I'm almost done with the cabinet. I'm going to start assembling the main chassis components next.
I will then order all new caps and resistors from Doug and get it all wired up.
Hopefully, it will actually work! :huh:
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But my amp builder friend said that he prefers the sound of eyelets over turrets.
:huh: No wonder I can never quite get the sound right. I'm changing out my turrets this winter. Is it just the ones in the signal path or should I just change all of them? :dontknow:
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:laugh: All that work down the drain. :BangHead:
(One very famous tube amp guru said he could hear the difference in sound between different colored PVC wire insulation.)
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I've heard that clear insulation has the most transparent sound. Adds zero coloration to the sound.
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OK. OK....
You jokey jokesters... :laugh:
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:wink:
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I think you will find the turrets easier to solder on and place the components.
Especially if you want to tweak things and or change/replace failed components.
With those type of eyelets the board tends to burn and the eyelet loosen from multiple solder applications. :icon_biggrin:
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Major components are installed:
(http://img.photobucket.com/albums/v376/fpaxton/62F6C22B-C873-473C-886A-D319051C68F1_zpsjf1qeqto.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/2BC911F2-347B-4682-9110-A5BE153AD0B1_zpss7jwlund.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/0BA401F3-C3E9-4468-AE34-D495945162FE_zpsrn5cbwyj.jpg)
Its starting to look like an amplifier!
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Looking really good!
Still planning on dropping the bright pot?
There is room for your presence pot next to your output jack. :icon_biggrin:
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I think you will find the turrets easier to solder on and place the components.
Especially if you want to tweak things and or change/replace failed components.
With those type of eyelets the board tends to burn and the eyelet loosen from multiple solder applications. :icon_biggrin:
Actually eyelets are easier to tweak/change parts than turrets.
And the boards don't tend to burn and the eyelets don't loosen from multiple re-heating's any more than with turrets.
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OK, so that's your opinion and I'm wrong again.
If you say so.
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Looking really good!
Still planning on dropping the bright pot?
There is room for your presence pot next to your output jack. :icon_biggrin:
Yes, dropped the Bright pot. :dontknow:
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Yes, dropped the Bright pot.
You don't know what you're giving up.
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Yes, dropped the Bright pot.
You don't know what you're giving up.
You're right, but I've already committed down the path of 6 pots.
Would you give up the Presence pot in lieu of the Bright? I could go that way.
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Presence pot can go on the back near your output jack, and still keep your 6 pots on front. :dontknow:
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Presence pot can go on the back near your output jack, and still keep your 6 pots on front. :dontknow:
I suppose I could do that.
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Would you give up the Presence pot in lieu of the Bright? I could go that way.
Absolutely! Being able to blend the bright channel with the normal (dark) channel is a big part of the plexi mojo. You'll probably diddle with the presence pot for about a week then it will likely be left alone.
However, you could probably put the presence pot on the front panel if you like. The presence pot is in the NFB loop which comes from the OT, so no worries about the pot being mounted right over the OT. I'd do it in a heartbeat.
Or, you could put it on the rear panel next to the speaker jack and even simplify the wiring by mounting R26 directly between the speaker jack and the pot.
Bottom line, that bright channel has much more tone value than that presence pot.
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Would you give up the Presence pot in lieu of the Bright? I could go that way.
Absolutely! Being able to blend the bright channel with the normal (dark) channel is a big part of the plexi mojo. You'll probably diddle with the presence pot for about a week then it will likely be left alone.
However, you could probably put the presence pot on the front panel if you like. The presence pot is in the NFB loop which comes from the OT, so no worries about the pot being mounted right over the OT. I'd do it in a heartbeat.
Or, you could put it on the rear panel next to the speaker jack and even simplify the wiring by mounting R26 directly between the speaker jack and the pot.
Bottom line, that bright channel has much more tone value than that presence pot.
OK, you & Paul talked me into putting the presence pot on the back.
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Sluckey is absolutely right about diddling that pot. :worthy1:
The only time I ever adjust it is if someone want to hear just how rough and nasty my Plexi can get.
Otherwise it is set mid range and forgotten about.
The salvaged pots of that value I have are all screw driver type with a locking nut.
The bright pot seems to be the one that I adjust the most often.
It gives just the right edge to the distortion tones, IMHO. :dontknow:
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Now that I'm putting the finishing touches on the cabinet, I have a question for you guys.
To add a little detail to the cabinet, I decided to run some green piping around the perimeter of the speaker baffle.
Should I also run the piping around the actual speaker/grill cloth area? Or no?
With
(http://img.photobucket.com/albums/v376/fpaxton/057EC55B-2659-4A8B-B115-E38DFC0C5FCC_zps3jole4re.jpg)
Without
(http://img.photobucket.com/albums/v376/fpaxton/6F2B46DA-E71C-46A7-8882-10FA26ED8644_zps8piwmu0q.jpg)
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A sneak peek of what it will look like:
(http://img.photobucket.com/albums/v376/fpaxton/8EDBE077-6345-48B5-8D26-1430107D8E7A_zps0u4prad7.jpg)
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You are way past the best looking amp I have ever built. :worthy1:
My 1st Plexi is still naked, looking like a homely hobbled together science fair project. :l2:
But, everyone who has ever heard or played it has said it is a very nice sounding amp. :icon_biggrin:
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You are way past the best looking amp I have ever built. :worthy1:
My 1st Plexi is still naked, looking like a homely hobbled together science fair project. :l2:
But, everyone who has ever heard or played it has said it is a very nice sounding amp. :icon_biggrin:
Thank you Paul!
This is the first time I've ever built an amp. I built a 2x12 extension cabinet before, but this is, by far, the most aggressive undertaking I've ever attempted.
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A few more pics of it nearly done:
(http://img.photobucket.com/albums/v376/fpaxton/782357E6-106F-4F48-823D-1B79AAB9E72E_zpsgnvrx7kq.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/AB0F41A4-9A2C-4F7F-9E39-5E60F9CBB761_zpshmjplmmy.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/D3A28630-8751-43A8-9E3E-643A0ED779CD_zpsa8lv2jnf.jpg)
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That looks great to me! :worthy1:
I think you will be very pleased with what you have created!
As you get closer to firing her up the excitement builds.
Please don't let that excitement cause you to rush or overlook things,
as it has done to me before.
Take your time, and do the highlighter tracing verification of your work. Use your meter to check every line on that diagram.
Ensure your - bias voltage is present at pin 5 of your 6V6 tube sockets before you ever put them in.
Set it at the highest - voltage your pot will adjust to at 1st.
That will keep you from red plating your tubes, and give you some time to verify your voltage readings throughout the amp.
I had a leaky cap on my PI when I 1st fired mine up. That might have caused 1 of my 6V6s to red plate if I had not set the bias so negative.
I had time to record all my voltage readings and compare them to the schematic without causing any harm to my tube.
It was very obvious from the voltage reading at that 1 point, that something was not right. The amp did make sound at this point.
But I was not tempted to just start playing it because I knew something was wrong.
I quickly identified and replaced that leaky cap and all voltages were then good.
Then I adjusted the bias down to what I wanted, and tried her out.
It sounded great and I haven't had any other problems with it yet.
If something doesn't seem right, or you need help.
Post your questions here, and someone will usually give you very good advice rather quickly. :icon_biggrin:
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My 2c : it doesn't need the piping around the speaker.
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OK, so since I am adding the Bright Volume in and moving the Presence pot to the back, the layout shows a 3 lug terminal strip for the Bright Volume (of which, only 2 of the 3 lugs are used).
Due to the lack of space in my narrow chassis, I could mount the terminal strip right onto the eyelet board where there is some room right next to the Bright pot. OR, I can add eyelets right in that same spot and that would accomplish the exact same thing, wouldn't it?
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Terminal strip can be eliminated, sort of.
Take a look at this pic, and remember it's my 1st science fair salvaged parts Plexi. :l2:
Those parts can kind of be joined together, floating in a sort of point to point wiring way.
I'm sure you will probably figure out a nicer prettier way than I did on this, but it works fine. :l2:
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Paul I sent you a PM and have not received a reply. :dontknow:
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Question:
When wiring in the Bright Volume, I'll be using the RG174 shielded wire.
In the image below, it looks like at the pot, I hook the hot to the lug and ground the shield. YELLOW CIRCLE
Now at the board, to I just wire the hot to the turret (eyelet, in my case) or what? BLUE CIRCLE
(http://img.photobucket.com/albums/v376/fpaxton/IMG_1155%20bright%20volume_zpsvujnah2y.jpg)
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Now at the board, to I just wire the hot to the turret (eyelet, in my case) or what? BLUE CIRCLE
yes
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You got it right. Only signal wire at the board.
Signal wire at the pot, and shielding Gnd wire to what I call a Gnd bus wire at the pots.
If you look closely at that last pic, you will maybe see that.
And you will maybe notice I had already had swapped my Gnd and signal connections because I had wired it up backwards the 1st time. :l2:
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Very good on the signal to eyelet only.
Now, here's yet ANOTHER question!
In this image, this thing labeled "feedback" has me confused. Do I run a wire from the board to the speaker jack? I'm not using an impedance selector.
(http://img.photobucket.com/albums/v376/fpaxton/0D420302-AD68-46B6-A9E9-A5BDD586FBC8_zps3ogmrq5w.jpg)
Also, by looking at my modifications/adaptations, does everything look copacetic?
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"feedback" has me confused. Do I run a wire from the board to the speaker jack?
yes
does everything look copacetic?
rectifier tube looks good. I don't understand why you crossed out the center tap ground connection on the PT red winding? That CT must be connected to ground. Concerning your power inlet wiring... White wire is used with Neutral, black wire is used with line. If you are just using a power cord, then connect the black to the fuse and connect the white directly to the PT. And green to a dedicated chassis bolt with no other ground connections.
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Looking good.
The only thing left for you to maybe consider since you are using a tube rectifier, is the "Immortal Amp" mod?
Basically, it just adds 2 diodes to your rectifier socket to help protect your PT.
It is very cheap insurance, IMHO. :icon_biggrin:
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"feedback" has me confused. Do I run a wire from the board to the speaker jack?
yes
does everything look copacetic?
rectifier tube looks good. I don't understand why you crossed out the center tap ground connection on the PT red winding? That CT must be connected to ground. Concerning your power inlet wiring... White wire is used with Neutral, black wire is used with line. If you are just using a power cord, then connect the black to the fuse and connect the white directly to the PT. And green to a dedicated chassis bolt with no other ground connections.
The PT has a green cloth insulated wire that went to ground. I was told to take that wire & the green cord wire and put terminal lugs on them and ground them to the same spot, like one of the corner PT bolts.
That red wire that I crossed off, originally went to the field coil connector that then connected to the FC speaker. Since I am now going to use a permanent magnet speaker, I didn't figure that wire to be of any use, especially since I have that green grounding wire from the PT.
From power cord, black to fuse, then on/off switch, then to PT. White direct to PT. And green to the aforementioned ground.
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Looking good.
The only thing left for you to maybe consider since you are using a tube rectifier, is the "Immortal Amp" mod?
Basically, it just adds 2 diodes to your rectifier socket to help protect your PT.
It is very cheap insurance, IMHO. :icon_biggrin:
Paul, can you give me more specifics? What type diodes and where do I connect them?
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Time to learn how to use the search feature here. :l2:
You will find the info on other threads here, no need for a rehash.
It is a very simple mod, and after you read about it, if you still have questions someone will square you away. :icon_biggrin:
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Time to learn how to use the search feature here. :l2:
You will find the info on other threads here, no need for a rehash.
It is a very simple mod, and after you read about it, if you still have questions someone will square you away. :icon_biggrin:
Gothca.
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That red wire that I crossed off, originally went to the field coil connector that then connected to the FC speaker. Since I am now going to use a permanent magnet speaker, I didn't figure that wire to be of any use, especially since I have that green grounding wire from the PT.
The green wire from the PT has nothing to do with this center tap wire. It's not optional. ***YOU MUST CONNECT THAT CENTER TAP TO SOMETHING!*** You will have NO B+ voltages if you don't connect that wire to something. Now you can connect that CT directly to ground and your B+ will be about 100V higher than you will want. Or, you can connect a 700Ω 30 watt resistor between that wire and chassis to simulate the missing field coil.
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> I run a wire from the board to the speaker jack?
Yes. We want the amp to "know" what is happening at the speaker.
Impedance tap is not so fussy. It looks like the plan taps off the 8 ohm winding, so if you have 8 use that. But 4 or 16 is not so different. And in the final stage, tweaking the amp to a speaker and a player, you should try different values for the "feedback" resistor. Looks like 47K? Try (in your near-final form) 22K and 100K against 47K. Higher values give more gain and more flavor, lower values less gain and more polite.
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That red wire that I crossed off, originally went to the field coil connector that then connected to the FC speaker. Since I am now going to use a permanent magnet speaker, I didn't figure that wire to be of any use, especially since I have that green grounding wire from the PT.
The green wire from the PT has nothing to do with this center tap wire. It's not optional. ***YOU MUST CONNECT THAT CENTER TAP TO SOMETHING!*** You will have NO B+ voltages if you don't connect that wire to something. Now you can connect that CT directly to ground and your B+ will be about 100V higher than you will want. Or, you can connect a 700Ω 30 watt resistor between that wire and chassis to simulate the missing field coil.
OK, so if I put a 700 ohm / 30 watt resistor between that red center tap and the chassis, and the green still goes to ground? Or do I not use it at all?
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and the green still goes to ground?
yes
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Or, you can connect a 700Ω 30 watt resistor between that wire and chassis to simulate the missing field coil.
I've been doing some internet searching for such a beast and am coming up empty. Where can I get one?
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http://www.mouser.com/ProductDetail/Vishay-Dale/RH050700R0FE02/?qs=sGAEpiMZZMtTURnxoZnJAHlhF1kLzuAqgg5mGcFi6Kw%3d (http://www.mouser.com/ProductDetail/Vishay-Dale/RH050700R0FE02/?qs=sGAEpiMZZMtTURnxoZnJAHlhF1kLzuAqgg5mGcFi6Kw%3d)
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> searching for such a beast
Three 2.2K 10W in parallel.
Three 750r 10W in series.
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> searching for such a beast
Three 2.2K 10W in parallel.
Three 750r 10W in series.
Good to know! Thank you
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Mail came today! Nice Fender Brown Face knobs!
(http://img.photobucket.com/albums/v376/fpaxton/2CB29CF3-F7E6-4452-A121-9144333C3005_zpslrztblkv.jpg)
It's starting to take shape! In a couple of weeks, it will be DONE! I'm excited, to say the least!
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Lesson learned.
I should have used turrets instead of eyelets.
-
Two questions:
1. The schematic shows a couple of things going to "E" on the board. But the layouts show nothing going to "E". How do I reconcile this?
Schematic:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_1190%20E_zpsowky0yo8.jpg)
2. When attaching the PT to the heaters, the photos of Doug's build (which he said are of the prototype and in some cases should not be used as a guide) show something like this:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_1189%20Heaters_zpsjw67vbfn.jpg)
This is from PT to V5 pins 2 & 7 to V4 pins 2 & 7 and then from V4 pin 2 to V3, V2 and V1 pin 9 (in series?) and V4 pin 7 to V3 pin 5, V3 pin 4 to V2 pin 5 then V2 pin 4 to V1 pin 5 with V1 pin 4 open.
Is this the correct way to do this? Please advise.
Thanks, as always!
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> things going to "E" on the board. But the layouts show nothing going to "E".
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> things going to "E" on the board. But the layouts show nothing going to "E".
Thank you.
After seeing that pic and looking again at the schematic, I see that the layout is correct.
You are a great help, PRR!
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Lesson learned.
I should have used turrets instead of eyelets.
Why? :dontknow:
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Lesson learned.
I should have used turrets instead of eyelets.
Why? :dontknow:
In some cases, 3 wires will not fit into an eyelet.
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Are your using stranded wire and large 16g, 18g?
I've done a few boards where I used both eyelets and turrets. I used the turrets where I had a lot of wires going to 1 termination point. It worked well for me.
I've also have used turrets to lift parts above other parts when crossing over at 90 degrees.
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Are your using stranded wire and large 16g, 18g?
I've done a few boards where I used both eyelets and turrets. I used the turrets where I had a lot of wires going to 1 termination point. It worked well for me.
I've also have used turrets to lift parts above other parts when crossing over at 90 degrees.
Solid wire, 20g. 3 just don't like to fit.
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Under V3 in purple on the board there is a connection for that Feedback resistor.
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Couple MORE questions!
1. In the layout, what is the relation between the Bias Tap & Bias Range?
(http://img.photobucket.com/albums/v376/fpaxton/Plexi6V6layoutBias_zpshihdusbo.jpg)
2. Since the pots are all attached to the chassis (which, in my my mind grounds them), do I really need to run a grounding wire across the back of them all? Or should I just ground the appropriate lugs to the backs of the pots?
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1. Bias tap denotes the AC voltage source for the bias circuit, in your case, the top side of the HT winding. Bias tap could be a dedicated 'tap' on the HT winding, a totally separate secondary winding, or even another PT specifically for bias. Bias range refers to a resistor that you can change the value if your bias adjustment range needs to be raised or lowered to suit your particular tubes. You may have to change the value of that resistor since you are using an oddball PT.
2. You don't have to connect that ground buss to the back of the pots. It's a personal choice. Hoffman does, I don't. But in either case, the ground buss will provide a more reliable ground connection than just soldering the pot lug to the back of the pot. I know that Fender did this, but he also had a brass plate sitting under the pots. This brass plate served as a ground buss but it was prone to problems due to dissimilar metals. I advise you don't solder the lug to the back of a pot.
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Thanks sluckey. Comments in color in the quote section:
1. Bias tap denotes the AC voltage source for the bias circuit, in your case, the top side of the HT winding. Bias tap could be a dedicated 'tap' on the HT winding, a totally separate secondary winding, or even another PT specifically for bias. Bias range refers to a resistor that you can change the value if your bias adjustment range needs to be raised or lowered to suit your particular tubes. You may have to change the value of that resistor since you are using an oddball PT. So, there is no wire that connects those two. The labels on the layout are for reference. Correct?
2. You don't have to connect that ground buss to the back of the pots. It's a personal choice. Hoffman does, I don't. But in either case, the ground buss will provide a more reliable ground connection than just soldering the pot lug to the back of the pot. I know that Fender did this, but he also had a brass plate sitting under the pots. This brass plate served as a ground buss but it was prone to problems due to dissimilar metals. I advise you don't solder the lug to the back of a pot. I understand. I'll stick with the layout. Since the Presence pot is now on the opposite side of the chassis, would it suffice to just have that one with the lug grounded to the back of the pot?
That Center Tap wire from the PT that I was originally not going to use... I'm going to get that behemoth resistor from Mouser, but (like any other resistor I've seen, it has two terminal points. Does the CT go to one, and the other to ground? Or what?
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So, there is no wire that connects those two. The labels on the layout are for reference. Correct?
That's correct.
Since the Presence pot is now on the opposite side of the chassis, would it suffice to just have that one with the lug grounded to the back of the pot?
No. Run a wire to your power ground point, probably a PT bolt. Soldering a pot lug to the back of the pot is not a reliable ground connection IMO.
Does the CT go to one, and the other to ground?
Correct.
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So, there is no wire that connects those two. The labels on the layout are for reference. Correct?
That's correct.
Since the Presence pot is now on the opposite side of the chassis, would it suffice to just have that one with the lug grounded to the back of the pot?
No. Run a wire to your power ground point, probably a PT bolt. Soldering a pot lug to the back of the pot is not a reliable ground connection IMO.
Does the CT go to one, and the other to ground?
Correct.
Man, I've got a shitload of things to ground!!
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I ordered the last parts I'll need (hope upon hope) for this thing: the resistors and caps that go directly onto the board.
Since this is my first try at this, I'm actually quite frightened to plug the thing in! I'd really hate to have it blow up or catch my house on fire. My wife would be even more angry. That'd probably push her over the edge to divorce-ville. That'd sure suck.
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I made a simple light bulb current limiter to use when starting up my last amp. They are very simple to build and you will be able to tell if you have a direct short. its just a short extension cord with a light bulb in series with either the black or white wire in your extension cord. Their may be a plan here in the amp library section here on this site, if not you can just google it and there are tons of examples online.
Here I found a drawing:
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I made a simple light bulb current limiter to use when starting up my last amp. They are very simple to build and you will be able to tell if you have a direct short. its just a short extension cord with a light bulb in series with either the black or white wire in your extension cord. Their may be a plan here in the amp library section here on this site, if not you can just google it and there are tons of examples online.
Here I found a drawing:
Very cool! I had recently seen one of these, but wasn't quite sure how it worked or if it even applied to me.
Thanks!
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A little more progress today:
(http://img.photobucket.com/albums/v376/fpaxton/01AF212B-CBB7-4876-ACCF-1C80FEC5BFE6_zpsawwk4jkl.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/EEED3E34-7304-4348-9EEC-DFDE3B04F0AD_zpsbk3p9zng.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/8CF58C28-B538-4927-9DB4-E597C165639F_zpshub20t7b.jpg)
(http://img.photobucket.com/albums/v376/fpaxton/F5B53A87-2C30-43F7-9004-667F4B0C687D_zpso4cbaip9.jpg)
Good old DYMO label maker. Comes in handy every once in a while! :icon_biggrin:
Just waiting for the last few parts to come in and by mid-week, I should be firing it up (and likely trying to figure out what I did wrong OR what's not working!). Yes, I have very little faith in this, my first attempt!
But, I will say that my soldering skills have gotten MUCH better from when I first started fooling around with pickup swaps, etc. Back then, I was the undisputed KING of the cold solder joint! :worthy1:
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When attaching the PT to the heaters, the photos of Doug's build (which he said are of the prototype and in some cases should not be used as a guide) show something like this:
(http://img.photobucket.com/albums/v376/fpaxton/IMG_1189%20Heaters_zpsjw67vbfn.jpg)
This is from PT to V5 pins 2 & 7 to V4 pins 2 & 7 and then from V4 pin 2 to V3, V2 and V1 pin 9 (in series?) and V4 pin 7 to V3 pin 5, V3 pin 4 to V2 pin 5 then V2 pin 4 to V1 pin 5 with V1 pin 4 open.
Is this the correct way to do this? Please advise.
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That's fine. Don't forget the jumpers between pin 4 and 5 on ALL little tubes.
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That's fine. Don't forget the jumpers between pin 4 and 5 on ALL little tubes.
Got it. Thanks again!
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Started on the eyelet board.
Any concerns?
(http://img.photobucket.com/albums/v376/fpaxton/5A1ECCDF-01B5-4629-9BD1-6F2D3B11173E_zpsbpq5yjbv.jpg)
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It appears to me that your big black E-cap is installed backward. :dontknow:
And the little blue one too. :w2:
Another suggestion for your heater wires.
Since these are usually VAC we tend to twist them together to help cancel hum.
You have used brown wires.
I usually would use something like a brown wire and a brown with white stripe wire.
To twist them up easily you can put these 2 wires in your drill like a drill bit and tighten it down.
Then just slowly squeeze the trigger and nicely twist up a decently long string of these wires.
I then try to cut them just a little longer than needed to reach between the sockets.
Untwist just enough on each end to make a clean connection at the socket.
It's debatable if it is necessary or not, but putting the white stripe wire on 4-5 and brown on all 9s seems to at least look organized. :icon_biggrin:
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It appears to me that your big black E-cap is installed backward. :dontknow:
And the little blue one too. :w2:
I'm pretty sure the black one is, but I will check them both.
How about the buss wire that runs from eyelet to eyelet? Should I have put that on the other side of the board? Any potential concerns there?
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In this, Doug's layout is shown by the black line.
I have it wired like the green.
Is there any difference?
(http://img.photobucket.com/albums/v376/fpaxton/IMG_118920Heaters_zpsjw67vbfntone_zpsirsgflbi.jpg)
Also, on the pic above of my board (with the upside down filter caps, that I will fix), am I OK with the buss wire one the top side of my board? Are there any problems or potential problems with it this way?
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Is there any difference?
Yes. Your green wire is longer than Doug's black wire. :icon_biggrin:
am I OK with the buss wire one the top side of my board?
yes
Are there any problems or potential problems with it this way?
no
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OK!
I am 99.9% sure that I've got everything done correctly (hope upon hope!)
Here's a pic. Could you guys look at it and tell me if it all looks alright to you?
(http://img.photobucket.com/albums/v376/fpaxton/25F95E44-C6D1-4457-9569-4109E9B7746D_zpsemgt7u5i.jpg)
I redid the heater wiring like Paul suggested and got my caps now oriented the correct way. I continuity tested everything that I could think of and got positive results from that.
All I need to do now is put the tubes in and plug it in, I think!
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I made a simple light bulb current limiter to use when starting up my last amp. They are very simple to build and you will be able to tell if you have a direct short. its just a short extension cord with a light bulb in series with either the black or white wire in your extension cord. Their may be a plan here in the amp library section here on this site, if not you can just google it and there are tons of examples online.
Here I found a drawing:
Don't forget the light bulb limiter for 1st start up. Here's another link from Sluckey's web site that has some instructions on how to use it;
http://sluckeyamps.com/misc/Amp_Scrapbook.pdf (http://sluckeyamps.com/misc/Amp_Scrapbook.pdf)
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OK!
It makes good sounds!
Nothing exploded!
I didn't get electrocuted nor burn my house down!
It's not entirely done yet, but here's what I've got so far:
(http://img.photobucket.com/albums/v376/fpaxton/308708C2-0204-4FDC-8D0C-3698A647FF15_zpsmbci2uhq.jpg)
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Don't it feel good!
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Don't it feel good!
An incredible sense of accomplishment!
Thanks to EVERYONE who helped me!
After this on is completely done, I wonder what I'll build next? :dontknow:
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What you have built also has a very cool old school appeal to it, IMO.
Not a sterile metal and plastic look, but a hand crafted woodworking style! ;^)
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What you have built also has a very cool old school appeal to it, IMO.
Not a sterile metal and plastic look, but a hand crafted woodworking style! ;^)
Well, the organ was made like a piece of furniture (for that time) and that was the look I was after.
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Awesome! Good Job!! :icon_biggrin:
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Sooooo, never being quite satisfied with things, I started messing around with it today.
I was liking the tone from the 6V6's, but not the volume. With the volumes dimed, it was above bedroom level, but well below band practice level.
So I put these in :think1::
(http://img.photobucket.com/albums/v376/fpaxton/54AC3F23-F088-4507-864F-B4E85513DBBD_zps5phfweqb.jpg)
:icon_biggrin: :icon_biggrin: :icon_biggrin: :icon_biggrin:
I biased it a tad cooler than the 6V6's but still enough to give it some oomph.
HOLY COW! This little amp absolutely came ALIVE! The tone is even better than the 6V6 variant, and it now has a nice set of balls!
I am over the MOON with this thing now!!
(http://img.photobucket.com/albums/v376/fpaxton/9577D28B-020A-4DF2-83F8-A959F795CD8D_zpssueptwyl.jpg)
Yes, the 6L6's are a tad close to one another, but then, the choke is a tad close to the PT. Not ideal, but it is what it is.
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6L6 are large tubes for an amp producing more watts. If you have the amp designed for 6v6 voltages and bias settings you may want to wait for PRR or Sluckey to advise whether it is safe or if you will soon see smoke. LOL
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Almost done.
(http://img.photobucket.com/albums/v376/fpaxton/BF207AC6-3873-4A78-B374-F821291F9713_zpsubyd5vxt.jpg)
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This is great - I too have an A029 and FC Speaker. Has anyone used one of these FC in any of their builds?
So - the 6L6's worked out well?
Excellent work, my friend! :nice1:
It's great that you did such a nice documentation.
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Holy thread resurrection, Batman!
Well, due to some circumstances that have happened in my life, I did not have this amplifier for about 6 months. I just got it back last week and it had been sitting, doing nothing during all that time.
When I fired it up, I notice that the volume seems to be a bit down, meaning less volume than I remember. The 2 6L6's ought to be PLENTY loud, especially in the bedroom, but I really have to crank it in order to get some halfway decent volume out of it. I remember it being plenty loud at mid level volume settings, but now I have to dime everything to get it going.
Any ideas on what could have gone wrong? All the tubes are glowing when I turn it on.
As an aside, it looks like Photobucket wants to charge me $400 per year in order to enable 3rd party hosting. I think that's complete bu11sh!t. Plus, their site seems to take FOREVER to load or do anything. Time for a change. Any suggestions?
Again, thanks to all who helped me on this amp. I really love it!
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This forum supports attachments of reasonable size. There is a sticky post discussing image down-size techniques.
postimg.org and imgur.com are simple no-BS image hosts.
> what could have gone wrong?
Can't see it from here. Whoever is closest should be checking voltages.
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Can't see it from here. Whoever is closest should be checking voltages.
Yes, I realize that a physical inspection would be best.
All I'm asking is for a point in the right direction.
I can check voltages, etc. I just don't know where to start, or what components would be the most likely of culprits.