Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Misc Schematics and Layouts => Topic started by: Imntgrumpy on December 12, 2006, 10:07:31 am
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/me This post has gotten really long and hard to sift through for the diagrams. I added a condensed post here with just the diagrams.
http://www.el34world.com/Forum/index.php?topic=4770.0
Hey guys,
I've just started my new build. I'm doing a Princeton Reverb Clone. I was hoping to use a Hoffman style layout but I can't seem to find one.
I've use the AB763 in my last build it's similar upto a point. I'm sure I can figure the layout by myself but I don't want to re-invent the wheel if I don't have to.
Anyone got a Hoffman style layout for the AA1164 Circuit?
Thanks
Jim
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Hotblue,
That's exactly how I did my first build. It was a Deluxe Reverb Clone. It took me about six months of study and homework to complete the task. It was well worth it.
Now I'm starting on this new project. I like to build as much as I can from scratch. I get a lot of satisfaction out of it. I just completed bending the chassis out of .020 Aluminum.
Don't knock yourself out. I appreciate the offer. I'll try to do the layout on my own. If I'm successful, I'll post it here for others to use.
Thanks
Jim
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HBP, what kind of bribery would it take to get you to cook up a Hoffman style layout for a 5F2 or 5F2-A or your own version of something in between?
Those Fender layouts intimidate me.
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Don't knock yourself out. I appreciate the offer. I'll try to do the layout on my own.
I've got it about half done right now... Drawing/editing the Hoffman layout in Windows Paint is the slow part.
HBP, what kind of bribery would it take to get you to cook up a Hoffman style layout for a 5F2 or 5F2-A or your own version of something in between?
Wouldn't be hard. Like I said, drawing it is the slow part. I really wish I had a scanner at this point because I could hand draw something quick.
Now here's the question... Do you guys have Hoffman's drilling template (meaning the aluminum plate with the grid of holes)? I ask because while I can draw something relatively quickly, the layout image might not be to perfect scale. I know some guys like to print off a life-size copy of the layout and use that for drilling, but it's imprecise and assumes everything on the drawing is to scale (which it never is). If you have the template, you can double-check turret spacing with physical parts and decide where the best spacing is.
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HotBlue,
No on the Drill template. On may last build I printed the Hoffman layout on peel and stick paper. I only exposed several spots on the sticky side of the paper to ensure adherence to the board. I then stuck it on the Fiberglass and drilled where appropriate. Finally, I removed the paper from board. It came out quite well.
Since I'm only doing one or two amp per year this method works well enough.
Thanks
Jim
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HBP: I don't have the template, but I'm building one amp at a time. I figure out the spacing on paper or paint and then make the board from there. I just would kill for an easy to read and understand Hoffman type layout.
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Well, give me a few hours on the Princeton Reverb, and then I'll do the Champ. Better yet, check back tomorrow morning.
I can list the approximate spacing for the turrets when I post the layout and from there you can either get the drilling template (if you contemplate making a lot of boards at some point) or adjust the primted spacing accordingly.
You know, I have a feeling I'll get done with this layout and 4 months from now, start seeing "Hoffman Princeton Reverb Kits". ;D
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here's a couple pics of one I built.
You may be able to get a layout by looking at the pics.
(http://www.el34world.com/Misc/images/Dscn1828.jpg)
(http://www.el34world.com/Misc/images/DSCN1848.JPG)
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BTW, I have that princeton reverb board and all the parts here.
I gutted my PR to make my Reverb stout.
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Okay, I've got a layout, including a slight improvement on how the trem oscillator circuit is laid out. But the drawing is the slow part... Of course, you could just buy Doug's populated board and be all set.
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This is really strange!! I have been thinking about a Princeton Reverb also. Some of my friends think it's one of the best for steel guitar (not pedal) HBP are you going to post that layout?? Just before I read this post, I was looking on the Turret boards site. They have a board, but is it the same as the Fender layout?
What about dimensions for the chassis, does anyone list them? I have the equipment to bend up anything I will need.
Regards
BILL
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Just before I read this post, I was looking on the Turret boards site. They have a board, but is it the same as the Fender layout?
I just eye-balled the Turretboards.com Princeton Reverb board. It is the same layout that is used with the original Fender eyelet board, but using turrets instead of eyelets.
HBP are you going to post that layout??
Sure. The drawing is kicking my butt, as I'm having to learn MS Paint to edit a Hoffman layout to be the Princeton Reverb layout. My big concern at the moment is that the Hoffman layout drawings are not exactly to scale, because some turrets get shifted so that the part values can be fit in and around them. Same thing with some of the wiring. Since I know people will just print off the image and use that as a drilling guide, I'd like the spacing of turrets to be right, but that might be too much to ask at the moment.
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HBP; Couldn't the parts/components be laid on the board drawing, and turret positions adjusted for spacing? This may be a dumb question, but I think I would do it that way if the basic layout is available. :-/
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HBP,
I'll be happy to dress up your layout using XFig when you're finished if you like. You can do absolute positioning and get an accurate postscript or PDF printout with it.
For "Win-ders" you can get XFig by installing Cygwin. It's free and works great for doing layouts.
Cheers,
Jerry.
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Are you ready? Here it is! Of course, everyone please double-check this against the schematic, as I had a number of frustrations trying to get it together and I might have overlooked something.
Here's a link (http://i137.photobucket.com/albums/q237/Hotblueplates/HoffmanPrincetonReverba.jpg) to it.
(http://http://i137.photobucket.com/albums/q237/Hotblueplates/HoffmanPrincetonReverba.jpg)
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Well, hell... The uploading process has made it small and fuzzy. Opening with Paint allows me to view it in a plenty-large size, and my copy isn't all blurry. Hmmm....
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HotBlue,
I've been looking over the drawing. Where is the .02 cap shown below on your drawing?
(http://img.photobucket.com/albums/v242/Imntgrumpy/prquest.gif)
Jim
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Hot Blue; Much Aloha for doing the layout. Like you said, it's kind of fuzzy, but values should be verifiable from the schematic.
I don't know how long this board will be yet, but I have a 12 inch piece coming , and a bunch of turrets, so we will see how it goes.
Thanks again BILL
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I don't know how long this board will be yet, but I have a 12 inch piece coming , and a bunch of turrets, so we will see how it goes.
Thanks again BILL
If you use the Hoffman board spacing it will be 13 and 1/4" long. Your 12" board is going to be very tight.
Attention: All drawings are on page two of this thread.
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If you use the Hoffman board spacing it will be 13 and 1/4" long. Your 12" board is going to be very tight.
Well, I've got it laid out on my drilling template, and it's over 12". Once you allow for a little bit of space on the end, you'll want that board to be 13" or a little more. The spacing between lugs in the rows on the drilling template (lengthwise spacing) is about 19/64th's of an inch. Might sound like a lot on here, but bust out a steel rule marked in 64th's and you'll see the turrets are about as close together as you can reasonably make them.
I've been looking over the drawing. Where is the .02 cap shown below on your drawing?
Look at V4 pin 1. Follow the wire from pin 1 to the board, where there is a 1M resistor. The 0.022uF cap in question is right below that resistor, connecting to ground.
Just to confuse you, there is a second 0.022uF cap in the trem circuit, and that is to the right of the 1M resistor where V4 pin 1 connects.
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...you'll want that board to be 13" or a little more.
Yeah that's what I said, 13 and 1/4" ;) I measured your layout on the drilling guide as well. And I second the thanks for doing it.
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HotBlue,
On your drawing should there be a jumper between the .022 cap (V3 pin 6) and the 1M resistor(V4 Pin 7)? If not where do I connect the .022 cap?
Jim
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HotBlue,
I'm really confused. Something doesn't seem right around the V4 Connections.
It seem like you've got an underboard short going from and to pin 1. Fender has a cascade of caps from V4 pin 1. I don't see that cascade. I also don't see the 3.3K/25uf group from V4 pin 3?
Am I missing something?
Jim
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Hot Blue Plates : The drilling template you refer to, is that the Hoffman type in his board parts list??
Oh Yeah, is there a chassis available? Or is there specs or prints of the chassis around?
Bill
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Here I am again with another dumb question: Is this a black or silver face circuit? The silver is the later version isn't it??
I'm looking at chassis and cab requirements.
BILL
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Mojo sells a reproduction Princeton Reverb chassis... It's a nice one too, I bought one a little while back.
It has the big hole for the cap can by the PT, for my application I covered it.
Cheers,
Jerry.
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I'm really confused. Something doesn't seem right around the V4 Connections.
You have to draw it out as shown, then carefully draw what's going on around the oscillator. It's 100% right... I spent more than an hour trying to figure out how to fold that circuit so it didn't take up too much board space. You have to go through it slowly with the schematic, not the original Fender layout or you'll get yourself confused.
Is this a black or silver face circuit?
Blackface. But to my knowledge, the only change for the silverface version was higher supply voltages.
The drilling template you refer to, is that the Hoffman type in his board parts list?
No. What Hoffman calls a "drilling template" is a big aluminum panel with a large grid of holes to guide the drill bit. The "template" Barry has drawn would be called a "drilling mask" by Hoffman, and would show which holes to drill through.
Here is a first attempt at a drilling template. HBP please check for errors.
I'll give it a look shortly.
EDIT: Something was wrong about the V4 connections. I did have the underboard wire in the wrong place. When I typed my reply, I was looking at the sketch I made to figure out the trem layout, which did have the wire drawn in the right place... but I put it in the wrong place in the diagram.
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> The drilling template you refer to, is that the Hoffman type in his board parts list??
"The drilling template ...is a 1/4 inch thick piece of 6061 aircraft aluminum with over 500 holes drilled very precisely by a computer controlled milling machine. ... You will need this tool to become a Hoffman Amplifiers board kit manufacturer. Price: $100.00"
It is super-useful for making really neat boards in good time. You want it if you make a lot of boards, you must own one to represent your product as "Hoffman Boards".
It is serious over-kill for making a few boards for your own use. So what if your holes come out a little scattered... the electrons won't complain. If it offends your eye, you can buy a lot of board, enough for 10 amps, screw-up 9 of them, and still come out ahead.
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"The drilling template ...is a 1/4 inch thick piece of 6061 aircraft aluminum with over 500 holes drilled very precisely by a computer controlled milling machine. ... You will need this tool to become a Hoffman Amplifiers board kit manufacturer. Price: $100.00"
I absolutely love mine. But, I do make a lot of boards, so it has been worth every penny. The last I heard Doug was out of them. Are they back in stock Doug?
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My princeton reverb board is 11-7/8" long.
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My princeton reverb board is 11-7/8" long.
Yes, but your board doesn't include the bias assembly, the 470 ohm screen resistors, the 1 ohm cathode resistors or the 2 100 ohm resistors for the artificial CT on the heater circuit. Of course it's shorter. Take that stuff off and the Hoffman board will only be 11 and 1/4" long. Nice work on the Fender layout though Psycho. I like the red swirl.
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Well the princeton reverb chassis has more than enough room for all those components and the fender layout works just fine.If you make the board so long it will cover up the cap can.
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loaded the board.
Beautiful, beautiful job Barry. I'd love to know what program you're using for drawing the board layouts.
One omission on your final layout: the 100k slope resistor on the tone circuit. Other than that, it's spot on.
I did have an error on my original layout that must be corrected: the 3.3k resistor in the trem oscillator has to have a 25uF (or 22uF) cap across it. Also, although I didn't understand what was being pointed out earlier, the underboard wire in the trem oscillator (where the 0.01uF cap connects to the 1M resistor) goes to the wrong 1M resistor. It should go 1 lug to the left, to the other 1M resistor.
Note that the corrections I mentioned have been made to my original post of the layout.
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loaded the board.
I did have an error on my original layout that must be corrected: the 3.3k resistor in the trem oscillator has to have a 25uF (or 22uF) cap across it. Also, although I didn't understand what was being pointed out earlier, the underboard wire in the trem oscillator (where the 0.01uF cap connects to the 1M resistor) goes to the wrong 1M resistor. It should go 1 lug to the left, to the other 1M resistor.
Note that the corrections I mentioned have been made to my original post of the layout.
HotBlue,
Thanks for pointing out the error. As a Noob, I wasn't quite sure that I was understanding the layout properly.
Jim :)
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If you make the board so long it will cover up the cap can.
Ah yes another beauty of the Hoffman board assembly. Because it's on stand offs that doesn't even matter. Simply run the wires underneath. And of course if you wan't the shorter board, cut out the extra stuff I mention and mount those components in the chassis as you point out. One could modify the Fender layout with the added components as well if one isn't hung up on Holy Grail compliance. ;)
HBP,
Oops, missed that slope resistor indeed. I'll make the changes to the boards tonight. By the way, I'm using Visio 2003 with my own component stencil. It's just drag and drop on most things. I have my Hoffman drilling guide layout converted to digital and I just delete the unused holes for each board. From there I print out a scale drawing and make a mask, or just a board if I'm only doing one amp.
Barry
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Barry,
Did you mean Visio? I use that to make my faceplates and chassis layouts. Would you be willing to share your component stencil?
Can you email the princeton layout in standard Visio format?
Jim
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I just finished making a drilling fixture for the board, out of 6061T6 aircraft aluminum. I copied the layout in two halves and taped them together, doing some measuring to verify the layout came out right. The hole locations were transfered to the aluminum 1/8 inch sheet with an automatic center punch, and all the holes drilled with a 3/32 drill, and deburred. The six mounting holes are drilled for 8-32 screw size. I didn't have any 1/4 inch stock around , or I would have made the fixture thicker. I'm an aircraft mech and have the tooling to do this stuff. I just need to get a longer blank board.
Nice job on the layouts you guys!!!
Regards BILL
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Thanks for pointing out the error. As a Noob, I wasn't quite sure that I was understanding the layout properly.
Yep, you called it. When I said everything was right, I was looking at the sketch I'd made to figure out the layout and not at the actual layout I'd posted. The sketch was right, the layout wrong. The upshot is that I've made the corrections to my layout and posted them in the original post.
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HotBlue,
I'm looking at the original post and still see the same error. Do you have to re-load the image or something?
Jim
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Refresh the page. I deleted the original picture file and replaced it and the link with the new one.
If you have refreshed the page and still see the same error... look very close. The underboard wire didn't go away, it just moved to the left 1 lug. Also, you'll know you have the updated image because the 3.3k resistor in the oscillator circuit now shows a 22uF bypass cap.
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HBP, if space is an issue, you can in fact fit the plate resistor, 0.1, and other resistor all on
one line (in the phase inverter)...
You are using 7 holes left to right for the PI... I think you can comfortably do it in 3.
I did that kind of thing on the 5e9, although it is not the exact same PI, check it here:
http://www.theairtightgarage.com/gallery/5e9a.jpg
Now I know what you are thining "but triode, the 0.022 is much smaller than the 0.1s
in the princeton"... true, but I use the big 0.022s (Jensen/Hovland/etc) and it can be done
without issue, it is just a matter of being in front of the computer with your template on
the table and a few parts in hand.
Just my $0.0001.
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HBP, if space is an issue, you can in fact fit the plate resistor, 0.1, and other resistor all on
one line (in the phase inverter)...
You are using 7 holes left to right for the PI... I think you can comfortably do it in 3.
Yeah, it probably can be compacted. But space is not an issue to me, since I'm not actually building this! ;D
I took my cue from Doug's layout, and from the fact that I wanted to preserve where the ground and B+ busses were.
One thing that amazes me is that people are worried about covering up the hole for the cap can.... Don't worry about it! Do what Doug did and use separate caps. You'll have better control over the grounding of each filter cap that way, and you can place them where it's convenient. If you use Illinois caps like Doug, they will be small enough to fit at the pot buss like he does it. The remaining 2 caps can be mounted on a small board as he does, under the Fender "doghouse" or mounted on terminal strips.
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Refresh the page. I deleted the original picture file and replaced it and the link with the new one.
If you have refreshed the page and still see the same error... look very close. The underboard wire didn't go away, it just moved to the left 1 lug. Also, you'll know you have the updated image because the 3.3k resistor in the oscillator circuit now shows a 22uF bypass cap.
HotBlue,
That did the trick. Now I see the change.
Another question: Shouldn't there be an underboard connections between the .022 cap from V3pin6 to the 1M resistor of V4pin7?
Finally, is there anyway to improve the resolution of the image? Can you save and post it in another format? It's too fuzzy to really read well.
Thanks
Jim
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Shouldn't there be an underboard connections between the .022 cap from V3pin6 to the 1M resistor of V4pin7?
Yes, under the board or above the board. I ought to add that for clarity. EDIT: Just added that as "connection 13".
Finally, is there anyway to improve the resolution of the image? Can you save and post it in another format? It's too fuzzy to really read well.
Unfortunately, no. The image, when uploaded to Photobucket, gets distorted and is fuzzy. The original file is not like that. Unfortunately, I tried to save to a different format, but got the same results. It looks like Photobucket automatically re-sizes it and that re-size makes it blurry. I've just uploaded it again, hoping for slightly better results. It seems a little better, but if you need me to, I'll e-mail the original file. The you can open it in Paint to zoom in on it.
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"One thing that amazes me is that people are worried about covering up the hole for the cap can.... Don't worry about it! Do what Doug did and use separate caps. You'll have better control over the grounding of each filter cap that way, and you can place them where it's convenient."
That's exactly why I covered up the hole in my PR build :)
Cheers,
Jerry.
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Barry,
Did you mean Visio? I use that to make my faceplates and chassis layouts. Would you be willing to share your component stencil?
Can you email the princeton layout in standard Visio format?
Jim
Jim,
yes, just email me your email address (to the address at the bottom of my posts) and I'll send you the file with the component stencil in it. If you want to wait a little while, I am doing a complete multi page file on the amp. There will be 5 pages. drilling mask, board layout, Chassis wiring layout, chassis drilling layout and face and rear plate layouts. Should be done as soon as I receive my mojo chassis.
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"One thing that amazes me is that people are worried about covering up the hole for the cap can.... Don't worry about it! Do what Doug did and use separate caps. You'll have better control over the grounding of each filter cap that way, and you can place them where it's convenient."
That's exactly why I covered up the hole in my PR build :)
Cheers,
Jerry.
Well holes and clamps are cheaper than cap boards and cap cans so we know why Fender did it. I'll be putting my filter caps on a board and in a can on the underside just cause I'm silly that way. ;D
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Unfortunately, no. The image, when uploaded to Photobucket, gets distorted and is fuzzy. The original file is not like that. Unfortunately, I tried to save to a different format, but got the same results. It looks like Photobucket automatically re-sizes it and that re-size makes it blurry. I've just uploaded it again, hoping for slightly better results. It seems a little better, but if you need me to, I'll e-mail the original file. The you can open it in Paint to zoom in on it.
HBP, have you tried gif. For some reason it cuts the blurries when I upload. Look how detailed my board in this thread is and it's under Doug's 100k limint with gif as well as fairly sharp. If you have a choice choose "source for both resloution questions.
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Well, the original file was a gif. Unfortunately, I don't ever do this stuff for other people to see (just use maybe hand-drawn sketches for myself), so the only way I had to make a layout was to take Hoffman's AB763 and cut/paste it in MS Paint to make the new layout. Paint is about a 1982 graphics program that Microsoft has seen fit to not throw away or update. What you see is the best I can get.
But it really is Photobucket's issue... The image is plenty sharp on my computer, but photobucket appears to resize it then add softening to the image to hide the resize, so it winds up smaller and blurry compared to my original. I don't know why they do that to this file and don't bother my real photos.
But the fact is that your layout looks better and is probably more helpful, as long as the underboard wires, tube pin connections and interconnections to the pots, etc are indicated.
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Please be aware that there was an incorrect value on the second power rail dropping resistor. I had it shown as 10k which is what it looks like on the Fender schematic but the Fender layout clearly shows it as 18K just like the third resistor. I have fixed it on the drawing.
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Barry,
No Problem. At home I'm using 2003. At work, where I have access to a plotter I'm using an older version. I'll have to speak with my IT team. I think the changed something on my system. I'm sure that I used to have 2003 on there.
Anyway, just wanted to say thanks. Man, you did an excellent job at these drawings. These are going to make this next build a "piece of cake."
I wasn't planning on using a master volume. Is there really any advantage? Also, I was considering one of the new Neodymium speakers (12") to keep the weight down. Have you heard anything about them? I still haven't had an opportunity to actually hear one in action.
Again,
Thanks for a great job on the drawings.
Jim
:)
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Barry,
No Problem. At home I'm using 2003. At work, where I have access to a plotter I'm using an older version. I'll have to speak with my IT team. I think the changed something on my system. I'm sure that I used to have 2003 on there.
Anyway, just wanted to say thanks. Man, you did an excellent job at these drawings. These are going to make this next build a "piece of cake."
I wasn't planning on using a master volume. Is there really any advantage? Also, I was considering one of the new Neodymium speakers (12") to keep the weight down. Have you heard anything about them? I still haven't had an opportunity to actually hear one in action.
Again,
Thanks for a great job on the drawings.
Jim
:)
Jim,
I'm building these amps for studio use. Anyway you look at it 12 to 15 watts is still loud for that purpose. As far as choosing between a master volume or an external attenuator each one has its own effect on the sound. With the attenuator you still get the power tube distortion although you have to boost the highs on the amp to compensate for the loss of that frequency range due to its use. That will probably be my final choice when recording but I thought I'd throw in a PPIMV for extra versatility. The reason I'm using a 1MA pot with a push/pull switch is so I can take the PPIMV completely out of the circuit if I desire which leaves the circuit stock.
By the way, on the stencils, the .022uf 630V cap in the small signal and coupling capacitors stencil was mistakenly labeled .0022. To change it just right click the stencil bar and choose edit stencil, then double click the item and it will open up in an editing window. You can take out the extra 0 there. After you do, click on the "X" of the editing window to close it and answer yes to the pop up for updating the item. When you put a stencil in editing mode you will see a red asterik on the title bar. When you've edited a stencil there will be a little floppy disk icon on the bar. Right click any stencil with that icon and choose "save" to make sure edits are saved. You can create your own objects and drag them into any stencil opened for editing this way. When you add a new item in a stencil it will be assigned a default name like "master 26". To give it a name that makes sense just right click on the item and rename it.
Here's one more tip; to have faceplates made by bnplasers print your Visio faceplate page to a PDF file and send that file to them. They use Corel Draw 12 to run the laser engravers and that program imports PDF nicely. This will save you the $25 set up fee for each plate. I just ordered two sets of the front and back plates in reverse etched black with white letters for $73 total. Jeanne at BNP is awesome to work with. If you don't want master volume just remove it from the Visio layout and give your amp name some more shoulder room. Do whatever you want with the faceplates. Just don't leave "Corona AmpWorks" ;)
Also, please be aware that I moved the on/off toggle and added a standby switch to the back panel of the mojo chassis. This leaves the original hole for the on/off toggle covered by the backplate and I'm drilling two new holes for the new locations. The old ground switch hole is also covered up with plate. The holes for the fuse, speakers, and the tremolo and reverb jacks are in their actual locations per the mojo chassis.
As far as the Neo speakers, I've not tried them. I won't be lugging the amp I keep anywhere as I don't gig so weight is not an issue for me. Tone is my only concern which is why I'm going with a 12" baffle board now for speaker versatility.
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Had an error on the layout, the intensity pot was labeled audio instead of linear. That is fixed now. Don't forget to refresh the page with your browser.
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OK Barry, that was one of my questions on the pots. The other question , which I put on my post is about the master (volume?) in the chassis picture with the board.
Thanks
BILL
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Ok Barry, I have another question . Looking at the Fender chassis layout, it appears that the reverb pedal jack is a shorting type and the other three with it on the back panel- vibrato, reverb input&output are open type jacks..is that correct? Also is the main speaker jack a shorting type? I usually see the extension speaker jack as a shorting type.
BILL
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Ok Barry, I have another question . Looking at the Fender chassis layout, it appears that the reverb pedal jack is a shorting type and the other three with it on the back panel- vibrato, reverb input&output are open type jacks..is that correct? Also is the main speaker jack a shorting type? I usually see the extension speaker jack as a shorting type.
BILL
Bill the 4 jacks grouped together (Reverb send, reverb return, reverb pedal, and tremolo or vibrato pedal) are RCA jacks not switchcraft jacks. They only have one conductor and the body is ground. The Reverb pedal and Reverb output jacks are wired together, with a wire then running to pin 2 of V3, and also a 220k resistor going to ground.
The main speaker jack on the Fender layout is a shorting type which shorts the OT secondary to ground if no speaker is plugged in. A 470 ohm 5 watt resistor in place of that jumper wire on the shorting jack would be a better safety.
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Ok again. Thanks again!!! So the reverb tank is plugged in externally into the RCA phono type jacks. I didn't look at my big Fender amp before I asked, and I see now that it has the same jack set-up.
Regards BILL
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Had an error on the layout, the intensity pot was labeled audio instead of linear. That is fixed now. Don't forget to refresh the page with your browser.
Barry,
I've started working on the circuit board layout to ensure that everything is going to fit. Please correct me if I'm wrong, but the .1uf and .047uf caps in the first stage seem very small (physical size that is).
In fact, I'm wondering if all the tubular caps shown on the drawing are too small.
I've purchased the Mallory caps and they appear to be bigger than the allotted size on the board. Is the turret spacing correct or do I have to adjust the spacing of the turrets to accomodate the larger cap bodies?
Jim
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I've purchased the Mallory caps and they appear to be bigger than the allotted size on the board. Is the turret spacing correct or do I have to adjust the spacing of the turrets to accomodate the larger cap bodies?
With a Hoffman board (using his drilling template), the turrets are 19/64th inch center-to-center (I just busted out the steel rule and big Hoffman aluminum drilling template to check). Measure and see what you turret spacing is.
On a Hoffman board, 400v Mallory 150's or 630v small-value 150's fit no problem. Orange drop or other polypropylene caps tend to be big, and usually have to sit high above the turrets so they can be allowed to crowd over other turrets. That's because they're physically very large by comparison.
I haven't tried printing out Barry's layout, because I have my drilling guide to use when laying out a turret board, so I can't tell you if the printed page comes out the right size (and that may even depend on your print setup options). All I can say is triple check (like you have), and if you need to, simply allow the caps to ride high so that they have room to sit over other turrets as needed to make them fit.
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Barry's layout came out OK for me, full size printed out. I checked spacing and it was right on. Those little yellow caps sure are small. I wasn't sure I had the right values when I first saw them. Doug's .1 mf caps fit the board just right in the positions listed for them.
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All of the dimensions of the components shown on the board were either taken from the Mouser catalog manufacturer's cut sheet or measured by me while I did the drawing. The turret spacing is completely accurate at 19/64 horzontially (not vertically as the vertical distances between rows varies) if you print the drawing without scaling (no fit to page). All of my layouts use the actual layout of Doug's drilling guide. There may be an errant component that is minutely off in size, but everything should fit.
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Ok, I did some digging in my parts stock and found some Mallory .1uf 630 volt caps that are longer then the turret spacing on the board. If that's what you bought, then I would suggest doing this with the leads"
Barry,
Thanks. Actually, I reworked your original layout. I used the cap stencil that includes Mallory 150s'. Everything looks fine now. Also I've been able to shorten the board about an inch with changing the .29" spacing the Doug uses.
I've used your suggested technique on my previous build with the Orange drops.
Thanks again for all of your help. I post some photos as I start working on this build.
Jim
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Ok, I did some digging in my parts stock and found some Mallory .1uf 630 volt caps that are longer then the turret spacing on the board. If that's what you bought, then I would suggest doing this with the leads"
Barry,
Thanks. Actually, I reworked your original layout. I used the cap stencil that includes Mallory 150s'. Everything looks fine now. Also I've been able to shorten the board about an inch with changing the .29" spacing the Doug uses.
I've used your suggested technique on my previous build with the Orange drops.
Thanks again for all of your help. I post some photos as I start working on this build.
Jim
Jim, you want to share the Visio drawing on the reworked layout?
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Does anyone on this forum have specifications for a Princeton Reverb cabinet?? I could buy one, but I would rather build it. (keeps me out of the bars) Not only that, I have more time than money in the winter, and all the tooling for woodwork. :)
Regards BILL
Oh yeah, I have my amp up and running, but dont understand how the little bias pot and selectable resistor are used to adjust bias. :-?
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Bill,
I would love to help you but I don't have any drawings of the cabinet for any Fender style amps. I've been looking for quite some time. On my last build ( Deluxe Reverb Clone) I used the basic dimesions shown on the Ampwares page.
If you do find some actual drawings, please let me know. I too, prefer to work from drawings then from some nebulous idea on how the cabinet is designed.
Jim
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If you can get the dimensions of a PR chassis and a picture of the amp you should be able to come very close. Just work out from the chassis. Of course if someone took a ruler to theirs it would be easier.
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yes, I have a Mojo chassis, like original. If the length , width and depth were available I would do it that way.
BILL
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According to the FFG, they are 20 x 16 1/4 x 9 1/2.
If you plan to use a 12 in there, you may want to make it taller, depending on how much clearance you have or want.
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Thanks for the responses guys :)
BILL
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Bill,
I have a raw finger jointed pine cab with a 12" baffle I had built by JD Newell. If you'd like I can do a drawing for you with photos.
Barry
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Thanks for the offer Barry. I just decided to buy one. I had a quote from a guy named Steve Watson last Dec, and just ordered it.
I really DO appreciate the offer. My Princeton reverb is running great, and it's the quietest amp I ever heard, Many thanks to you and Hot Blue Plates :)
Kind Regards BILL :)
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Thanks for the offer Barry. I just decided to buy one. I had a quote from a guy named Steve Watson last Dec, and just ordered it.
I really DO appreciate the offer. My Princeton reverb is running great, and it's the quietest amp I ever heard, Many thanks to you and Hot Blue Plates :)
Kind Regards BILL :)
I told you you'd beat me across the finish line. I'm Jealous. Isn't it sweet cranking up one's own baby? Hot Blue Plates is really the one to thank. He whipped that layout out of no where pretty darn fast. My Princeton is on hold thanks to the NAMM Vibroverb I built. I got several inquiries on it and now I've got more to build.
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Hi Barry Glad to hear the Vibroverb program is moving for you :)
BILLY
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I finished a 6L6 based princeton reverb using the fender layout a few months ago and have been playing it since. I am really not happy with the noise level of this amp. My deluxe reverb (using a hoffman style board) is really a much better amp. I am going to pull the princeton board and use the layout from this thread. Anybody tried 6L6s on this layout?
Great thread and THANKS.
Norm
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I finished a 6L6 based princeton reverb using the fender layout a few months ago and have been playing it since. I am really not happy with the noise level of this amp. My deluxe reverb (using a hoffman style board) is really a much better amp. I am going to pull the princeton board and use the layout from this thread. Anybody tried 6L6s on this layout?
Great thread and THANKS.
Norm
Hey Norm. Welcome aboard buddy. I've not used 6L6s on this layout but just finished a Vibroverb a couple of months ago with Doug's AB763 layout and the trem mods shown in the archive section in this thread:
http://76.162.4.197/Forum/yabb2/nph-YaBB.pl?num=1164566830
Of course it's got alot more power than the Princeton with it's small OT and PT but it is a really sweet amp with the 1X15" configuration. It's good to see you posting in here.
Barry
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I finished a 6L6 based princeton reverb using the fender layout a few months ago and have been playing it since. I am really not happy with the noise level of this amp. My deluxe reverb (using a hoffman style board) is really a much better amp. I am going to pull the princeton board and use the layout from this thread. Anybody tried 6L6s on this layout?
Great thread and THANKS.
Norm
Hey Norm. Welcome aboard buddy. I've not used 6L6s on this layout but just finished a Vibroverb a couple of months ago with Doug's AB763 layout and the trem mods shown in the archive section in this thread:
http://76.162.4.197/Forum/yabb2/nph-YaBB.pl?num=1164566830
Of course it's got alot more power than the Princeton with it's small OT and PT but it is a really sweet amp with the 1X15" configuration. It's good to see you posting in here.
Barry
Thanks!
I have a 180ma PT in my princeton and a vibrolux style OT. Still not as loud as my 6L6 deluxe though. The princeton fender layout has more noise than I expected. It is not as bad my bass players insanely expensive bass rig but much more than I expected.
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Has anyone out there besides Bill finished their Hoffman Princeton Reverb? I just about got mine done but I've been side tracked with the AC30's.
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Hopefully that project will make it into the Library. It was a really fun project and came out beautifully. :)
Those amps (originals) are going for BIG BUCKS on ebay, and I couldn't justify $1200 to $2200 for an original. Not only that, the modern clone may be better anyway!!
I had always wanted one, and I perked up when I saw the project on here from HBP and Barry.
Thanks once again Barry!! ;D
Oh yeah, I ordered the cab in January (!!) and it's gonna be here tomorrow on DHL :)
I've been running it thru other cabs.
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Has anyone out there besides Bill finished their Hoffman Princeton Reverb? I just about got mine done but I've been side tracked with the AC30's.
I am going to start mine this week. Did you end up using the capcan?
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I used a cap can, and ran the wiring along under the board. I was concerned about hum , but it turned out to be super quiet.
BILL
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I used a cap can, and ran the wiring along under the board. I was concerned about hum , but it turned out to be super quiet.
BILL
I will probably cut my board tomorrow. I only have the .1uf mallories so I will to adjust the layout some.
Norm
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Is anybody actually making these boards? I have been toying with the idea of putting a Princeton Reverb into a Blues Junior case, and this sounds like something that might fit. It would make for a wolf in sheep\s clothing, wouldn't it?
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Is anybody actually making these boards? I have been toying with the idea of putting a Princeton Reverb into a Blues Junior case, and this sounds like something that might fit. It would make for a wolf in sheep\s clothing, wouldn't it?
Well it would definitely be a different animal. I think everyone is just making their own boards. It's not that hard to do. You can get the board, turrets, buss wire and drill bit from Doug.
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OK blueslide guitar, I have a template for the PR board. If you send me the board I'll drill it for you. In fact, if you send the turrets ( I think there are 87 of them) I'll swage them in for you. You will just have postage costs, here and back.
BILL
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That sounds like a sweet deal to me! You are too kind! But what are the dimensions of the board? I'd like to measure my BJr. first. I assume you are referring to the standard blue board that Doug sells? This is really righteous of you man.
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No Blues, the board I'm talking about is the one on this post on page 1 that bnwitt and HBP layed out. Doug doesn't sell a Princeton Reverb board (or I would have bought one :))
Check it out and see what you think. The blank board is from Doug, 3.125 wide by 13.250 long. I believe the 3 1/8 (3.125) wide is the standard width that Doug sells, and you have to specify the length, with decimals, like the 13.250". Barry (bnwitt) also shows a shorter board. I don't have a template for that one. If I had the paper template for the short board I could use that to do a board for you also. I would just transfer it to another metal drilling template. Oh yeah, Dougs current board color is sort of tan. Look on his parts listing for board building parts.
Bill
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Check your email. While you're there look in your sent files folder. You may still have a copy in there.
...Steve
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Steve,
Thanks for the email, but I'm not talking about my drawings. I can still find those, no Alzheimer's yet ;D I'm talking about the actual chassis drawing. Someone did one that showed all of the chassis dimensions including the front slant angle etc. I used it to start my scaled wiring layout before I got the Mojo chassis for actual measurements and now I can't find it.
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Did anyone ever create an ExpressSCH file of the Hoffman style board layout?
If not, I guess HBP started with the Deluxe Reverb, so I could do the same. Guess I'm just lazy!
Cheers,
Chip
Chip,
As far as I can tell, the hoffman layout of the princeton reverb is schematically identical to the Fender version with the exception of:
1. the added 100 ohm artificial center tap resistors on the heater circuit
2. the added 470 ohm screen resistors on the power tubes
3. the added 1 ohm bias measuring resistors on the power tube cathodes
4. the addition of the 10K-L bias pot before the tremolo/vibrato intensity pot
5. 22uf 50Volt electrolytics instead of 25uf 25Volt caps on the triode cathodes and 22uf 450Volt caps instead of 20s on the filter caps.
I think that is it. HPB, speak up if I missed something.
With the exception of the electrolytic cap uf changes every change is a valuable one. The minimal value cap changes don't do anything one way or the other but raising the preamp cap voltage ratings is a good idea.
Barry
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Really cool little amp guys. :-)
Where does a person get a faceplate made for one of these Hoffman PR's?
thanks
Jim
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Jim,
If you don't want the master volume (most folks do not) you can get the cabinet, chassis and the plates from Mojo Musical supply. If you want custom face and rear plates, Jeanne at sales@bnplasers.com can do anything for you. They use corel draw, but any vector program (like Visio or Illustrator) can print to a PDF and she can import it for laser engraving.
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Jim - Marsh Amps makes faceplates that look remarkably vintage... They are also a re-seller for Mojo, so you can buy the chassis and cabinet there too.
Chip
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Hi again,
just want to make sure that the dimensions of the short board are 3.25 x 11.5, is that correct?
Thanks.
Jim
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I have eliminated all of the multiple posts with various graphics to minimize confusion. I will post the current drawings. Be aware that if you don't want a master volume, you just need to eliminate that pot and its wires.
the wiring layout
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The board.
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the loaded board
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The Chassis
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Hi again,
just want to make sure that the dimensions of the short board are 3.25 x 11.5, is that correct?
Thanks.
Jim
It's 31/8, so 3.125, not 3.25.
This is a great thread.
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Hi again,
just want to make sure that the dimensions of the short board are 3.25 x 11.5, is that correct?
Thanks.
Jim
It's 31/8, so 3.125, not 3.25.
This is a great thread.
Ah yes... thanks I mis-typed that and meant 3.125.
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I have eliminated all of the multiple posts with various graphics to minimize confusion. I will post the current drawings. Be aware that if you don't want a master volume, you just need to eliminate that pot and its wires.
the wiring layout
Are the three .1 uf 630V caps shown in brown on the right side of the board supposed to be a different kind of cap than the ones shown in yellow elsewhere on the board?
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The yellow ones all appear to be Mallory 150s, and one is a .1uf 630v.
Would this polyester film cap from Vishay be a reasonable choice for the "brown" ones Drew asked about? http://www.mouser.com/search/refine.aspx?Ntt=75-MKT1813410635
Newark Electronics only has 125, but they have Mallory 150s (polyester film) in .1uf 630v. Why spec something else for the blocking caps between the splitter and the power tubes?
Sorry if this is too much detail - I'm shopping!
Chip
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Please be aware that there have been comments regarding the Mallory 150s being to long for the vertical spacing on the board. I used Doug's xicons on my board and they fit perfectly. I believe Bill Creller used them as well. If you use the mallorys you will need to do a lead tuck on them to get them to fit or move the bottom turrets for them. Also, the mallorys in the preamp stage could be 250 volts instead of 630 volts and they would fit. Attached is a pic of my finished board with the Xicons.
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Nice looking board Barry ;)
Jim, I appreciate you saying that but I'm afraid it's not one of my best. I rushed that one to get the amp ready for a recording session. Still, it sounded great. ;)
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Yeah, Doug's xicon resistors are what he sez fit the Hoffman style boards. and are what I used. In fact I used them on most of the boards I did, like National clones.
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Since I am building not one, but two, of these beasties, some additional documentation will help me avoid/minimize mistakes. With that in mind, I have posted a schematic to reflect all of the work done by HotBluePlates, bnwitt, and others on the "Hoffman style" layout: http://www.el34world.com/Forum/yabb2/nph-YaBB.pl?num=1163460819/0 The bias adjustment pot threw me for a while and may not be correct yet.
Please note that our friend "Tubenit" created an accurate schematic of the original Fender schematic - I just changed a few things to reflect the "Hoffman style" layout updates.
It helps me a whole lot to have both the schematic and the layout in hand while soldering, marking both with a highlighter every time I add a component or connection.
Also, I'm attaching a parts list that I hope is complete (since I've already ordered almost all of this stuff). I can email an Excel version of the document if anyone wants one.
PLEASE let me know what corrections are needed either to the schematic or the bill of materials.
Many thanks to all of you for the work included in this thread. Hopefully this contribution will be helpful to others.
Chip
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Chip, the schematic looks good except for one little niggle... the reverb pot. It'll work as you have it drawn, but if you want your schematic to reflect the work that Leo, HBP, and bnwitt did, make this small change. Swap the leads on the reverb pot high side and wiper, like this...
...Steve
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Have any of you guys seen one of the reproduction Princeton Reverb chassis/faceplates/etc. packages sold by user "noojwut" on Ebay?
Are they any good? The guy is apparently in Thailand, and sells packages for several of the blackface amps, doling them out a few at a time. I did a search here and found one post by a guy who seemed reasonably happy with a Deluxe Reverb one he got.
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I've seen them on the website, and they look okay. You just need to make sure they fit whatever cabinet you plan to use. And naturally, if you use the fiberboard supplied, you can just use the original Fender layout.
That guy is a little interesting. "Item location" says Bangkok, Thailand, but the items look like stuff you could buy from Mojo or the like, and a search by his Ebay ID says he is in California.
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/me This post has gotten really long and hard to sift through for the diagrams. I added a condensed post here with just the diagrams.
http://www.el34world.com/Forum/index.php?topic=4770.0