Trying to Match a Hammond PR-40 PT to a Twin Project;>/(Hot Shot 48 Plexi)

[sluckey]

haven't you got the diode facing the wrong way?

The bias diode is drawn correctly in that latest layout pic.

[Platefire]

Yeah, guess 100uF is kind of overkill Guess I was looking at size more than value.

I did go through my inventory. Found some NOS Tantalex 13/150 and some Radio Shack 22/50's.So out of that I guess the 13/150 is the best fit. I've even got one 50watt Marshall 1987 schematic that even shows 8uF. Thanks for all you recommendations/improvements that got incorporated into the layout. Platefire

[mresistor]

looking pretty awesome ...   

[Platefire]

Thanks mresistor

Kind of rag tagging existing parts together to make a project. Without all Dummyload and sluckey's help, it would have never even got off the ground. I've been having these Hammond PR-40 parts for years and thought they were useless to me. I will try to make it nice as possible.
Haven't decided rather I will leave it as an exposed chassis with all the tubes hanging out or enclose it in a head cab. It's going to be a little top heavy with the big transformers top mounted---a cab with a well placed handle of handles might help that. I kind of think of it as a hot rod amp, so maybe it would be better leaving everything exposed except a bottom plate to cover the circuit and to mount feet on. Something to ponder on in 2016. Platefire

BTW-Here is the latest rendition of the Layout. Thinking of calling it "Plexi 48 Hot Shot"---referring to a plexi with hot switch.

[Willabe]

You could lose 1 more turret. Put the .1 cap on a 45 degree angle up to the 10K R and bring the 100K R to that junction too. and move the turret to the right at the bottom of the 100K R. Don't forget to move the jumper wire up to the 10K/100K/.1 junction. 

[Platefire]

Willabe

With all the recommendations to rearrange to save turret lugs, I went back and checked the current price thinking they must of severely went up in price (15 cents each). With your recommendation I can see where I could also re-arrange the mounting of the .022 cap above that location and shift all the components east of that location, further west another 3/8" spacing forward therefore reducing the length of the board to 11 5/8" long.

However I might wait for any more recommendations to come in before I shift any more components
so I can do it it one final sweep. In other words, I've got the "layout correction Blues"  Thanks, Platefire

[sluckey]

My layout designs usually go through several minor revisions until I'm satisfied. I don't rush this phase.

[Platefire]

Yeah, I need to take it easy. I'm my own worst driver! Relax and enjoy the ride. Take time to get it right.  Platefire

[Platefire]

Revised Layout again. Willabe's suggestions have been incorporated. The board in now 3/8" shorter from 12" to 11 5/8" long. It should be getting close to being all it can be

Also got attached OT from ClassicTone coming. Platefire

[Platefire]

Got the OT in today. This looks like the way I need to position the transformers/choke. If you see any problems, let me know. The rectifier is 1" from PT. Platefire

[mresistor]

I positioned my transformers on my Single-ChanDR very similarly and the PT is also very close to the rectifier and haven't had a problem at all. Also it should be noted that on many of the old Hammond PS chassis the PT is in very close proximity to it's valve rectifier and they work fine.
 

[Platefire]

Thanks mresistor

I also have a Pignose G40V and everything is really crammed up in close proximity, and it seems to work OK. I pretty bad about missing stuff, so it's nice to have someone look over your shoulder. Thanks, Platefire

[DummyLoad]

my thoughts: the choke is carrying power load of the amp. it it will have stronger flux lines, so suggest rotating choke and OT 90 deg. my concerns likely unwarranted so take with a grain of salt, so to speak. just thinking out loud...

--pete

[Platefire]

DL, I thought the choke needed to be 90 degrees out from the PT. If I rotate the choke and OT 90 like you said, that would put the bells all facing the same direction. Is that what you was talking about??

Now if I rotated just the OT 90 degrees from it's present position, that would put all three 90 degrees out from each other. Which one? just checking Thanks, Platefire

[DummyLoad]

If I rotate the choke and OT 90 like you said, that would put the bells all facing the same direction....

yes.


--pete

[Platefire]

OK, Like this!

[DummyLoad]

OK, Like this!

yessir, that's what i was thinking.


--pete

[Platefire]

Looks like a bunch of soldiers standing at attention to me

[DummyLoad]

i built this on the dual SE marshall breadboard. lost interest and was about to tear it down, so i grafted in the hammond PS and one of doug's 50W 4K:2/4/8  bassman OT - p/n 018343. sounds really nice - couldn't kick in the pants as it was late. a friend came over to play it and likes it's clean tone. it's fairly loud as well.

with SSR, B+ surges to 540V for about 5-6 seconds at turn on & don't care: these are JJ caps for experimenting on the breadboard. if i were to build it, i'd use MIEC 47uF 600V caps.

schematic with telemetry attached.

--pete

[Platefire]

Interesting! Two chokes? that's a new one on me. So on the clean setting that you was liking, what was your two volumes set at?

I've never installed a relay before but I think I might look into that for the possibility/difficulty to make my hot Switch, foot switchable. Not sure just a consideration. May aught to build it with just a DPDT first to see if I like it first. On the one amp I now have with a hot switch, I tend leave the hot switch on all the time and set the volumes so i can go from clean to sting with my guitar volume. Platefire 

[DummyLoad]

single coils on strat. preamp at about 1/4 - master at about 1/2.  if you run PS with SSR use 600V electrolytics.

http://www.studioelectronics.biz/sunshop/index.php?l=product_detail&p=1587

--pete

[Platefire]

Sooooo-------if I use SSR and 600V caps, that means I can have a standby switch, right? Platefire

[DummyLoad]

ju don need no steenking standbai. 

in theory, yes.

--pete

[Platefire]

DL, since you shed new light on how the the Hammond PT/Choke/SSR behaves with the 2204, I decided to do my version of my layout with SSR. Please check um out!!  Thanks, Platefire

[DummyLoad]

flip the 220K grid leak resistors for the power tubes and save a turret and some wire.

what you've laid out will work, however, i'd like propose a couple of suggestions:

a) if you flip the preamp power supply caps (C, D, & E) you could run the power rails on the tube side of the turret board. that keeps power away from the pots and ground rail mixed with the signal lines. if you flip the anode resistors orientation, that would help in that respect. also, you'd run the power leads under the turret board.

b) the bias supply has high volt AC supply mixed in with DC runs, suggest that it be moved to the end of the board - closest to the A & B supply rails and share the same ground. run the output of the bias supply along the ground side of the board or under the board to the grid leak resistors of the power tubes.

thoughts? other ideas? comments?

--pete

[Platefire]

Thanks! Think I will think about this a while. Platefire

[Platefire]

Hay I'm back! I agree with all the suggestions you made, just had to take a short break and refresh

I am working on a new plan and will post it soon as it's done. Thanks, Platefire

[Platefire]

DL, this is my rendition of what I think you recommended do. Check it out and see if I'm even in the Ball Park  Thanks, Platefire

[Willabe]

I just noticed that the PI B+ and coupling caps on the eyelet board are wrong. 

Coupling caps are being fed after the PI plate R's. So the AC signal from the PI that goes to the power tubes has to go through the PI plate R's.

[DummyLoad]

what willabe said + the bias feed is AC not DC as there is only positive there. you need need the negative half of the sine there.


please see attached for clarification. :-)


--pete

[Platefire]

Yep, I did the same thing on the V1 plates/caps too.  Think I will re-title this amp "Twilight Zone". I can tell it's still pretty poor layout looking at you guys boards but here is the corrected copy. Maybe in all it's poorness it will still work. Thanks for your great tolerant patient inspections! Platefire

BTW--I thing scooting the board further east about 1" toward the PT will also help the hookup runs.

[Willabe]

BTW--I thing scooting the board further east about 1" toward the PT will also help the hookup runs.

Yep, agree. 

Besides you don't want the west end of the board touching the west end of the chassis.

[sluckey]

BTW--I thing scooting the board further east about 1" toward the PT will also help the hookup runs.

Ah, the beauty of Visio and full scale components! There's no guessing if it will fit or how the wiring will look. It should look just like the drawing.

Not saying you must go out and buy Visio for just one layout. But if you have Visio and are not using it, you are missing a lot.

[Platefire]

I didn't know what Visio is, so I did a google search on it. I definitely don't have it already. I really do miss a good drawing program because in my job I had the best with every tool you could imagine to accomplish what ever you needed. In ExpressPCB/Sch you really have to be creative to accomplish what you need. So I'm assuming you have Visio? Platefire


BTW-I'm looking at a CAD Clone free download "Draftsight". Would like something I could do
electrical, architectural and mechanical with.
http://www.3ds.com/products-services/draftsight-cad-software/free-download/
 

[DummyLoad]

curious as to what are the chassis and board dimensions are? the big E-caps don't seem to be to scale.


--pete

[DummyLoad]

I didn't know what Visio is, so I did a google search on it. I definitely don't have it already. I really do miss a good drawing program because in my job I had the best with every tool you could imagine to accomplish what ever you needed. In ExpressPCB/Sch you really have to be creative to accomplish what you need. So I'm assuming you have Visio? Platefire


BTW-I'm looking at a CAD Clone free download "Draftsight". Would like something I could do
electrical, architectural and mechanical with.
http://www.3ds.com/products-services/draftsight-cad-software/free-download/

draftsight works and is better than what you have now. it's not as versatile as visio, but far better than express sch for layouts.
you should be able to buy visio 2010 download + activation key for under $200. be careful buying SW off ebay.


--pete

[Platefire]

Well on ExpressPCB, I have it set to inches and not mm. So each square grid is a square 1/10 th of an inch. So those 50/600 E caps are 11/16"(.6875)x 1 7/8"(1.875). 1/16"=.0625 and 1/10th of an inch divided by .0625=1.6 sixteenths in every .1(1/10") cube or .8 Eight inch in every cube.

So 11/16"divided 1.6 Sixteenth per block= 6.75 Blocks in diameter.
and 1 7/8" long divided by .8 Eighth inch per block=18.75 Blocks in length.

That's is how I scaled it and when I drew it I thought it too large also, but when I checked my dimensions or blocks, it was correct and when you compare it to the 3 1/4" board it does look proportional to that.

If you find any flaws in my measuring techniques, let me know. The outside dimensions of the chassis is 8 1/4" x 22"(8 1/8"x21" inside). The board is 13 7/8" long. The end plates of the chassis that the handles go through is 1/2" aluminum---weird/heavy! Platefire

BTW--also the X(horizontal) and Y(vertical) Grid coordinates help located everything from point of beginning, upper left hand corner of turret board.

[Paul1453]

ju don need no steenking standbai. 

--pete

I used to think that a standby switch was important for tube amps.  I mean most of them have one, right?
We need to warm them tubes up before throwing them into action, I've heard people say.   

Then I spent the time to read the PS section on Merlin's website.  Major eye opener.   

Now it seems to me the downsides of using a standby switch far outweighs the positives.
With a tube rectifier our B+ gradually climbs to operating voltage as the tube warms up.

The biggest drawback is one I had never heard about before.  Decreased tube life.
Heating the tubes without voltage applied for extended periods creates a chemical reaction and a film to build up on the elements.
Once that film develops there is no way to remove it.  Leading to a significantly shorter useable tube life.
I want my expensive tubes to live long and prosper.  \\//   

[Platefire]

I wonder about Marshall 2204 style standby?? they cut PT secondary ACV Reds to rectifier and allow the heater ACV to keep the heaters going. never tried that method before! 

I hadn't planned to put one in this one, but thanks for reminding me.  Platefire 

[Willabe]

Well on ExpressPCB, I have it set to inches and not mm. So each square grid is a square 1/10 th of an inch. So those 50/600 E caps are 11/16"(.6875)x 1 7/8"(1.875). 1/16"=.0625 and 1/10th of an inch divided by .0625=1.6 sixteenths in every .1(1/10") cube or .8 Eight inch in every cube.

So 11/16"divided 1.6 Sixteenth per block= 6.75 Blocks in diameter.
and 1 7/8" long divided by .8 Eighth inch per block=18.75 Blocks in length.

I think your making it much harder than it needs to be. 

I set the 'Display grid' at .0625 (1/16") and the 'snap to grid' to .03125 (1/32"). So I can snap a line or part in between the 1/16" grid.

I measure every part I use and make it to scale, then name/store it. So everything is to scale in my drawings.

This way I can print out any templets I need to make an eyelet/turret board or for a transformer placement/drilling templet.

I also make little rulers that are a single line with cross hatch marks on the 1/4" and are numbered on the 1" mark. I save these and put them on the drawing I'm working on when needed.

To be able to save them as a part you have to put a dot on it or it wont save. And you can flip them/rotate them left/right and up/down, so you only need to make 1 of each length.     

[Paul1453]

I wonder about Marshall 2204 style standby?? they cut PT secondary ACV Reds to rectifier and allow the heater ACV to keep the heaters going. never tried that method before! 

I hadn't planned to put one in this one, but thanks for reminding me.  Platefire

Still heating your expensive tubes = chemical reaction = premature tube death.   

[Platefire]

Willabe

First of all, this is the first layout drawing I've tried since I retired and had to give up all my expensive drafting equipment. Second I made a big mistake when I started in ExpressPCB instead of ExpressSch---because I didn't find out until I tired to post it, Doug's forum don't support ExpressPCB files, only Sch files. So I won't try that again in PCB

But Man Thanks! for the tips on setting the grid. I tired it and works great. You layout drawing looks fine. Drawing and saving parts also sounds good, because once you draw them to scale, you can use them from now on. Your right, I was making it harder than it needs to be.

Also I'm interested in what you said about printing out board templates. Like how do you print them out full scale? and also if board is longer than 11"(8 1/2 x 11 sheet), how would you print it out like mine 13 7/8"? Platefire

[Willabe]

Also I'm interested in what you said about printing out board templates. Like how do you print them out full scale? and also if board is longer than 11"(8 1/2 x 11 sheet), how would you print it out like mine 13 7/8"?

You can use legal size for up to 8 1/2" x 14". But if it's longer than that then;

You have to make a 2nd drawing of just the board, print it, cut the 2 parts of the board out and then tape them together, but it works fine. Just a little more work.

Once the drawing is finished, you highlight the full eyelet/turret board, then copy, then past it on a new sheet. Size the new sheet to what ever size paper your going to print on, 8 1/2" x 11" or 8 1/2" x 14". Print full size/full scale. 

Then you find a place where you want to break it in two. I run a line from top to bottom where I want to break it and put 3 small lines going left to right across so I can line them up after it's printed and the 2 pieces cut out.

Play with it a few times and you'll get it right. 

[DummyLoad]

was thinking something like the attached. probably would be better if the B+ nodes D & E caps were centered between the V1 & V2 components: it's late and that's about it for me tonight.

i have the visio file for this layout and IF you like it, then perhaps doug might be willing to fab the board for you on his CNC? couldn't hurt to ask unless he has a huge cyber club.

--pete

[Platefire]

Wow! That is pretty amazing. I ran some hard copies so I could study it awhile. Thanks, Platefire

[DummyLoad]

latest rev: rev2. i like this one mo bettah.

i included patterns for boards with 1/8" eyelets and hoffman 3/32" turrets.

--pete

[Platefire]

     Well all I can say is that is about an efficient board design for this particular amp situation as you can get. That's got to be it! I'm really impressed with Visio too, it looks like the real thing in every detail. I personally like turrets over eyelets but you got both covered. I assuming you could also do a dandy chassis layout with Visio too. Thanks for all the hard work to put that together. I'm learning a lot about board layout. I thought I knew a little, but I might be mistaken(as Billy G once said)! It really is an art to include all the best electrical practices and symmetry. It looks like you got that pretty well nailed.

What it Doug's CNC---computer Bla Bla? I usually enjoy making my own boards, but if it wasn't an arm and leg, might be alright!

Got a question on a couple of value caps on revision 2. On V1 cathode cap you have a 25uf instead of a .68 and also to V3 -2 you have .0022 and instead of .022. Don't know if your recommending a change or it's a mistake?

Thanks much! This thing is going in the right direction. Platefire

[DummyLoad]

Got a question on a couple of value caps on revision 2. On V1 cathode cap you have a 25uf instead of a .68 and also to V3 -2 you have .0022 and instead of .022. Don't know if your recommending a change or it's a mistake?

Thanks much! This thing is going in the right direction. Platefire

glad you like it: i'll fix those errors shortly. you can create the wiring diagram and any assembly diagrams in visio - several folks here and self do as well.

i created this amp completely in visio: it went from a concept experimenting with pentodes to a working model.

--pete


EDIT: corrections  attached. please review and check wiring.     

[Platefire]

Thanks! Believe it or not, I'm not sleeping! I'm going over the final board layout and am accumulating a few questions that might not amount to a hill of beans but maybe need to be ask before we proclaim this the final plan. Maybe some of it due to my unfamiliarity with Marshall. When I get it all together, I'll post. Platefire

[Platefire]

Ok, here goes so this may be long. My only experience with a Marshall was a 80's Plexi that I repaired. So my concentration was mostly the repair, but I do recall liking it, what little I played on it. So Marshalls are a blank canvis with me but I know the original sprang from a 5F6A Bassman and developed from there. So I can see a lot of 5F6A in this amp. So I see some of the major differences is in the preamp, power tubes and seems more filtering of power rail. So my desire on this project is to sample the Marshall animal a little bit. So some of my thoughts on the amp may be based on assumptions and not fact. So I would like to be sure I'm truly understanding what I'm building.

So I had to select a 50 watt(48) circuit for this project so the 50Watt Master Volume 2204 was what I selected(schematic attached). My thought was to have a low gain channel for mostly cleaner stuff and have the hot switch to bring in the other gain stage to make it really distort or either leave the hot switch on all the time with the MV turned down and preamp Vol up and just use my guitar volume to go from clean to crunch. So my major change to the 2204 circuit was to do away with one channel and bring the other gain stage in with Doug's hot switch as needed. So based on all this assumption, this is my questions:

1-Inputs & Channels on the attached stock 2204.

a- I assume the "low" and "high" inputs/channels on this amp are for low & high gain?? but not sure. I know on vintage Fenders the high was like for single coils and low for humbuckers because clean was the goal and they sure didn't want their amps to distort. I know Marshalls where trying attain more gain---so their intention for low & high may be completely different. So the low input has a cathode 820R/330cap and the high has a cathode 2.7K/.68 cap on attached example. My amp inital clean channel has a cathode 2.2K/.68cap which is more in line with the "High" channel. I see on Doug's hot switch schematic, he has the cathode 2.2K/.68 as the inital Plexi channel. I think seeing Doug's V1a cathode set up is why I used it on mine! This is a little confusing to me. Would those values be right for what I'm trying to do?

b-The output of the plates on V1 has a .002 coupling cap on the high channel and .02 on the low channel. I've got the .02 on mine with the high channel style cathode set up. So I know the higher value is less bright---so I think that the .02 would be better because I really don't want a overly  bright sound or am I tracken right?

c-I also see the 100K resistors after the coupling caps. I am assuming that these are to help separate the signals of each channel going into the volume pot and since I only have one channel is not required for mine??? Anyway I don't have the two 100K's in my amp and haven't tried to include them because of the previous reasoning. Is my reasoning good?

2-Tone Stack:

a-Just wondering? On your board layout you have the second .022 labeled to bass 2 term. Since the bass 2 term connects to treble 3 term, couldn't you just run that one you got labeled bass 2 to treble 3 since there will be a wire run from Treble 2 to Bass 2??? That would be a shorter run if legal:>)

b-On the bass pot on the attached 2204 schematic there is an arrow through it, which I never knew exactly what that means? So on my schematic you made a correction where you disconnected Treble 3 connection to Bass 1 connection and connected Treble 3 to Bass 2 and left a no/connection on Bass 1. So is that what that arrow through pot means--the correction you made?

I have checked your layout and everything looks good to me. If any of the questions I ask don't cause any major repercussions, we should be good to go. Thanks Much! Platefire