Hoffman Style Board for a Princeton Reverb

[Imntgrumpy]

* EL34 - 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

[Imntgrumpy]

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

[waldner]

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.

[HotBluePlates]

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.

[Imntgrumpy]

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

[waldner]

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.

[HotBluePlates]

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

[EL34]

here's a couple pics of one I built.
You may be able to get a layout by looking at the pics.

[EL34]

BTW, I have that princeton reverb board and all the parts here.

I gutted my PR to make my Reverb stout.

[HotBluePlates]

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.

[billcreller]

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

[HotBluePlates]

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.

[billcreller]

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. :-/

[gehicks]

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.

[HotBluePlates]

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 to it.

[HotBluePlates]

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....

[Imntgrumpy]

HotBlue,

I've been looking over the drawing.  Where is the .02 cap shown below on your drawing?



Jim

[billcreller]

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

[bnwitt]

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.

[HotBluePlates]

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.

[bnwitt]

...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.

[Imntgrumpy]

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

[Imntgrumpy]

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

[billcreller]

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

[billcreller]

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

[gehicks]

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.

[HotBluePlates]

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.

[PRR]

> 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.

[bnwitt]

"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?

[phsyconoodler]

My princeton reverb board is 11-7/8" long.

[bnwitt]

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.

[phsyconoodler]

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.

[HotBluePlates]

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.

[Imntgrumpy]

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  :)

[bnwitt]

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

[Imntgrumpy]

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

[billcreller]

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

[HotBluePlates]

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.

[Imntgrumpy]

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

[HotBluePlates]

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.

[triode]

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.

[HotBluePlates]

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.

[Imntgrumpy]

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

[HotBluePlates]

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.

[gehicks]

"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.

[bnwitt]

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.

[bnwitt]

"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

[bnwitt]

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.

[HotBluePlates]

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.

[bnwitt]

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.