Help with location of filters, bd, sockets, etc

[dude]

Pictured is inside of a  Hammond AO-43 ungutted chassis which most of you are familiar with. Before I make mistakes on finishing a few of these chassis I have, can people experienced with this chassis and circuit I'm using, 6V6 plexi, give some suggestions on the inside layout of cap cans, iron, etc. 


The second pic is a completed 6V6 Plexi chassis, using the Hammond bd, I made some mistakes. First I can't get the pots out without lifting the bd. and it's too high due to the crazy Hammond turrets I used. I'll move it to the end and toward the middle to fix this and use a real 1/8" bd and reg turrets. I plan on drilling the square cap can holes round, to hold two cans, 50/50 and 32/32. I moved and drilled the El84 sockets too far inward, will keep closer to position of existing El84 holes just drilling the one more toward the PT, to give a little more space for 6V6's.


I've asked about this in a few posts but still unclear about making a mistake.


The caps tied to standoffs will be gone, PT is lifted 1" with standoffs as seen, all switches and pots same location as seen, I have face plates made so I can't change this.


I plan on using the same grounding system as seen, one star ground for PT, cans, bias, etc on the a PT bolt, the copper wire is grounded at the input only, not tied to main star ground. I'll have room for the choke outside chassis next to the cans (in middle), and OT, at 90* angle next to PT next to cans.


Any suggestions appreciated, I have one question: I usually ground the preamp filter cap to preamp side but since I'll have a 32/32 can, I can't (ground shared). Would one just ground that entire can to the preamp side or the main star ground? 


al   

[vampwizzard]

A lot to unpack in that post. Not sure what you're referring to when you say you made a mistake and you cant figure it out.

Layout wise on the hammond conversions I look for a working example of where other people have put tubes. Sluckey's amps were a major inspiration.

For the filter caps... many other amp designs ground the filter caps all to the power amp ground location on the chassis without issue. I did this on my spitfire inspired AO-39 conversion and it was DEAD quiet.

[sluckey]

Have you ever seen my website? Go there and look at my Plexi6V6. In particular, look at how I grounded my cap cans.

[Adrien]

Hey dude,

I've built a 6V6 plexi into a Hammond AO-29 chassis, so pretty similar to what you're doing.  It's a long, narrow chassis with not a lot of room for a board.

As far as your overall layout, it looks about as good as it's going to get with that chassis, pretty similar to how I did mine.  One thing I did that helped with the internal space issues was making a custom turret board instead of re-using the hammond cone board.  I still can't remove the pots on mine either fwiw.

I initially drew two board layouts, one for cap cans and one with the filter caps on the board.  See the link for my hand-drawn layouts.  I ended up using the layout with individual caps on the board.  It saves modifying the chassis, made the wiring easier and the ground scheme can be whatever you want.  The chassis was long enough to fit the extended length board, I think it may be in your case too. 

I used Doug's templates (cropped down to 8 rows) to draw the layouts, and I got him to make the board as well.  It ended up being 2.25" x 8.75" if I remember right.  The board without the caps would be about 5.75" long.  I just trimmed off the excess width from the board when I received it.  I did change the preamp filter caps to 22uF so they'd fit on the board better, but you could maybe put 33's on there too...?  It's an extremely tight layout due to the size constraints, had some "fun" soldering it all up but the amp worked great in the end.

Here's some photos of the finished amp and a link to the layout, hope this helps!

https://drive.google.com/open?id=1wMfDZ_gUzadn4W5-Zd02bP1AHyXlcKhi

[sluckey]

That's a good looking build in that tight space!

[dude]

Adrien and vampwizzard, thanks for reply’s. I realize my cap can question was premature as there are five filters in this amp, as seen on Sluckey’s site, a 22uf on the bd for last node grounded with preamp.                                         This build is tight and a challenge in the AO -43 but I always liked a good challenge and a small head cab. I think I have it down much better, especially after the seeing the mistakes in my first one. I need to keep the bd close to the bottom of chassis to be able to remove pots without lifting bd., it will be close to the sockets though. My biggest challenge is drawing up the layout from Doug’s links and software he posted, pretty good instructions but takes a while to get it down.                                                         I’m hoping to get Sluckey to say “nice built in a small chassis” but one has to earn his respect, l’m going to do my best to keep these builds clean and neat.                 al

[vampwizzard]

Like most things, the more you use the tools the more proficient you get. IDK if youll get the chance in our modern era but I watched a 20year veteran autocad drafter draw up some electrical panels by hand in 2d and the speed! no idea how he didnt eat through keyboards.

same thing goes for the layouts. youll learn more from trying and failing and then hopefully succeeding than you would from just building a part by part kit. Theres a special joy when someone comes up and asks what amp you were playing because it sounded really awesome and you get to say "oh.. just something I made".

[sluckey]

Hey dude. Anyone that can build a plexi in that narrow AO-43 chassis using that cone board has my respect and attention. Good job!   

[Adrien]

Thanks Sluckey!

Dude, I've tried using DIY layout creator too, and run out of patience.  That's why I just draw my board layouts by hand on doug's template, and then use his click-on-the-dots program to make the board and send him the info.  Then I just build the board off the layout and the rest of the amp using the schematic...no need for a complete layout diagram for every amp, I think.

So, just take the layout I posted a link to, and go here:  https://hoffmanamps.com/php/TurretBoard/CustomBoard.php

Then create a new file, and just click and create turrets where I've put mine in the drawing.  I add two extra rows on the end to leave room for mounting screws.  Doug can make a board using that info, no DIY Layout Creator required 

[Adrien]

I should add that the layout with filter caps on the board is verified, since I built an amp following it exactly.

The one without the filter caps I haven't checked thoroughly.  I would advise you to check it against the schematic if you decide to use it.  One small thing I noticed just now is that the junction of the bias caps and 1-ohm resistors should be grounded.  It's attached to the power section filter caps in the other layout.

These conversions are pretty challenging, I think you're doing a great job too.  I also have a tendency to cram way too much stuff into a small chassis since I prefer a small head cab.  Keep us posted, I'm looking forward to seeing the final product!

[dude]

Thanks for the encouragement guys, but remember the pic of the finished Plexi plays great, not that I can‘t get some ideas from your advice. Doug doesn’t make any boards less then 3 1/4” now, so no more custom widths from him. Although I probably could just order the bd at 3 1/4”, determine the turrets leaving the bottom empty and cut it when I get it. Though I already have the boards and plan to cut them to fit my final layout. I’m with you on hand drawn layouts, I’m a cabinetmaker by trade and did everything by hand, then the PC age came, I changed to programs that let my customers see 3D, much easier to land the job and very professional looking. I still do furniture by hand but kitchens are all PC software. So, for once I want to do a nice layout to fix an AO-43, maybe so others can copy it. Plus it’s a challenge I enjoy. I look at Sluckey’s stuff and i’m blown away, l don’t expect to get there but maybe closer than l am now. Yeah, I got that Hammond cone bd converted to a plexi and it wasn’t easy but now that I can see my mistakes, I want to finish the five chassis’s I have, as clean a build as I can get. When l’m done maybe I’ll deserve “good job”. Thanks again for all the info and layouts, much appreciated. All you guys have helped me from knowing nothing about amp building and repairing to a decent level that I can fix friends amps, at least most. Thanks again, al (aka the dude, ha) I got that name from my daughters as I went to a Halloween Party as The Big Laboski

[sluckey]

Dude, take a look at this short thread over at TAG. May be helpful to see what others are doing with AO-43s...

https://ampgarage.com/forum/viewtopic.php?f=9&t=32020&p=398322#p398322

[dude]

Nice Sluckey, thanks.  Never thought of a top plate for that clean look, I was going to basically do exactly what Volition did with cap holes and 6V6  sockets, OT and choke. My bd won't be as long but will be narrow like his. A thin piece of steel at Ace Hardware (big enough for two top plates) is less then $10, would solve the problem for using 6L6's and EL34s  and look very clean and professional. I did manage to get free software to make the face plates with help from a member here, they can be printed on heavy paper at any print shop very professional looking then cover in thin plexi glass from Home depot.


This face plate isn't the one I'm going to use but close, I changed the bold lettering and a few other things (posted the wrong face plate but you get ideal what that program can do.


Cheers, and thx again,
al