Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on November 16, 2018, 12:02:37 pm
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OK, you all know my posts on the Plexi 6V6 amp from an AO43 chassis. I finally have the 6V6 Plexi sounding great (mostly stock, like Doug's and Sluckeys) all issues I had fixed. I have five more AO43 chassis's, looking for some advice on the layout of filters, choke, bd and utilizing this chassis to best meet the Hammond AO43 to a Plexi 6V6. I already have faceplates made for this head version so the pots are where they are. I plan on getting bd. material, turrets and switches, etc. and making a custom boards to fix.
I know several of you are familiar with the AO43, so here are the guts of an AO43, any advice on the placement of these components mentioned above would be appreciated.
I think I'd like to use two double 32mf cap cans in the place of the original ones, drilling the square holes round, should I run the rail R's on the bd or run wires from the caps to preamp tubes?
And that filter hole all the way to the right, should I just cover it or use it for one of the 23mf filters, too far away? I seem to run into problems kind of winging it, I don't have any programs to help in the layout and not up to date on their operation.
I have know several players that love the amp, so I'm making them for my friends and their friends.
So, before I order, any layout suggestions welcomed. I have the board already laid out except don't know if I should put the rail R's on the bd or run from caps. I will get most of what I need here from Doug.
EDIT: I have raised the laydown PT on standoffs to make room for the switches, on/off and standby.
al
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I would put the first and second droppers directly on the cap cans. Then put the third dropper and its filter cap on the board near the plate resistors for V1.
Or you could put all three droppers and the preamp filter cap on the board.
No real advantage either way.
I would also consider using Doug's OFF-STBY-ON switch rather than two separate toggle switches.
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Thanks, the boards I'm making has to be longer than the Hammond bd. in there now, so it it will cover the closest sq hole. Then I'll make the sq closest to the PT, round and then drill another round hole next to it for other 32/32 can. Take your advice putting the preamp 22uf single on the bd next near V1, run rail droppers on bd. I've already made faceplates for two switches, but would have been a good idea to use a single on/stby/off. Just want to make these 6V6s neater, it's time I start building something I'm proud of rather than a rats nest. :laugh:
Would you use eyelets or turrets? This amp has some 60 cycle hum, with single coils, guitar shielded, would upping the first filter to 40uf help with the hum? Using a 5AR4.
al
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eyelets or turrets
Turrets in my world win hands down, you have more options for adding/modifying. I think it's a "cleaner" look.
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The only thing with turrets is only two legs fit in the holes and thicker components legs can be a problem. I do like turrets better as they're hands down neater, I'll just use the holes for components and wrap wires around turrets. Thanks.
What could be the causes of this 60 cycle hum be? No hum with humbuckers, just strat with single coil positions, two and four hum gone. Does this with all my single coil strats. With nothing plugged in, snow noise comes when volumes are turned up past 7. Maybe the nature of the beast. Or would shield wire to volumes help, especially the master?
al
If it ain't broke, don't fix it.
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Just noticed these PT wires, gunk has leaked out, doesn't look like the wires are burnt but? Any thing I should do before I test this PT.
Maybe cover each wire with a piece of shrink wrap? Only on one side...?
al
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If it's a keeper, I'd pull the end-bell, shrink-wrap each wire.
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If it's a keeper, I'd pull the end-bell, shrink-wrap each wire.
OK, it tests good. Is this stuff just some of the coating that over time has heated and leaked? Nothing to be real concerned about as long as the wires are not bare or deteriorated. In the application I'm using these Hammond PT's, they never even get warm. Not all of them have this only two out of six and both on the same side, primary side. Am I being too anal, kind of scary to me.
EDIT: took bell off, looks like some gunk soften with mild heat, melted and flowed on covered wires a little, probably been this way right after it was made in the sixties. I'll carefully take some of the hardened tar-like gunk off and slide some heat shrink over wires as much as I can.
al
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I'd leave it as-is and not disturb it. I've seen the black gunk on old transformers caked on the leads coming out of the endbells, I believe it was put there for a reason, not anything that has leaked out due to heat. While it isn't pretty looking, as long as the cloth covering or inner jacket isn't falling apart, it's fine.
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I'd leave it as-is and not disturb it. I've seen the black gunk on old transformers caked on the leads coming out of the endbells, I believe it was put there for a reason, not anything that has leaked out due to heat.
Your probably right, but I fixed it anyway.
Al
Don't fix it if it ain't broke
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I built a Princeton (ish) Reverb with EL84 output in one of those chassis.
MV on the back, with switches for NFB (three position: Twin, Princeton, or none) and bias (cathode or fixed)
It was a tight fit with reverb and tremolo.
I did what you're talking about with drilling out the square holes to fit larger caps.
No Choke. Quiet and sounds great.
I put one of those filler plates in the far side large hole so it could hold a preamp tube.
I wasn't impressed with the stock output transformer and got a Classictone with 4/8/16 ohm outs.
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the boards I'm making has to be longer than the Hammond bd.
Dude, why is your board so long? Mine is only 6-7/8".
I built a Princeton (ish) Reverb with EL84 output in one of those chassis.
dmp, that's a nice conversion. Lotta stuff in that chassis, and all laid out very neatly.
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the boards I'm making has to be longer than the Hammond bd.
Dude, why is your board so long? Mine is only 6-7/8".
I built a Princeton (ish) Reverb with EL84 output in one of those chassis.
dmp, that's a nice conversion. Lotta stuff in that chassis, and all laid out very neatly.
The original Hammond board I used for prototype was 2" in width X 7 1/2", problem was the narrow width, no place for rail R's. Looking at dmp's board, it's a little longer and wider maybe 8 1/2" X 2 1/4" and still leaves room for the two square holes to be drill round for cans. Yeah, I don't need a bd any bigger than dmp's. Your bd was much wider, in my Plexi's I don't have room for dropping R's along the top or bottom, matter of fact nothing but a straight line of components. Not much room to get pots out once board is in without lifting bd., bad design. and the edge of bd is almost on top of tube sockets.
I'm not real good at designing a board, but my bds can't be wider than 2 1/4" and longer than 8 1/2" that's probably plenty to get everything in. I don't expect anyone to design a layout for me but I could use some help, I have five more chassis to build for friends so I want to make these Plexi's as neat as I can, almost all my work is conversions, I like utilizing chassis's from the ground up.
Also, I have to drill the 9 pin holes for 6V6's and wanted to move them a little further apart for 6L6's and EL34's, this would make these amps versatile as they are for gigging players. At this point, I'm figuring five bds at 2 1/4" x 8 1/2" with two cap cans in the original sq holes, if you look at the prototype below, the bd will be 1/4" wider and an inch longer more toward the preamp side. I also need to add a filter on the bd for the preamp, want to keep most of the rail R's on the bd. Get rid of tied single filters you see and the octals sockets closer to the chassis's edge. I move the PT up on stand-offs an inch so I can get the switches in.
Any suggestions, I'm all ears. EDIT: I took out that PPIMV, four caps on standoffs over PI.
Thanks,
al
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I'm not real good at designing a board, but my bds can't be wider than 2 1/4" and longer than 8 1/2" that's probably plenty to get everything in. I don't expect anyone to design a layout for me but I could use some help, I have five more chassis to build for friends so I want to make these Plexi's as neat as I can, almost all my work is conversions, I like utilizing chassis's from the ground up.
Get a piece of graph paper and cut out your board size . Then lay out the components - easy way to make the board as compact as possible. Once you have the turret locations marked, tape the graph paper onto the blank board and drill.