Chime in with some cap mounting ideas

[Matt300ZXT]

Since I'm going to have to "custom" mount some caps in this Red Bear amp, I'd like some of your opinions on how you would go about doing this.

I've considered getting JJ or F&T can style caps and some clamps and drilling a few holes in the chassis as my first option, but no sites seem to have either company's full line of these caps to pick from so I can see all my options and dimensions and get them from 1 place. Plus the diameters might be a bit of an issue in using the chassis' stock holes. I've also considered getting some turret board material and eyelets and some standoff legs and drilling holes in the chassis there and a few grommets and mounting axial lead caps on the board, then just run the appropriate wires through the stock holes in the chassis to keep everything clean and organized. Or there's also the option of mounting the board on the inside of the amp.

However, you guys might have some ideas I've never even thought of, so feel free to contribute what you think.

I'll post some measurements here:

Option 1: For mounting can style caps or a board with axial caps on the outside of the amp, the max height is 2 5/16ths, otherwise they'll hit the top of the box that mounts over the top of the caps to protect them. For usable room, keeping the chassis as original as possible with as few holes drilled, I have 3 1/16ths from front to back of amp, and 4 7/16ths from side to side to fit caps in. If I choose to use can style caps, I have 1 5/8ths spacing from the center of 1 hole to the center of the adjacent one, whether above it or beside it.

Option 2: For mounting a board with axial caps on the underside of the amp, where all the guts are, I have probably 5", maybe a little more, of space from side to side, and 3" max from front to back, probably a bit safer saying 2 3/4" to factor in room for leads, wires, and not bumping into the small board where the bias pot is.

I have seen where someone took axial lead caps and used some adhesive to stick them to the wall of the chassis but I think that's a little ghetto. I'd like to keep mine looking like a professional did it, and hopefully any option I use, I can mount the box over the top where the old caps went so it at least looks original.

Here are a couple pics to show the space on the outside of the amp, as well as on the inside.

[Stevem]

Well you have plenty of room for can type caps so I would get the needed size hole saw and have at it!
antique electronics has a good selection of JJ F&T , four section caps and others, have you checked them for what you need?

[Matt300ZXT]

Yeah, that's who I'm going with, under one of their many names; I'm using the Tubes and More one. Anyways, I had considered the multiple section can caps and having to just buy less of them but the 100uf ones were too tall to fit under the cap box. I've decided on buying some turret board, eyelets and standoffs and some JJ axial caps and putting the new board on the inside of the amp. There's a good bit of room in there for about a 6" or so long board to mount the 6 caps on, and I've got some 20 gauge cotton covered wire in my cart there so I can run new wires where I need to, as well as use it to wire up my new pots I'm buying as well.

I've got a host of new pots, wire, caps, tube sockets, as well as a handful of resistors in my cart there. I figure if I'm replacing all the sockets, might as well replace the resistors jumped across various socket pins while I'm at it just for the heck of it.

[xtian]

No need to drill big holes. There is so much room inside you can mount can caps on the walls. Also, radial caps are even smaller and cheaper and just as good and there are many clever ways to mount them.

[Matt300ZXT]

Well going back and checking it out, F&T makes 2" tall can caps (JJs are too tall), which will just fit under the metal box. Getting the dual section caps, I only have to buy 1 100/100uf 500v cap and clamp, and 2 50/50uf 500v cap and clamps. No matter which way I have to orientate them in the box, they'll fit underneath. I'd probably have to get a step bit and drill the holes slightly larger to clear the leads though.

Throw in some 18 gauge wire to replace a few wires that may not be long enough and voila, that should be another solution.

[Phil_S]

I don't think I'd be drilling holes for expensive can caps. It will be especially bad if you get it wrong. I wouldn't chance it.

I also don't think it's necessary to go for those spendy caps as they won't bring you any more value than far less expensive axial or radial singles.

Of course, it's your amp. You should do what you want with it.

Xtian makes an interesting point about using radial caps. He's posted some pictures of them in use. Search for them. Fat and short. They fit most anywhere.

I was thinking about a Fender style board for axial caps, but mounted inside. If you mount it outside, you'll need a dog house to cover it and that could run into some money that you don't need to spend. Fender did that because there was no room inside.

Since you have so much room inside (really, you do) you could strategically place a few terminal strips inside. You might get away with using existing holes. Hang the caps on the terminal strips. That might actually be the easiest and most practical. Probably the cheapest, too.

Why do you want to replace all that other stuff? Is there something wrong with it? If you are going to all that trouble, you could just build a different amp in that chassis...the amp of your dreams! If there is no compelling reason, leave all that other stuff alone. In particular, if you lack the experience, you may do things that will give a bad result without realizing you are doing it. I'd advocate for a minimalist approach. Do the caps first and then see if it needs more work.

Finally, remember that it is likely you see a pair of 100u 450V caps in series because the maker couldn't source the 600V rated caps you need for a circuit that delivers ~500V to the plates. In series, you have a 900V rating. (Or they couldn't be sourced cheap enough.) You don't need to do all those totem pole caps. You can buy a single 47u or 50u 600V rated cap and it will do what you need. With less caps, your job is much easier and you eliminate the balancing resistors, too. (Though you still may want to keep a bleed resistor in there across the first cap.) This comment applies to whatever caps you decide to buy.

If anyone thinks I'm wrong about ditching the totem poles for single caps, please speak up!

[Matt300ZXT]

It turned from a simple pot replacing job into a pot, filter cap and socket job. The sockets have always been extremely loose and tightening methods didn't really do anything for it. The pots in these things are plastic bodied crap, so since 1 was bad and killing it, might as well replace all 6, and might as well replace all the filter caps too.

If I'm tearing into something, I'm just going to replace all the maintenance/basic wear items, whether it's an amp or one of my cars.

As far as cheap radial caps, I've seen the Nichicons, Illinois, etc go for much cheaper than the JJ or F&T, but I just don't know about putting such cheap caps in my amp when nicer ones aren't really all that expensive.

[Phil_S]

Low cost does not equal cheap. This is a classic case of market economics at work. These radial caps are widely used so the manufacturers make them by the pallet full. High quantity production brings down unit cost, brings it way down. I believe this explains why the same maker's radial cap is so much less than the equivalent axial cap.

Nichicon makes a good cap. So does IC. It is likely both of those brands are far better quality than the original parts. I don't understand the hesitation.

Save some money. Take your honey out for dinner with what you save. Or buy yourself some new tools. Whatever.

What is the measurement of the attached area? I am guessing 4" x 8". I am thinking you have lots and lots of room to put a 3" wide board in there. AES sells a generic board fitted with 60 turrets for about $10. You could load it up and then mount it. It would save you a ton of work and it would give you a great result.

[TUBEDUDE]

Is there enough room to hollow out the original caps and slide in some F&T's, or similar?

[Matt300ZXT]

The usable room in the old cap area is about 6-7" by 2.75" max. Anymore than that and wires/leads will be up against the chassis or the power amp board. The radial caps I like are only 1.66" so that leaves plenty of room for wire/leads to be set up comfortably.

I looked at the refurbishing of the original caps but it didn't really do anything for me. Too much work and my luck it'd probably come out looking crappy so I decided against it.

[Structo]

Although I haven't experienced it, some say the multi value caps are noiser than discrete caps.

Caps are so much smaller these days it should be easy to fit them.