Cap swap

[FlyingZ]

With the exception of those marked in yellow do you see any problem replacing the caps with non-electrolytic?

Guild Thunderstar

[Enzo]

In the visible drawing you linked, as far as I can see, all the caps are already non-electrolytic except for two of the three yellow ones.

Caps are caps. 10uf is 10uf. You can use any type cap. But non-electrolytics will be a lot larger physically.

[FlyingZ]

That's what I thought, thanks. It's not a great schematic there are 7 E caps besides what's highlighted.

[Enzo]

On that picture?

[FlyingZ]

On that picture?

I think they only marked electros when necessary but not when they were merely the cheapest option. All the caps between bass and treble are polarized .0033, .033, and a bunch more. Some .001 caps are fish that's why I was wondering.

[R.G.]

I think they only marked electros when necessary but not when they were merely the cheapest option.

Why would you think that??????

Electro caps are what you do when you can't get enough uF in a small/cheap enough package to do anything else. They are inferior by most measures of goodness in capacitors, and a pro designer will only use them, as I said, where they can't get a non-electro with enough capacitance, smallness, or low price to work.

In general, if the cap is below 1uF, it's not electrolytic. There are exceptions, but they are rare, and rarer still in guitar amps.

All the caps between bass and treble are polarized .0033, .033, and a bunch more. Some .001 caps are fish that's why I was wondering.

I haven't seen inside the amp, of course, but I believe you are mistaken about them being electrolytic. There may be a polarity mark on the board, but I would bet a significant sum of money that if the amp is factory stock, none of those caps are electrolytic.

I've never *seen* a 0.001uF electro cap. You can get tantalums below 1uF, and aluminum below 1uF in quite-high voltages, but they are expensive and tend to be special order items. In general...

In any case, the caps in that fragment of schematic can easily be replaced by mylar/polyester film or other non-electrolytic type, and should be.

It is a good practice for reliability reasons to use non-electrolytics everywhere you can possibly stuff them in and afford them. Electros have a built-in wearout mechanism, non-electros don't. That's why "cap jobs" even exist.

[FlyingZ]

I could have sworn I saw a + on these... I should have known better.
Well thanks for the good info anyway

[Sweetfinger]

Maybe a foil side marker? Anyhoo, RG's advice is sound in just about any case- if you can stuff a non-electrolytic in, then do it. I also wouldn't change any of those caps unless they were leaking. It's kind of sad to see an old amp that probably just needed the electrolytics changed, but has had every foil cap changed to shiny new orange drops ...unless it is one of those Univox amps with those leaky gray PIO caps. That's the exception.

[FlyingZ]

I replaced all but 3 of the paper (I think) caps and it restored the missing high end.
Still have yet to resolve the low power issue. With a substantial boost it will produce its 40w otherwise it's more like 15w. The voltages are correct, tubes swapped except for the 7247, and connections retouched. I will ohm any remaining resistors today.
With a Klon or Real Tube boost it sounds fantastic, I can't stop playing it

[Guitarist]

Good to hear that it sounds amazing and that you're playing it! The "old cap in there" approach reminds me of meeting Larry Howard who insists his old amps not even get tubes changed. (He has a collection!!) The old dust covered tube stay put! They are what they are and if you tweak or modernize things you'll lose the olde tone. I'll always remember this. And have suffered amps to be "upgraded", but they don't always tone-up better.