Filter Caps replacement. Which is the best solution?

[jaysgr]

Hello,
I am quite new at the world of electronics and new at the forum too, and I would appreciate some help.
I have an old Fender Amp which has two Mallory 70uF/350V filter caps, which need replacement.
As I can't find anywhere capacitors with the same specs, I would like to know what is the best alternative.
68uF/350V ?
80uF/450V ?
100uf/350V ?

Also, should I search for a particular make?

Any answer would be much appreciated.
Thanks,
jay

[Justin Thomas]

Any of those would work fine; I personally prefer F&T, but only cuz they look cool in that shiny black plastic & gold lettering, and cost less than Spragues! I've not had any problems with any brand I've used. Get what you can afford & just make sure they're hooked up right - is it your amp or a customer's? Are you or they cash-poor? Those are my criteria... One caution - if they are going in the cap "doghouse," be sure they will fit - I got some Sprague 100/450s once and they were physically too big.

What amp? We like knowing what's floating around!

Justin

[Mick Bailey]

Welcome to the forum.

Electrolytic capacitors are not tight on tolerances - back in the day caps very often had a value of -20%/+80%. They also often drift in value as they age. A little either way doesn't matter much, though going too big can put an excessive strain on a tube rectifier (if fitted).

Nowadays tolerances are tighter. When you buy a cap its pretty close to the value printed on it. But remember the caps are going into an amp where the actual value was expected to vary a bit. The voltage rating is important, though - you don't want it to be lower, but higher is fine - even preferable.

Any of the caps would work OK, but 68uf and 80uf would be my first choice. In most amps 100uf would be fine, too.

F&T caps are available in 70uf/350v and are excellent quality. Nearly any branded cap of the correct voltage rating will work fine, though many suppliers are reducing stocks of axial leaded components.

[tedmich]

F&T does have a pleasant color combo, and are quite similar in performance to vintage caps, that said the lifespan of modern (usually radial snap-in) caps from japan is considerably better than F&T or JJ, as are most of their measurable specs including ripple current EFR leakage etc. Most of the "vintage feel" caps; multisection cans, twist on connectors, axial HV caps have little or no actual published specs. They are "rated" to 500VDC (or more) but almost nothing else is published about them. Luckily they perform much like the vintage caps they are designed to replace, look correct and don't cost more than 5 times comparable modern designs, as an example this Sprague Atom Axial
TVA1906 Vishay / Sprague | Mouser
20uF/500v +/-20%, 65C 1"x2" (huge!) and $17 each
vintage type caps are 'spensive, aesthetically correct and low tech, but usually sufficient

[gui_tarzan]

I know a lot of people like Mouser and I'm sure they're a good company, but they always seem to be quite a bit higher priced than other vendors I use.

Compare that cap above from Mouser at $17.11 for one:

Amplified Parts - $12.95
NewOldSounds - $10.90
Allied Electronics - $13.02
Newark Electronics - $10.25

I'm a frugal... no, CHEAP bastard and shop around for everything I get.

[Enzo]

It depends on what you are shopping for. I consider that cap a legacy of an older era, and places like Mouser sell it more as a convenience than anything. It is not the sort of part with a large market. I look elsewhere for amp-specific parts too. Look at Newark, they have only 12 in stock and when they are gone, that will be it, they won't stock them at all. Look down a bit and see that even if you buy 50 of them, what will then be the minimum, the price will still be $13.34 each, with a 13 week lead time. So clearly that is a clearance price. Some amp part companies may have bought bulk some time ago when cost was lower and are marking up from that instead of current pricing.

But Mouser and its competitors are not about a part like that. I buy resistors by the hundred there for a penny or two each. I buy power transistors, lower voltage caps and other commodity parts cheap. Plus they have relays, encoders, fuses, etc etc. I can usually get my entire parts needs there. I do buy my high voltage e-caps elsewhere, usually along with my tube order. I only consider Mouser e-caps up to 450v. The main drawback to intense price shopping is shipping. Each place adds $8-12 for shipping usually, so I can wipe out a couple dollars savings with an added shopping cost.

[gui_tarzan]

Oh I agree Enzo, shipping can cancel any savings you might find so you have to be careful. My only point was that there are other resources that a lot of people don't know about because they don't do the research. I have favorite vendors as well but I still shop around and always buy in some quantity unless it's something odd and expensive.

[Jam]

Beware if you buy parts on Ebay

[jaysgr]

Guys thank you all for your replies, it helped me a lot.
Justin, the amp is a silverface Scorpion Reverb 85-Amp and it is a friends of mine.

[trem]

I would be tempted to let price, and then size dictate my decision.
The 350 Volt caps MIGHT be a fair bit less expensive than those rated 100 Volts higher.
I have used A Lot of Xicon, Panasonic, and Nichicon caps in the last 5-10 years with no problems.
good luck