Cap Replacement...Which caps to use

[Valvestate]

Hi,

I have revently been working on a broken marshall amp and am now considering replacing some of the caps on the board.

The amp is a Marshall and probably about 15 years old - maybe more. I was going to start with the two PSU smoothing caps and then move onto the high voltage pre amp filter caps.

I am looking at the Digikey website for caps and I am just taken aback at how many there are to choose from. I need two 2200uF 50V caps for the PSU smoothing however I am not sure how important a "direct replacement" is...Obviously I am looking for the same vaules and TYPE exactly but they seem to come in all manner of sizes and tolerances from different companies etc etc.

Where do I begin. Can I just choose something with the same value that is of a similar size etc and stick it in?

Many thanks for input!

[Chuck H]

The amp is a Marshall and probably about 15 years old - maybe more. I was going to start with the two PSU smoothing caps

If these are for the SS power supply it won't matter much.

and then move onto the high voltage pre amp filter caps.

You could hear a difference here. Probably not. Any low impedance, long life cap should be fine. In fact those criteria are just good practice, since your going to the trouble you may as well use a good quality part. I like Nichicon PW caps. I'm not sure if Nichicon makes an equal in axial lead if that's what you need.

Can I just choose something with the same value that is of a similar size etc and stick it in?

Yes. At least measure the board space where the cap will go so you won't end up with a part that's a little too big to fit.

Tube amps get warm so with aluminum electrolytic caps it's always good to choose at least an 85*C rated cap. Most are.

I'm guessing these are aluminum electrolytic type caps. If so, be sure to observe the correct polarity.

You may want to check out Mouser. Their on line catalog has a great search engine.

Chuck