[earplay]

Insert standard newbie qualifier here.   

I've got a 20 years old tube amp. Should I replace the big electrolytic caps due to age?

[S Clark]

Not necessarily.  Can you test them to see if they are still at their stated value?

[avahifi]

"Should I replace electrolytic capacitors due to age".

How old are you?  If you are over 80 or so then your hearing is probably so far gone it won't make any difference.

Frank

P.S.  Seriously, electrolytic capacitors do age and become resistive, especially ones made years ago.  I suspect your 20 year old capacitors in signal path applications are getting in the way of high frequency range and transparency by now.  Be careful when you replace them, use non-polar units when you can, and better yet film types if you can find the value and voltage rating in a rational size (they are generally much larger for a given capacitance and voltage than electrolytics).  If you must use polarized electrolytics, make sure they are installed with the correct polarity and never use them in a circuit where the AC audio signal could exceed their bias voltage. They break down and distort badly (or just blow up) when they see a reverse voltage.

[earplay]

Thanks,

Well, I could, if I knew what I was doing. I have a Rat Shack voltage meter, but I don't know how to apply it in this situation. In fact, I don't know if it is applicable.

I was wondering if mere age would cause them to deteriorate (I know it causes me to deteriorate). If the answer is maybe, then I should test them.

[earplay]

Thanks Frank,


I really appreciate your info regarding using different cap types.

These are power supply caps. They stick up in plain sight along with the tubes and transformers. Their value is 1100 uf/ 450 vdc. Actually, it says 450 wvdc.

Caps with this value are available, but I don't know if they will fit the hole and bracket that are used in their mounting. I might have to fudge that, but I'm wondering if and how much I can fudge on the values. Any ideas?

[mgalusha]

Unless you are certain of the operating voltages of the gear, don't fudge on the values. There is almost certainly a good reason the designer used 450 volt caps. Given the high voltages in tube gear, if you are unsure at all about what you are doing I suggest finding someone knowledgeable in your area to give you a hand or locate a good guitar amp tech in your area. Those guys fix tube amps every day and almost certainly could replace the caps if need be.

[earplay]

Thanks everyone,

No, I don't know what I'm doing. A guitar amp guy is close by. In fact, there are several.

This board is great! Not least, by exposing my ignorance.