Where can I buy old capacitors?

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Thanks for reading,

I have an old Crown D-150 that's giving me some static down one channel and I've discerned that the trouble is with the old electrolytic capacitor on the circuit board. My problem has been finding the right match for the capacitors that I have. Thanks to crown I have all the schematics that I need (I feel like I could almost rebuild the darn thing from all the detail they give you), and it looks like I need:

25 mfd (micro)
15 V
NP (Non-ploar?)

I haven't been able to find exactly those specs and I'm slightly afraid to put a 16V or 23 mfd capacitor in there instead. Where can I buy an old capacitor, and am I being too paranoid?

Thanks for all your suggestions.
 
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Actually it would be an excellent idea to go through the amplifier and replace all of the electrolytic capacitors in it. They have a finite lifetime and if this amp is 20yrs old or more they are probably overdue.

Deterioration in performance will be gradual until a critical cap shorts and takes out a bunch of other parts.
 
I have one of those myself, bought new with matching preamp about 40 years ago.

As they said, higher voltage caps will be fine. And don't worry about the difference between 25 and 23uf caps All parts have a value tolerance, and hard to say what your original 25uf cap actually measured. 10% either way is expected.

And yes, NP means non-polar. SOme part makers call it BP for Bipolar. That is the same thing.

And Kevin is right about the life of caps. I haven;t fired mine up in a long time, I really ought to recap mine as well.
 
Thanks for reading,

I have an old Crown D-150 that's giving me some static down one channel and I've discerned that the trouble is with the old electrolytic capacitor on the circuit board. My problem has been finding the right match for the capacitors that I have. Thanks to crown I have all the schematics that I need (I feel like I could almost rebuild the darn thing from all the detail they give you), and it looks like I need:

25 mfd (micro)
15 V
NP (Non-ploar?)

The 25uF/15V is an input capacitor. They are rarely broken so are you sure that it is the problem?

If you lower the capacitance, your amp theoretically will not be able to produce the lowest frequencies as before, but the sound quality often will be better. Sometimes even if you lower the capacitance to 10uF you cannot hear the loss in the bass especially if your speaker is small (so cannot produce low frequencies anyway).

MKP type capacitor is better but the size is very big compared to electrolytic cap. But 10uF MKP is common and there is the cheap and the not big enough size.

The input cap needs to be a quality cap, MKP (too big unfortunately), NP or BP or simply axial capacitor, or you can parallel ordinary cap with 100n MKP (or higher). Other cheap trick is to use two ordinary caps back to back:

If you have two 47uF/6V caps you can connect plus with plus or minus with minus to create a 23.5uF/12V NP or BP (notice that the resulting capacitance is half the original). You can choose a wide variance of cap values here.
 
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Nichicon make bi - polar Audio caps.

Miniature Type Aluminum Electrolytic Capacitors

I would probably use the highest voltage parts you can find that will fit!

Personally I would choose the highest temperature rated parts - their service lives will be significantly extended. There has been a lot of discussion in professional publications about voltage rating vs temperature rating and life, largely if the capacitor is adequately derated voltage wise in a particular application there is almost no benefit to using a higher voltage part, the same however is not true of temperature rating. (Kemet, Vishay, Panasonic and others discuss many of these issues in their app notes. Note that using at <= 80% of voltage rating is considered good design practice.) Clearly since this is an audio application choosing capacitors known to perform well in this application would be sensible.

I doubt it is worth getting very tweaky in the selection process given the design being discussed, but sometimes good film bypasses on the main power supply capacitors can help.

You can often fit much higher values of power supply capacitance in the same volume occupied by the original capacitors, but should probably replace the rectifiers with something that can withstand the higher (sometimes horrific) surge currents that will result.

Silmics or Blackgates in a few key locations like the input coupling cap and perhaps dc blocking cap if present in the feedback loop are probably worth the slight additional cost.

Hopefully there are no tantalums in this amplifier, but if there are these should be replaced with low impedance AL types instead.
 
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The 25uF/15V is an input capacitor. They are rarely broken so are you sure that it is the problem?

I'm not sure that is the problem, I cleaned the input pots hoping that it was just a dirty contact, but that didn't help. So I'm trying to step down the line, starting with the easiest things to replace (don't have the money & time to rebuild the thing).

The reason I believe that it's the input cap is because after re-seating it on the board, the noise disappeared for awhile. It recently came back, and I think it's time to replace them. The static is a soft crackle similar to a sea-shore underneath any signal passing through the amp. If you have any suggestions on what it could be, I'm all ears.
 
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