Smoothing caps

[cr0wl3y]

Hi there,

Was wondering if I could get some advice on what to use to replace the power supply electrolytics on my Rogers Cadet 3 (integrated version). I have attached the schematics for both the control circuit and power amp below.

The caps I am looking to change here are the following:
Amplifier: C8, C9, C10, C11
Pre-amp: C12, C13

The power amp C8-C9 pair and pre C12-C13 pair are actually dual 24uF+24uF capacitors. Interestingly, the parts list for the rogers suggests 16uF instead of 24.

The power amp C10 and C11 are standard single cans.

So, onto the questions:

1. Can you please advise me on what I should be looking for when choosing a replacement for all the above? As the rogers is a low cost amp, I would ideally want to spending no more than a few pounds/dollars on each of them. At the same time I would I will get something inappropriate for audio, particularly as Rogers amps tend to have a bit of a hum at their best.
2. Finding 24uF+24uF is proving rather challenging. Does anyone have a source in the UK for these? Alternatively, can I replace with 15/16uF or 32/33uF and between the two options, which one is best and why?

Thanks a lot, take care,
Nikos

[SY]

C8 and C9 can be made larger without penalty (and perhaps with some benefit); 50-200uF is not unreasonable. C10 and 11 could be slightly larger (better regulation), but this increases the strain on the rectifiers and transformer because of higher ripple current, so don't go crazy there. I'd stick to the original values, if possible and not sweat going as much as 50% higher- after all, the original caps probably had a 40% upper tolerance.

Likewise, C12 and C13 can safely and profitably be made bigger- the resistors limit the ripple current.

Use caps rated at 105 degrees for reliability.

[cr0wl3y]

Thanks SY!