[Lidingo]

I have an old Sansui AU-999 that I think need new capacitors in the power supply (the two big ones at least).
Could I swap the originals for capacitors with greater value and is there a limit when the values get to high?
Could I put a pair of RIFA 10 000uF 63V in there instead of the originals?
I've seen that others put a smaller capacitor along the big one as well. Whats the benefit of that compared to choosing a bigger one to start with that has the same value as the big and small capacitor?

[paul79]

You can up the values of these, sure. I assume you are doing this because modern replacements run much smaller than the originals, correct? And you want a factory look using the same clamps?

If I remember correctly, this amp uses 6800uf filter caps? I see no problem using 10,000uf for these. The only thing you really need to worry about is the power switch taking a bigger inrush hit, as the transformer and the bridge rectifier are more than beefy enough to handle it.

This amp is over 40 years old, and it very likely needs more caps replaced than just the power supply caps.

[Lidingo]

Thank you for the confirmation. The originals are 4700uf and 50V and I can not find new caps with that value.
The smaller caps are more easy to find with the exact same value.
I will change these also at the same time as suggested.

Wanted to know if I could exceed the 50V with the 63V caps, my understanding is that the caps degrade quite fast if to high V cap is put in since they don't ever nearly totally unload. I could be (probably is) wrong regarding that but I remember hearing it a while back that they degrade faster if to high V is put in there. How high Volt value is to big then?

[paul79]

Using a higher voltage cap does not hurt anything with regards to reliability. Opposite, in fact.

In this application, the lower ESR of the higher capacitance capacitor will far outweigh the benefits of getting the voltage rating close to the actual voltage present. Put the 10,000uf caps in at whatever voltage you have to in order to get the right diameter to fit. You can use higher voltage rating, never less.

[Lidingo]

ok, thanks.
I e-mailed the seller on this site:
http://www.audio-high-store.com/product/sansui-au-999-upgrade-kit-audio-capacitors/
they sell replacement cap kits for au-999. I asked about what values they supply in the kit, hope they answer.
Seems like they supply quality caps of known brand of caps, but hopefully I get an answer soon and can compare their values with the original.