exxos's Atari, Amiga & retro forum

Hi,

I ordered your cap upgrade kit and I'm in the middle of installing the new caps when I noticed they are not the correct volts:

I have the Atari STFM ASP32 Kit which on your webpage states:

Capacitors are
250V 33/47uF x 2 - Replaced 250V 47/68uF
35V 330uF x 3 - Replaced 470/820uF 35V
16V 4700 x 1 - Replaced 4700uF 16V
16V 2200 x 1 - Replaced 4700uF 16V

But the caps I have received are of a lower voltage than the ones I'm removing which I am concerned about :
350V 33/47uF x 2 - Replaced 250V 47/68uF <-- Originally 350v
35V 330uF x 3 - Replaced 470/820uF 35V <-- 680uF 25v is what I have been sent
16V 4700 x 1 - Replaced 4700uF 16V <-- This is OK
16V 2200 x 1 - Replaced 4700uF 16V <-- This is OK

Please advise, thanks.

Its correct. 16V is good for 5V and 25V is perfectly good for 12V. Even some of the original power supplies don't all use the same voltages either.

exxos wrote: 08 May 2026 20:25 Its correct. 16V is good for 5V and 25V is perfectly good for 12V. Even some of the original power supplies don't all use the same voltages either.

OK, great, Thanks for clearing that up.

BTW, probably to late to note which way you took the old caps out, but don't depend on the silk screen being correct.. I can't remember which PSU's but some have the silk screen BACKWARDS ! So always check the NEGATIVE side of the main caps is actually going to 0 V !

Thanks for the tip, I took photos before I swapped out the caps to make sure I didn't mess it up. Although once removed I could see they'd applied the right silk screen showing the cap orientation correctly. Now my ST works again - Hooorrraaaayyyy!!!

Thanks for all your help and tips.

ChrisA wrote: 08 May 2026 18:34 350V 33/47uF x 2 - Replaced 250V 47/68uF <-- Originally 350v

You have replaced a 350v cap by a 250v one? Is this on a PSU to be run in 110v land or with 230v supply?

MasterOfGizmo wrote: 09 May 2026 11:50

ChrisA wrote: 08 May 2026 18:34 350V 33/47uF x 2 - Replaced 250V 47/68uF <-- Originally 350v

You have replaced a 350v cap by a 250v one? Is this on a PSU to be run in 110v land or with 230v supply?

Yes, the 250v one replaced the 350v one to be run on a 230v supply.

ChrisA wrote: 09 May 2026 12:39 Yes, the 250v one replaced the 350v one to be run on a 230v supply.

230 V AC will have peak voltages of 325 V and you usually apply some derating on top of that. So make sure your caps are rated for 250 V AC in that case and not 250 V DC.

redpixel wrote: 09 May 2026 14:54

ChrisA wrote: 09 May 2026 12:39 Yes, the 250v one replaced the 350v one to be run on a 230v supply.

230 V AC will have peak voltages of 325 V and you usually apply some derating on top of that. So make sure your caps are rated for 250 V AC in that case and not 250 V DC.

I got the caps from the upgrade page on this site so assume they are 250V AC but looking at them it doesn't say AC anywhere.

I got kit number 0028.
https://www.exxosforum.co.uk/atari/store2/

@ChrisA don't worry, @exxos will. Have selected correct caps for his replacement kits.