FSFR2100 SMPS Repair

[dundee]

Hi Guys!

Im trying to repair a SMPS based on a FSFR2100.
Datasheet: http://www.promelec.ru/pdf/FSFR2100.pdf
It is part of my Audio-System (no schematics available).

Actual Situation:
-Standby Voltages OK

I get 25V at the output without load. It should be 32V. If i connect a load the voltage goes down to 20V (if i draw 700mA).

Any ideas, what could be the problem?

Pictures Tomorrow...

[tautech]

How are you measuring voltages, a DMM I'd guess but have you checked for excessive ripple, the frequency of which may exceed the capabilities of your DMM.
So blindly going forward, check secondary side caps, diodes and possibly the feedback opto.

[wraper]

IMO either electrolytic capacitors on the secondary side are dead or something wrong in the feedback loop.

[dundee]

I changed all primary and secondary electrolytic caps.

I measured 1Vpp Ripple at the 320V behind the rectifier.

I'm wondering about that. I changed the two 330uf/200V caps against new ones.
Could they be the problem?


Here can see the supply in original condition: