SMPS over voltage?

[tronick]

Hello! I am repairing two 120VAC in, 24VDC @25A out power supplies with matching failures. The fans stopped running and a long slow over heat occurred until a capacitor failed in both. I replaced the bad capacitors and checked everything else within reach and they power up OK. They are producing smooth 24VDC. However, once a load is applied drawing any more than about 2.5A, an OVP or over voltage error occurs causing it to shut down and illuminate the OVP led. The output does creep up to around 26 VDC before shutdown. Incidentally, there is an audible hi-freq 'squeal' heard from the unit once a load is applied that continues after load is removed, before tripping the OVP. I have tested everything for obvious failures with a DVM and all other components seem 'OK' so far. I have also replaced the opto-coupler and 15V regulator, no change. What would cause the supply to be unable to be unstable under a load? Thanks for any help! Will try to post a schematic as well.

[m k]

So feedback is leaving behind.

Internal 15V must be enough and remain like that.
U102A pin 3 is feedback voltage.
U101 pin 7 is feedback current.