UNI-T UTP3305 power supply repair

   Unfortunately my workbench power supply stoped working properly. It is UNI-T UTP3305 model. The problem is described by another guy here https://www.youtube.com/watch?v=Qb57Hz752HI

 Thanks to him i could locate problem a lot faster. He suggested to look at supply filtering caps(they can be shorted). In my case C25, C7.  But when i was looking for the problem power supply died completely. And it was faulty flip flop IC with designator U10 (bottom left). I suspect U10 was not working properly before he died completely(because sometimes supply worked sometimes not). I think when the relay switches or current limiting occurs there are nasty voltage spikes. And U10 has long supply tracks without any local decoupling cap. I am not sure, but that could be the reason for failing. I have added additional local decoupling and hope it will work forever :). So far so good....

UNI-T UTP3305 problem repair

Pic.1 UNI-T UTP3305 control board