Goodmorning everyone,I have a SURT3000LXI ups where all the transistors and diodes of the heatsinks have been combined,the C720, the 2200Uf 450V of the positive branch, q728 and q729, vrified all the other diodes,resistors, ptc, mov and relays that all seem ok, the batteries are charged at 102V each block.I insert the batteries, start brain, fan runs, cold start ok, I give voltage,the relays move and the UPS charges the batteries, if I cut off the voltage or the batteries, the UPS works.There is a crackling sound in the c720 area which is usually normalI plug in a 100w load that turns on, but the load indicator and fan start athopping and the crackling becomes irregular. I remove the voltage the load remains on butthe fan and the load led indicator switch randomly even at full and idlecontinuously.By connecting putty with the serial, the PVREFP voltage changes randomly between 230 300V while PVREFN is stableabout 300V.Where can the problem be?Thanks in advance
