Just the thermal LED shows , also with all 5 amp modules unplugged from the rack. Nothing looks bad , driver transistors and rectifiers, large Rs and caps sloppy-test cold ok , fuses ok , etc. Looks like the ST VIPer 12A , SMPS driver IC, data out there, powers a donkey engine SMPS then the main when the cold side control logic says ok to do so. I assume a schematic is not out there anywhere
traces and ribbons from PTC thermistor on the main SMPS Tx are ok to the control logic. I don't evenknow whether the ps will run with no working PAs plugged into the power bus. Next thing to trace , before probing out reduced-hot
All the chippery, I've found datasheets for, so maybe resolvable without schematic. What I thought was a uC (with buried FW of course) is a crystal controlled second SMPS controller for the main ps, and control logic is hardwired as CMOS 4000 and opamps
First small SMPS is in burst mode, presumably thermal shutdown (falsely or validly not determined yet), and cycling to restart every 30mS, so reduced supply voltage with nasty sawtooth superimposed. At least Viper
12A are easily available, hoping not due to shorted turns on the small inverter TxReplaced the primary SMPS IC and same poor DC supply . Determined it was not due to excessive load, shorted turns in the inverter Tx unlikely. Tried the secondary SMPS powered from bench ps and that brought up the internal Vref , requiring a supply of 10V , not 8.6V which is just below the undervoltage lock out. The Vref supplies the "thermal" LED opamps etc. Went back to the first SMPS and placed 4.7uF across the little 2.2uF SMD aluminium electrolytic that smoothed the sense voltage and the DC supply came up to 13.2V. So bad ESR cap again it looks like, falsely telling the IC that the Tx was overloading, rectified sense voltage was too high. The opto coupler was not for the primary SMPS, coupling is the other way round, probably to pass mains AC-ON confirmation, to lock out the 24V DC option, not used , as only mains use . Will tidy up cut traces and should hopefully be back into operation. About 2,500 GBP amp and as a not current model and long wire HV ducted cabling and transformered speakers etc, perhaps that again if a replacement 5 ch distribution amplifier was not compatible and all the other kit had to be replaced also
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