250 watt amp always blowing fuses after replacing transistors

[lilshawn]

Rowe 250 watt amp (common to 100 series CD units.) that would blow just one of the fuses on one of the driver boards once plugged in.

Traced to bad LM317 regulator on the Preamp board. depending on the mode of failure of the transistors a spike can feedback and blow one or both of the regulators on the preamp board to power it.

The fuses feed +40vDC and - 40vDC to the transistors to drive the speakers, but also feed back into the preamp.

powered up the amp with no preamp board replaced fuses, and verified proper voltages on the outputs to the preamp (+40vDC +/- 2 volts) on pin 1 and (-40vDC +/- 2 volts) on pin 2 of connector P1 of the driver boards.

replaced capacitors c99 c100 c101 for good measure and voltage regulator Q23. back up and running again 

[jdemarti]

Thanks for the tip, lilshawn. I'll have to keep this one in the ol' memory bank.