Kenwood KAC-6202 Shut Down Troubleshooting Tip

[kds9591]

Worked on this Kenwood Kac-6202 that had a shutdown problem. Amp shut down immediately and went into protect mode. Pin 3 on the TL494 chip was high @ 3.5 volts so I shorted that to ground to force the amp to turn on.

After the amp was powered up I adjusted the idle pots (VR3, VR4) to see if one or both was turned up too high and to see if one channel was not adjustable. The right channel was not adjustable so now I knew the problem was on the right channel. While comparing voltages from the known good left channel I noticed the voltage was wrong on the emitter of Q208. It measured about -5VDC volts, should be about -26.5VDC.

The transistor junctions checked out ok so I went to the solderside and followed where the emitter trace went to. The components on the solderside of the board do not have locations marked like the top-side components but I found a open trace coming from Q208 to a SMD transistor. The actual open or break in the trace was right off the pad of the SMD transistor. See photos, one is of the smd transistor and one is after a jumper was added to repair the open trace.

I hope this info helps someone repairing this amp with the same problem.