Technics SA-DV290 Repair

Symptom: Technics SA-DV290 "dead". Initially the standby light still glowed but then it, too, died.

Traced fault to Q726 (2SC3940AQ transistor) which is used as a 6v regulator.

Collector = 11.7v (slightly high) should be 10.7v
Base = 5v (wrong) should be 6v8v
Emitter = 5v (wrong) should be 6v

The transistor is difficult to reach without complete dismantling so I simply desoldered it and fitted a replacement to the rear of the PCB. I used a ZTX653 (1 Amp, 1 Watt).

Note: to test the unit it is necessary to connect a 47k resistor between the -ve of C740 and pin 3 of connector W902A. This will allow the unit to come ON when you press the Standby button. Then it will write H E L L O on the display.

47k resistor connected between -ve lead of C740 and a pin stuck into lead 3 of the ribbon cable WR902A.

With this connected, pressing the Standby button should turn the unit ON.

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