Teac A R650MK2 Amplifier Repair (With Audio Tutorial)

Fault 1
Amplifier in protection mode, Power LED flashing red.
Failure of the left channel.
Following components replaced.
Sanken Output Transistors
Q518 - 2SC3519A & Q520 - 2SA1386A
Resistors
R535 680 Ohm 1 W
R536 470 Ohm 1 W
R532 / R533 100 Ohm ¼ W
R533 / R538 Ohm ¼ W
Bias for each channel set to 5 millivolts.
Fault 2
Power switch sticking.
Metal mounting plate removed and re-aligned.
Fault 3
Intermittent loss of sound left channel.
Volume control / pre-amplifier board connecting pins cleaned with a fibre glass pencil.
Socket on the Tone Board cleaned with De-Oxit.
Amplifier fully tested working correctly.
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[@chrissmith7069]

Excellent Gary.. Thank-you 🎉

[@AudioAmplifierServicing]

Chris thank you

[@reamer82]

Great watch . Ben

[@AudioAmplifierServicing]

Ben thank you

[@cuttysark7034]

Did I understant you that you have to remove the resistors to check them? Can't you just check it in situ with a multimeter?

[@AudioAmplifierServicing]

Hi It is possible to measure resistors in circuit, but it may not be possible to obtain an accurate reading.It depends where in the circuit the resistor is located.
It may be in parallel with other components resulting in a reading that may be misleading when fault finding.
It is better to lift one end of the resistor or remove it.
Also ensure your finger tips are not making contact with the multimeter probes tips otherwise your measurement will again be inaccurate as the meter will measure the resistance of your body as well as the resistor.

[@cuttysark7034]

@@AudioAmplifierServicing cheers