Teac A R650 UR Amplifier Repair

Faults
Buzzing sound present on both channel with no inputs connected
Erratic input channel changing
Balance control temperamental causing loss of one or both channel
Speaker protection relays badly worn resulting in distorted Audio at low volume.
Volume control very noisy when rotated.

Occasionally Amplifiers arrive in the workshop with a bucket load of issues.
Many of the faults above only become apparent once one fault has been rectified and testing has been initiated.

The first issue was due to the pre-amp power supply electrolytic capacitors,
they are mounted close to the series regulator transistors hence had dried out due to heat.

C716, C717,C719, C718 100uF 50V replaced fixing the issue.

The erratic channel changing was due to the input selection encoder lubricating grease drying out causing intermittent operation.
Encoder removed from the tone board and cleaned with a fibre glass pencil and De-Oxit.

The volume control had to be removed and stripped down and cleaned again with De-Oxit to fix the noise issue when rotating.

Both Speaker protection relays replaced as shown in the video.

Finally the balance control Type 11 Dual B100K Centre dent D Shaft potentiometer has to be due to a cracked carbon track.

Bias for each channel checked no adjustment required.

Amplifier fully tested working correctly.