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Revox B710 MKII Counter and sensor repair (Repairs play, ffwd, rew)

Ryan Hall

New Member
HI all, been working on this deck for three months, and finally have it working. Sharing my repair process.

Warning, short circuit will ruin your sensors

First, whenever you are working on this deck, unplug it! The sensors have exposed circuits, and if they touch the chassis while it is plugged in, it will short and burn out the led sensors. In my case the counter stopped working, and therefor ffd, rew, and play no longer worked, because the processor wasn't receiving signal from the sensors.

Repair parts ordered:

Ebay
Replacement reel sensors
Replacement end of tape sensor

After replacing these parts, the counter began working again, and the end of tape sensor would wind the tape correctly. However on playback, it stopped after two seconds. After hours of troubleshooting, it turned out the issue was with resistor R81. This is a variable resisitor, which ajdjusts the strength of the signal coming from the ir leds to the microprocessor. The signal was too low, and wasn't reaching the processor, making the deck stop because it thought the tape was over. After increasing the level on R81 (it has a white dial on it), it started playing back perfectly. However, the rewind stop functioning. This was due to some cold solder joints on R81 and the surrounding area. Once I reflowed all the solder joints, everything started working again with no issues.

Hope this helps someone out there.
 
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