Revox A77 Channel 1 problem

[reely]

I just got an A77 up and running. I'm able to monitor both channels but when I switch the input to NAB there is a hiss and hum in channel 1. It makes no difference if the tape is playing or not. I've given the heads a good clean, tried cleaning the selector switch and played different tapes. None of this has affected channel 1 (though channel 2 sounds great) so I'm assuming it's not a record/playback issue. Hoping someone can help me.

Best,

David - Just a Revox A77, for now.

[ironbut]

Hey David,

Welcome to the forum.
Just so we get all the details straight,..

Does it also happen when you switch to IEC?
Have you tried switching the output cables left to right and does it happen when you monitor with the headphone out?

One thing you could try is cleaning all the multipin connectors inside of the machine. You do need to be extra careful with these machines when you pull those connectors though. The circuit boards in old A77's can get pretty brittle so you need to be very gentle. If you crack a board the machine is toast!

[reely]

Thanks, Steve. Yes, same problem with IEC, switched outputs and headphones. Are the multipins located at the bottom part of the machine (if it's standing upright)?

David - Just a Revox A77, for now.

[ironbut]

David,

IIRC, the circuit boards are mounted to the faceplate and bottom inside of the machine.
You should probably have the schematics handy.
You can download them from HiFi Engine

http://www.hifiengine.com/library.shtml

You could be better off just taking the machine to a repair guy since checking the internal connections is just a first try for folks who have some experience fixing gear. Come to think about it, many of the connections are edge pins on the boards themselves and like I said, they can be easily cracked.

[reely]

OK, I'd rather not do more damage. Thanks!

David - Just an A77, for now.