-- the RED SOCKET HELL --
I've also run into lots of machines with intermittant problems - everything from audio cutting in and out, to tape transorts not working correctly. Sometimes you can jiggle a few ICs and get the transport back working, othertimes nothing will work. then bang! the next time you turn it on everything works again. In emergency fixes I just have enough time to replace the worst of the bad sockets, and tell the client that he's got to have them ALL done ASAP - and of course he won't have it done... and I have to come back in a few months to do a quick fix once more.
So in the long run, you'll save both money and your hair by either hiring a good soldering person or doing it yourself - to replace all the Red Sockets. Just trust me on this one folks... go do it right now!
So you can pause a moment and think what this would do to the audio passing through a bad socket - it's got corrosion (which leads to intermittant contacts), and the connects might be good one second and not even there the next. The corrosion can act as a capacitor one second, turning a straight forward circuit into a wierd EQ, or instantiously changing the impedance of a circuit, and doing all sorts of other nasty stuff to your good clean sound.
So, in order to make your own MCI machine - tape recorder or console - work in a reliable way, you've just GOT to bite the bullet and remove all the red sockets - and I mean all of them - then install new high-quality "dual wipe" sockets.
Someone once emailed me asking what the 'red sockets' looked like..... well they are RED to begin with.... here's a picture:
They're everywhere... in the bias card, in the record/sync card, in the repro card, in the audio control card, in the VU meter buffer amps, in the Capstan servo card, in the lamp driver card, in the transport tension control card, and finally - and worst of all - they are also in the damn MOTHER BOARD for the transport!. Yep, that means removing the Mother Board.
It's hours and hours of dull boring work, but it's gotta be done.
Note that in a good socket, the grip between the wiper-arm makes an air-tight connection.... thus in a good socket there should NEVER be any corrosion in the area where the socket wiper meets the IC legs...