Here's my old post of mine from S2G. It has been updated with additional info and pics. 
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When Freddie came up to visit, my GF-9494X tape deck decided to die. We were both jinxed that day so I really couldn't beat his ass for it.
There was a dreadful motorboat hum and squeal. I rarely played cassettes with it, so didn't know the problem existed until Freddie "discovered" it. It wasn't a problem when I first got the GF-9494.
On the advice of Vladi, I got liquored up and went to town spraying contact cleaner everywhere inside the box.
Unfortunately, it didn't work - the cleaner that is. I then tried the old "play/record switch" trick and must have worked that for about 15 or 20 minutes. Eventually the hum was completely gone!! 
But, the bad news was, the capstan tire had turned to goo somewhere along the way also. So, I had to open it up and get in there. After a bunch of screws, a green wire, and at least one connector, the tape deck mechanism was free and then the real fun began.
Sure enough, the capstan tire was goo.
I still had some silicon tubing left from my last capstan tire repair and cut off a little piece (the original capstan tire is on the right).
While I was in there I sprayed a double shot of cleaner into the record switch underneath the cassette mechanism. The next thing I had to do was clean the black-goo-from-hell off another rubber tire and the play wheel. GooGone and about 9 double-ended Q-tips later, the wheel is finally clean and I was able to clean up the old rubber tire a bit also.
Testing revealed everything was okay so I put everything back together and popped in a reel tape of mine just to make sure I didn't forget to hook something back up. Booyahh! I'm back in business!!
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When Freddie came up to visit, my GF-9494X tape deck decided to die. We were both jinxed that day so I really couldn't beat his ass for it.
There was a dreadful motorboat hum and squeal. I rarely played cassettes with it, so didn't know the problem existed until Freddie "discovered" it. It wasn't a problem when I first got the GF-9494.On the advice of Vladi, I got liquored up and went to town spraying contact cleaner everywhere inside the box.
Unfortunately, it didn't work - the cleaner that is. I then tried the old "play/record switch" trick and must have worked that for about 15 or 20 minutes. Eventually the hum was completely gone!! But, the bad news was, the capstan tire had turned to goo somewhere along the way also. So, I had to open it up and get in there. After a bunch of screws, a green wire, and at least one connector, the tape deck mechanism was free and then the real fun began.
Sure enough, the capstan tire was goo.
I still had some silicon tubing left from my last capstan tire repair and cut off a little piece (the original capstan tire is on the right).
While I was in there I sprayed a double shot of cleaner into the record switch underneath the cassette mechanism. The next thing I had to do was clean the black-goo-from-hell off another rubber tire and the play wheel. GooGone and about 9 double-ended Q-tips later, the wheel is finally clean and I was able to clean up the old rubber tire a bit also.
Testing revealed everything was okay so I put everything back together and popped in a reel tape of mine just to make sure I didn't forget to hook something back up. Booyahh! I'm back in business!!
what is the "old play/record switch trick" ? 
