122mkIII - capstan takes off at hyper speed after recap


Jun 29, 2014
This is the 2nd time I've recapped a mkIII machine. The first time, no problems. This time overhauling was business as usual, then I put in a tape. It sounded fine, so I let the tape keep playing. About 20 minutes later I walk out of the room and hear a weird noise, then realized the speed of the tape had taken off to hyper speed. I rushed back in and turned it off.

I played the tape again, listening, and about 15 minutes later the machine sped up way high, then came back down, a couple times. After wigging out for about 15 seconds it went back to normal. I wonder if this has something to do with the Pitch Control... This is actually a NoS machine and this is the first time it's been used. Not sure that info helps any.
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Update: after a few minutes the capstan stops and I get the tape-stop effect as mentioned above. This time I let it sit for a few minutes afterward. I began hearing a weird sound like the little needle thing that moves across a hard drive platter. And the sound isn't the capstan either. That stops spinning at that point:

I started carefully feeling around and noticed that the BA6411B IC was getting VERY hot to the touch. This explains why it works for a few, shuts off, then I have to leave it off for a bit to get it to come back to normal. I think that might be what the source of the sound is. I'm unsure if replacing the IC is what I need to do, or if something else is causing it to get hot that should be fixed.

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