Tascam 122 Mk III capstan with dead spots


New Member
Apr 18, 2017
Gear owned
Lots of Tascam stuff!
Working on a Tascam 122 MkIII with a rather odd problem. I have searched and searched and only seen this mentioned in a place or two, and NEVER any honest solution.

My Problem: The capstan has a dead spot. Just one specific dead spot.

It is not the tape switch, nor is it the crap-caps or C2, or stuck gears or dried lube on skeleton switches or any of the usual culprits. I've fixed all that and more.

The machine mostly plays fine and will start and run just fine. But by pure happenstance, when the capstan happens to stop rotating at "POINT X" (which I have physically marked and verified) it will not run again.

I can physically move the capstan flywheel a mm in either direction and voila! Trigger the motor with the cassette insert switch it takes off and runs fine...until by happenstance it stops at POINT X again, which might be two or three or twenty or fifty times later. Same spot, totally random that it happens to land there.

Besides a capstan board recap, C2 replacement, full gear fix relube and cleanout of the brown glop, and the usual other stuff, along with a stereo-microscopic examination of the capstan board traces along with resolders of the Hall Effect sensor leads and some touch-up of suspect looking solder joints here and there, I haven't done anything else.

I was about to split the capstan board off the assembly and look at the hall sensors themselves a little more closely. But before I do that...

ANY suggestions are most welcome, and THANK YOU in advance for any ideas.

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