Sony TC-K620 (audio) cassette deck: (guide?) pin hum

[linus]

Spinning guide(?) pin humming / buzzing

Hi there, I apologize for the intrusion but I wonder if someone might be able to help me. Yesterday I bought a Sony TC-620 3 head cassette deck (ca 1990) from a local thrift Store.

It powered on fine at the store and all the functions appeared to work. When I got it home though and plugged it in and turned it on an audible humming/buzzing was apparent. The noise is present without a cassette in the deck or activating any of the deck's functions. It is also present regardless of whether it was connected to a receiver. It doesn't become louder or less loud while a tape is playing.

Upon further investigation I found that by opening the deck (as in ejecting the cassette tray) and pressing my finger against the spinning metal (guide?) pin (so that it slows to a halt) the noise nearly disappears. It appears then that the humming is somehow related to the operation of the pin.

I'm wondering if #1) anyone might know what could be causing the humming #2) if it will be require replacement of parts and which part(s) and #3) if part(s) would even be available. Otherwise, the deck appears to work well but the humming noise is a deal breaker for me (if it can't be fixed at a reasonable cost).

Thanks for any help you might be able to provide.

Best regards,

Linus

[linus]

To further investigate the source of the hum I removed the deck's top/sides cover (led in place by four retaining screws - two per side) and located the motor driving the "guide" pin (which as I would find out is called a capstan motor, and it is [in the words of the wise elders of Wikipedia] "used to move recording tape through the mechanism of a tape recorder." It is also used on this deck to power the opening and closing of the cassette tray.)

I inadvertently knocked the belt off the pulley driving the capstan and the noise was still present suggesting the possibility that the motor itself was the problem.

I googled the make and model number of the capstan motor (Panasonic MMI-6S2LK) and quickly found multiple forums discussing this motor and capstan motors more generally. Apparently these motors are all likely to fail over time and before they do they may become noisy.

I also learned that the MMI-6S2LK is now hard to find but that the apparently more avaialble Mabuchi EG-500AD-2B motor might also be used.

Cheers,

Linus