PC-8 tape controls

[Buck Rock]

So my Yamaha PC-8 is resting comfortably after its cross-country trip to me...but there seems to be a problem: it's the tape deck.
It's fast-forwarding and rewinding fine, but not playing. Every button I press, including forward and rewind the Dolby controls and even Eject, makes a weird 60 hz, "beam-me-up-Scotty" buzz that reminds me of a gone capacitor, or the sound you get turning on an old TV. It's a quick sound that fades up and down, and sometimes it even pans from one speaker to the other. Tape compartment looked a little dusty, and I did do some FaderLube on the sliders, but I don't think I can get to the buttons without cracking this guy open. And the buzz makes me think there's a more severe problem than just belts and cleaning can solve, like maybe a logic board problem. What do I really have here?

 

[floyd]

it could be the belts on the play motor are slipping or off all together and the whining sound is coming from the motor spinning all the time.I'm not sure if this has multiple motors or not like the pc55 does. But one motor runs fast forward and rewind and the other motor runs play.

 

[Buck Rock]

Definitely not a mechanical sound and not a whine. It's a low electrical buzz I only get when I press a button. Motor doesn't have to be running to get it. Barely lasts a second.

 

[Buck Rock]

Little further research...the "finger" sensors up at the top of the tape cavity are acting pretty sensitive and make the "tape type" lights flicker when I touch them. One in the group on the left is particularly finicky. There's a fine coat of dust inside that I can see as I move the tuner wheel, so maybe some of that dust has gotten in there deep enough to cause some interference with contacts. I may have to dive in for a thorough cleaning and see if that helps. The "zap" sounds on the transport and Dolby buttons did seem to change a little after some FaderLube but they're still there. Stay tuned for updates.

 

[Buck Rock]

Welp, I tried. Thing's SOLID inside. Lots of metal. Electronics are stacked in tiers and I could only get into the top tier so couldn't get behind the transport buttons down below. Settled for trying some more FaderLube in the sensors in the tape compartment. VU lights are no longer on when Tape is selected, but the zap sounds are still there and it still forwards and rewinds but doesn't play, so...I guess I made some progress? I JUST realized I forgot to get compressed air while I was at Walmart, so once I get that I'll dig in again. Advice still welcome.

 

[Buck Rock]

Squirted the compressed air everywhere I could get it into...still no joy. Although the whiny zap noises seem confined now to Foward and Rewind. Also noticed I can't seem to engage Record - button doesn't light up so apparently the signal's not getting through to the transport. Music search doesn't seem to work either. Head does reverse when the tape changes direction in FWD and REW so this is not a mechanical issue as much as an electronic one. Really trying for this dude because it's so rare but I'm starting to suspect the worst here in that I've got a gone logic board or capacitor, or possibly a busted sensor at the top of the tape well. I'm in uncharted territory here and judging from the number of responses, it looks like you are too. Please prove me wrong.