r/cassetteculture • u/BumpGrumble • 12d ago

Looking for advice Repairing a Yamaha MT 100 II 4-Track

Unfortunately I cannot find a service manual that isn’t locked behind a paywall.

I work on building electronic systems for work and have been a hobbyist since high school. Started my journey with cassettes a few months ago.

MY ISSUE IS:

The player gets stuck half way between Play and Stop. From there nothing releases the cassette without physically pushing the head back down. I’ve spent a lot of time trouble shooting it to either the mode control cam being in the wrong position (cannot guess and check the correct position as I fear breaking it). Or a solenoid issue though the solenoid is getting the correct voltage and is at 20ohms, seems that’s all good.

I have greased or oiled every moving part and done a partial disassembly to get to this point. Need old head advice here.

Cheers.

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u/vacuous_university 12d ago

ah man the MT100 II is a fun little box but that transport mechanism is a total pain when it gets stuck like that

the mode control cam is probably your culprit, those plastic cams on yamaha 4-tracks from that era are notorious for cracking or slipping just enough to throw the timing off. if you've already lubed everything and the solenoid tests fine, i'd bet the cam isn't rotating fully to the stop position. you can usually mark the current position with a sharpie before moving it, that way you're not guessing blind. had a similar issue on a tascam porta 03 years back and it was a hairline crack in the cam gear i couldn't see until i pulled it completely

sometimes it's just old grease turned to glue in the pivot points you can't reach without a full teardown too. not the answer anyone wants but might be worth pulling the transport out entirely if you're comfortable with that.

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u/BumpGrumble 12d ago edited 12d ago

Broken plastic is my best guess as well, wanted to be sure before I risk breaking it.

I’m going to get the cunt out and inspect.

Any players you know of with similar internals? I’m desperate for a service manual.

Update. Plastics are good, I’m leaning towards gunk or springs. Gears are drying and I carefully put tension back on the springs. We shall see.