Video length is great.

Outstanding! Like a surgeon, always a pleasure to watch a craftsman. Bravo. Thank you sir.

Another great video, thank you! Appreciate the effort and patience you always apply, there are very few great audio repair videos on youtube. Yours certainly one of the best!

Congrats on 10k subscribers Trevor.

Some of the plastics from the '70 shrink, and when they are cast around steal or iron it cracks because the metal won't budge. About the head setting, most cassette decks have only one screw for the azimuth, tape decks can have more. I would not compare different frequencies for a phase shift, but only 10kHz for maximum output. And when you have do it by ear, listen to the signal in mono (e.g. short L+R on the headphone), it is then easier to spot.

A shame no one ever made belts that last. Amazing engineering in cassette decks all dependent on a piece that turns to mush.

The playback keys would all come up very nicely using the Retrobrite rejuvenation process (hydrogen peroxide and UV light or sunlight).

Nice job and congrats on 10k subs! You might pop the back of the motor off as it probably contains 1 or 2 electrolytic caps in the driver circuit.

Some people think that plastic "shrinks". I never saw that happen with my eyes but who knows why some plastic shrinks and the other ones not, why only one buttons shrinks? Makes no sense to me. E.g. I never saw a computer case or keyboard shrinking but gears do shrink? Not sure about that theory, to me plastic is a solid material. Metal also expands when heated up, so what shrinks and what expands? I guess those push down levers are just a bad design, I had an old Philips and they also were very thin push-down buttons and most were broken off from use or handeling the device. That one key breaks in different spots is kinda unusual because why should the stress be on 3 points and not be released on the first crack? Probably a mix of pressure and bad material. Maybe those were exchanged, bur the plastic did not yellow, I think yellowed plastic is weaker and gets more brittle, I had computer cases that just shatter to pieces, but then you take the same model and that is still fine, so the most important is the plastic material. If it is bad, it is bad. E.g. one gear in Macintosh floppies goes yellow and fails, while the other ones are fine. Some gears do not shrink and crack, but other ones do. I guess it is more a quality issue of the plastic, and the implemented safety features (some say the fire retardend chemical stuff makes it yellow). I see some keyboards have only a few keys yellowed - same sun and environment, same manufacturer, same date, same plastic, same color - but different results in the long run. Some keyboards will NEVER yellow, always the same type is white as new, and other types always yellow, or partly yellow. No one really can explain it, but to me, yellowed plastic is broken, it just lost its properties and will fail or crack. My theory is if it would be true that the plastic shrinks, what would happen if you heat the metal pin to melt the plastic to the new size, but not sure if that would impact the performance if you overdo it. But in theory the plastic should kinda get the shape of the metal and thus should not crack - but with sich various results and materials and thing no one could be sure what is best to do. As I said, mostly it is always the same part that fails, and that has more to do with the manufacturing and not the fact that it is metal on plastic, as many many many gears are still fine, even in the same assembly with the same conditions and same properties over the same time.

Hate to nitpick, you checked azimuth, but did you check tape speed? I understand it must not have sounded too far off.

My 1st cassette was a bottom end JVC, lasted couple of years before mechanical activators broke 1 by 1. I remember those days late 1970's record album onto cassette for the "high bias" because commercial recorded cassettes lacked clarity and in late 70's if you listed to an 8 Track, you were an idiot. That is wild how you can rotate the transformer. Interesting trick with dental floss where a Zip Tie would probable be too big, when the timer breaks on my Kenwood 9000G breaks, like that UV Dryer. Country, he is pretty popular here in the States, all though I hate country music.

VIDEOIS TO LONG

i have not seen such an old device on my bench. Good job!