Got my $30 new-old stock Blaupunkt installed in the GTV6 finally and it works beautifully. Using in series with an old, spare 120w amp installed under the passenger seat with a low-level input for my iPhone, which is the primary source of audio in the car. Got a pair of pretty decent factory refurbished Kenwood 6.5" speakers for about 1/3 retail. Nice. Actually sounds really good, especially for such a patchwork job. The head unit is mostly for completeness, although I do enjoy the local Austin music station. I also have a box of 80s hair metal tapes that seem perfectly appropriate jams for the car.
So this was a brand new, sealed package Blaupunkt from the late 80s/early 90s, designed for the Merc E-class. Sometimes it'll play a tape, but most of the time it'll either warble for a second then spit it out, or proceed to munch the tape until I eject it.
Having trouble finding good diagnosis and solutions. I assume it could either be crustified lubricant jamming the takeup reel, or a dry-rotted belt slipping? The fact that it works perfectly sometimes makes me think it's not a terminal problem, or even something significant like a dead or dying motor.
Any old school car electronics buffs have any ideas? I'm going to have to pull it back out of the car anyway, to fabricate a better mounting bracket.