Entropia: Your gallery hosting software looks great! Is it open source, by chance?
Nope, it's a bought service, the software is prorietary to the gallery service provider.
Anyway, some progress, I guess. Cleaned all the boards "enough" and tried plugging in the power. It draws a constant 150 mA with only the battery+ terminal switched. If I connect the ignition-pin to 12V the current draw doesn't change. 150mA is way too much for "sleep" current anyway. I've been searching for a service manual / schematic like mad but there just doesn't seem to be one on the internet. I even asked the Finnish authorized Blaupunkt service but they said they don't ever get the OEM stuff manuals. Dead end. I could ask Blaupunkt at Germany directly but frankly I don't expect any miracles...
Someone suggested desoldering all the parts but that's just out of the question. I tried to solder a few testpoint wires to various power supply components but frankly, it's impossible. The corroded solder will not melt. I even blasted the solder at 450C for as long as I dared but nothing. I fear the PCB tracks will lift off before the solder melts. I tried applying shitloads of flux and using good quality solder but in vain.
Tracing out the circuits is also impossible. The main PCB seems to be 4 or 6 layers. This is turning out to be a harder than I thought!