I bought an old Blaupunkt Bremen cassette player off ebay as I thought it would be in keeping with the original look (Square dash 944)
The only problem is the stereo I bought had not been powered up for years so the caps inside were drained and pretty useless so the thing didn't work until I managed to get some charge in the caps.
I'm no electrical expert but this is what I did to get it working and it maybe usefull to someone who has bought an old stereo or is considering buying one.
I found that if I connect the stereo to a 12v dc power supply I just get a light on behind the on/off switch but if I leave it connected for around thirty mins and then touch the blue antenna wire to the positive wire the unit works after 5 seconds.
As long as I keep the radio connected to a permenant supply the stereo will work again when I turn it on but if I disconnect the power I have to touch the blue antenna power wire to the supply again for it to work.
And if I leave it disconnected for an amount of time I have to wait 30 mins for it to work again using the antenna wire.
It took me and a mate a lot of messing around to find this out but my stereo now works.
I've wired it permenantly on so I have to switch it off even when the ignition is off and I've put a switch on the antenna wire for when I have disconnected the battery.
Hope this is of use to someone and I'm sure an electronics expert can explain the hows and why.
Lee