Blaupunkt radio ceased working

[lagonda 41]

When squatters stole my CTi it drove the only benefit of it driving so badly is that they dumped it back in my driveway. They did take the radio, which I replaced with a Blaupunkt London MR21 radio cassette player. This has worked fine since 2005, but in recent years, switching it on became more and more variable. Usually it would come to life immediately, but sometimes you would have to wait, and it would suddenly light up and play. Once on it would stay on. Those non-working occasiuons became more frequent, and now, nothing happens at all. No lights, nothing.

 

I suspect the on-off switch part of the potentiometer volume control, but having taken the covers off the set, that component is pretty inaccessible. This fault also occurred many years ago with another radio in my then car, a Lancia Y10, so perhaps it's endemic to car radios! Wondering if anyone else has encountered similar and has discovered a straightforward fix? I'd be happy to bypass the on-off switch and use an external switch, but how to connect?