Strange one, this, and I'm hoping someone here can give me some clues.
My Sharp mid-drive VCR model VC-H86 was working perfectly up until I went away on holiday. Before I went, I turned it off at the mains. When I returned 3 weeks later and switched it back on again, it powered up fine. But after a few minutes if you press the "Operate" (soft-power) or any other buttons, the display goes blank and the power supply emits a faint high-pitched whine, and that's all it does. Unplugging it and plugging it back in does nothing - it's still "dead".
If you don't touch any buttons, it'll stay powered up for as long as I've left it (well over an hour). But then touch any button (on the unit or the remote) and it goes dead.
If I unplug the internal power supply multi-connector (so the power supply is isolated from all other circuitry), it seems to be providing power OK from some of the pins on the multi-connector, but is still making the same faint whine. Plugging int he multiconnector again, it's still "dead".
Even if I unplug it and leave it for a week, it still won't do anything when I plug it back in. Still seems completely dead. But....
If I unplug all the internal ribbon connectors and physically remove the power supply, and then replace it (this is a simple operation by the way, takes about 5 minutes if that), it will power up again and remain powered up until I press the "Operate" (or other) button then its the same story all over again. When it's powered up, the supply doesn't whine.
Why would it fail after 3 weeks without power, when it was working perfectly before? Why won't it power up no matter how long I leave it, but will power up if I dismantle it and reassemble it?
My first thought was "dried up electrolytics" - do they just dry up when not in use? Anyway, I've checked the ones on the power supply board and they seem fine, and as I say, the supply does appear to be delivering power. Can anyone give me any other ideas on where to start, other than a new power supply, and I'm not even sure it's the supply that's faulty.
Thanks.