Strange power problem with Sharp Mid-Drive VCR VC-H86

[[email protected]]

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.

 

[[email protected]]

In the power supply is a 47uF 16 Volt electrolytic.
Probably C902.
Replace the S.O.B.

 

[[email protected]]

In the power supply is a 47uF 16 Volt electrolytic.
Probably C902.
Replace the S.O.B.

 

[Skype_man]

Do as moeee posted, & check all the electrolytic capacitors
in the power supply, as well as diodes, etc. Sky.

 

[[email protected]]

Hi and thanks for the help. What I ended up doing was advertising it on
our local version of eBay for a dollar and, when it didn't sell, I
reckoned that was a karmic sign, so I used a bit of reverse psychology
on it. On the basis that it had stopped working after power was removed
for three weeks, I disassembled and reassembled it so that it would
power up (as described in my original post) and then just left it
connected in a powered-up state overnight (displaying the "Sharp"
logo), before trying to operate it or press any buttons.

In the morning it was working perfectly, and still is a week later.
Strange.

If it fails again I will certainly try replacing the capacitor. In the
meantime, this baby's never going to have power disconnected again!

Thanks again to you both for your help.