Common issue of "only powers up when tape deck running"

[m40dotcom]

Wanted to make separate thread for this common issue as it seems like there should be a common fix.

(Playing off JVC Floyd's 838 post here... https://boomboxery.com/forum/index.php/topic/19630-jvc-rc-838-switch-problems/?hl=%2Bpower+%2Bnot+%2Bworking )

I have the same 'only powers up and works when deck is running' issue on an 838 and now a Sharp GF575 I'm working on. So it seems like it's a common issue across brands and models, etc. I'm hoping that as a collective group we might have figured out the fix for it, or at least the most common solution.

devol-toni and others had posted in that other thread but not sure if we had a good fix for this power related issue vs the left/right ch issue on the 838

Anyone have possible solutions for this common issue? Or even specific to the 838 or Sharp GF575 (which seems like same power switch style as 777)

Thanks!

 

[Beosystem10]

I suspect that it's the same switch as the GF-555 also. Mine stopped working unless one or the other of the motors was active and the reason isn't just the switch itself which is a generic part that was under €3 from Maplin. When a tape is played, the switch doesn't need to be in the on position so there's a supply rail that bypasses the switch to the rest of the chassis, the tuner being selected or isolated by the function switch rather than the I/O switch. This means that, when the switch fails the contacts in the on position, to get the power to the amp, tuner or lights, the motors will supply these circuits without that supply going through the switch.
I just tried my 555 the now and found that, by putting a tape in either deck and pressing play to keep that supply going, then the radio, line inputs and phono inputs could all be selected even though the (fully working as it should) I/O switch was in its off position - in other words as you'd expect it to do if you wanted to use a tape as an off timer for another function.

My solution was to take the old switch into the nearest Maplin and ask if they had something to match, buying it then fitting it. Job done and the facility to activate the other functions is intact as that uses the tape transport controls to supply independently of that switch.

I don't have any of these other boxes in front of me right now as 1) I only own one from the list and only have my 555 away from the house with me and 2) I'm on supply all week so won't be home to check, but I suspect that this fault could affect any box with a sleep timer that uses its cassette deck(s) to shut the whole machine down after the time it takes a tape to run through.

 

[m40dotcom]

Oh, so the issue was in the switch itself, and after swapping the switch it was back to working fine without having to use the tape functions? I was about to try and tear my switch apart but it didn't look like it would be fun/easy without having to do some solder work I believe.

Thanks for the reply. Figured someone had to figure it out.

 

[Beosystem10]

You're welcome. There's no reason not to take apart a switch and attempt a repair, my main reason for replacing rather than fixing is time and my chronic lack of it thanks to a hectic schedule.
By pulling an existing switch apart and attempting a fix that stands a very good chance of being successful in the hands of someone with a delicate touch, there's absolutely nothing to lose when that switch could, ultimately, be replaced. Nothing apart from a couple of hours (at most) out of leisure time for someone with the luxury of time to spare.
In the case of the GF-555, the switch toggle is part of the same moulding that activates the contacts, no external cover on there, so I did in fact end up taking an hour to cut the toggle off the set's original switch and attach it by fitting a steel pin along with a patch of suitable solvent cement, to the replacement switch so either way, I was destined to use up pretty much the same amount of that rare leisure time.