GF-9191 Bass / Treble Sliders Inoperative

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mcroce

Member (SA)
Hi, I recently bought a fairly good condition Sharp GF-9191H off of eBay.

So far, the only functional deficit that I can find is that the treble and bass sliders are completely inoperative - moving either or both of them produces absolutely no change in the sound.

I've got the unit completely disassembled right now for cleaning and I'm looking for recommended solutions on restoring function to the sliders.

I've ordered some DeOxit, and will use that, but because it's only these two sliders (the others work fine), and because it's a total failure (e.g. it's not intermittent or static-y) I suspect it's not just the contacts.
Does anyone have any recommendations, before I reassemble the unit?
 
MesaAZGuy

MesaAZGuy

Member (SA)
Check to make sure there aren't any cracks on the PC board. Check for bad solder connections. Aside from that, see if the DeOxit does any help when you get it.
 
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mcroce

Member (SA)
OK, I have the boombox reassembled. The bass and treble sliders still don't work; have cleaned them well with DeOxit. No visible cracks in the PCB. Any ideas on testing the potentiometers to see if it's their failure or a connection??

Thanks!
 
Superduper

Superduper

Moderator
Staff member
It is most likely the potentiometers. The failure is common. What happens is the brushes inside the control breaks off or gets loose and loses contact, or the pins that solder to the PCB have a break in the potentiometer resistor board. To test, you probably need to remove the Pot from the PCB to be sure although you can possibly try to test it in circuit but the readings could be all over the place due to potential parallel resistances and confuse you.
 
docs

docs

Member (SA)
If you google how to test a potentiometer and do a simple multimeter test, it will tell you if the actual tracks of the pot are good or not. Once you know the answer to this you can determine whether to open it up and fix what is likely to be brushes which have come unstuck from their mount.
if you get signs that the pot tracks are knackered by seeing readings which are waaaay off what the pots' value is, all is still not lost, you can restore the tracks with conducting silver paint. Good luck!
 
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primerkava

New Member
Hello
nice to meet you here

I also experienced the same thing:

- volume potentiometer works but heavy when shifted
- Bass and Treble potentiometers weigh heavily when shifted and don't work
- Potentiometer Record Level has not been tested to record but it is heavy when shifted

Are there any recommended replacement parts:
- what is the PIN of each potentiometer?
- How long is the potentiometer body length?

Thank you
 
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