Sharp GF-555 Volume Slider Advise !

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onx309

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Can anyone give me some advise as my lad's Sharp GF-555's volume slider has stopped working all together so no sound now, have used spray to clean it & even desoldered it & pulled it out dismantelled it cleaned up tracks and contacts everything relubed still nothing it's dead as a door nail. What I was wondering was if the Mic fader control is essentially the same part, from looking at the service manual parts list although they have different part numbers by 1 digit they are both 20K ohm. Or does anyone know of a replacement slider potentiometer parts number etc, any help would be gr8 as he's doin' my head in keeps asking me (when U gonna fix It) he's starting to get on my nerves just want to get him of my back a.s.a.p.
 

Beosystem10

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Feb 21, 2013
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I had a quick look at the circuit diagram and it appears that the sliders aren't the same. The mic mixing control is linear where the volume control is logarithmic. This is from the original information in the factory service book, the one that's parked at HFE differs in several ways so I've followed the original whenever I've had to do anything to mine. As it happens, I have the back off as I managed to get a new screening panel for the back cover (the terminal broke off and she'd been humming for a while) and am busy with that, my DMM confirms the difference, as the reading on the mixing control varies by the same amount as the travel does.
 

Beosystem10

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I've found CTS inside some Sharps, a mixture of brands in others so I'd hazard a guess that Sharp were no different from the rest of the field back in the day, placing their orders with whichever supplier they could squeeze the hardest on the price.

The sliders in my own 555 appear to be of various makes yet none has ever been replaced, hence my saying the above.
 

Superduper

Member (SA)
Originals wouldn't be available anymore. Are you sure the slider is bad? You were able to remove it successfully, which is no small feat. I imagine you are able to test them out of circuit to confirm they are bad?

Not sure how much it is worth to you to get that 555 repaired but being in the UK, you might be able to save some money by getting a UK member to help. Maybe try PM Docs?

I can rebuild them if you like for a small fee, but given back/forth from UK to USA would add significantly time and cost wise.
 

Beosystem10

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Originals wouldn't be available anymore.
Yes, they would. :-) Either brand in an Optonica-labelled poly bag pukka, unopened and as new from Cullercoats aerial services or High Bridge PA spares, either no more than 70 miles for me. However, I've had a few through as well as my own ones in the last two years alone and have yet to find one with a slider that's failed totally. They've been as over engineered as the rest of these massively thick boxes.
Just saying though but, and there's always the outside chance.
 

Superduper

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Beosystem10 said:
Yes, they would.
That's news to me. I've never been able to find any OEM part such as these for sale from any source, so if you have a bonifide source that you can check and confirm, I'm sure the OP would be very grateful to you if you can provide him with the information he needs to get them from your source. The replacement part from Sharp is RVR-Q0069AFZZ. If you find a generic replacement, keep in mind that the knob shafts will likely be different. It might be longer, shorter, thicker, different taper (physical, not elec curve). Also the mounting legs could be different. On the JVC's, their OEM'd ones have stepped legs to fit the mounting holes. The generic Alps have slightly different leg mount, and would not go in proper. I'm just relaying my experience. The large parts clearinghouses such as partstore, UED and encompass sometimes show them available. They'll take your order, your money, and after 3-6 weeks, cancel and refund your money saying no longer available. A quick google of the part# & I get this:
http://www.encompassparts.com/item/3913162/Sharp/RVR-Q0069AFZZ/Variable_Resistor



Beosystem10 said:
................. have yet to find one with a slider that's failed totally. They've been as over engineered as the rest of these massively thick boxes.............
That is completely 180 degree from my own experience. I've rebuilt so many for myself and other members I've lost count ages ago. The reason I asked whether the slider was an Alps branded one or not is because these Alps sliders are specifically of poor quality. I know this for a fact because I have a bunch of NOS Alps sliders I snapped up specifically to sacrifice the innards to rebuild these sliders. I have seen significant number of these DOA (feelers broken off) right out of the box. If yours were trouble free, then that's great for you. But ask members who own the JVC M70 and RC-838 (both use these dang Alps sliders) and you'll find many with problematic sliders. In fact, just search the Boomboxery archives regarding jvc alps sliders and examples of broken sliders are plenty enough.
 
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