sharp gf 777 pots

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bklyn sound

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What's up all... It took a old beat up 919 for me to learn how to fix 99% of the problems that bad pots cause in these old sharp's ... so what I learned I wanted to apply to my 777 that I received from my friend..

So tonight I did just that, I broke down the box to get to all the pots.. the issues were volume was scratchy at the lowest point and lost all volume at 12 position, treble would only work up until last mark - after that it would lose it . :sad: I tried deoxit in the pots twice - both times had same results but in the very beginning it did allow me to get it 75% better..

now for the treble one in particular... I have come across a few posts about these boxes not having enough brightness.. well before I did this box had those same issues, but not no more it sounds fantastic.. you can actually hear a difference bass is much stronger as well as the volume... now for the job its fairly easy to do if you know your way around these units... you really need to be careful for the wires that are attached to the pot board...

there are a 5 screws that need to come out before you can remove the pots, then they are just snapped in on the sides.. then you can kinda wiggle them out.. once you remove the pot board there are 4 tabs on back of the housing I used a tiny screwdriver to pry them up... then it will just come out be careful of the little copper washer on the back of the shaft.. once out I used deoxit to clean the little fingers off..

then I fold a little piece of sand paper to support fingers.. I then used a piece of 1000 grit to lightly sand the fingers .... use light pressure because they are delicate .. once they look all silver that's it.. I used deoxit d5 for a quick clean up.. the only 2 that require a extra step are the bass and treble. I only did the 2 small bumps on them they rub inside the drum... after that I cleaned the board that the drum attaches too...

I used a shot of the d5 and a clean microfiber towel .. I didn't spray the board I simply sprayed the towel and gently cleaned the surface making sure there was no lint from the towel.. before I reassemble I used new grease to lube them up .. once back in I bent the tabs back and that's it ...repeated the step for all six :thumbsup:

now that all the pots are clean it takes some time and patience to align the pots back in the casing they snap into the tabs but need to be aligned so the knobs wouldn't rub on the face of the box.. It's a bit of a task but the results are very rewarding in the end ... your sharp will sound like a beast again :drool: :drool: and most of your issues will be gone .. at least mine did..

next one I do I will take some pics step by step.. I'm no expert on this just wanted to share my experience with you all... thanks
 

Fatdog

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Thanks, Jimmy! I think we can follow all that. :-D
 

BoomboxLover48

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Today I was trying to take the control board out for pot cleaning per Jimmy's suggestion.

Actually my hands were shaking giggling remembering Jimmy's statement "then you can kinda wiggle them out.."

I thought... ya right! Jimmy! You are the GK King and you worked on so many of these models.

For you it will be easy and for me I am doing this for the first time and I might pull some wires out unless I know what I am doing.

It looked like a puzzle to me how to pull out the control board.

It looks very difficult when you see all the wires. Some of them are on plastic clips you can just open up to free them and leave the tied ones alone.

The right side of the board swings out clockwise looking from down to free the rest of the connecting wires.

Now I thought of posting some pics. My puppy was supervising me all the time.
 

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Beosystem10

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Nice LED conversion on Duke's eyes there! Do they cycle through all three colours when he woofs or are they single green ones?
I absolutely love dogs and yours is one very fine looking young fella. :thumbsup:

Great pics, Royce, nice and clear for beginners and old pros alike. :-)
 

BoomboxLover48

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:-D :-D :lol: :lol:

Thanks John!

Duke will be two years in Feb and we had him when he was 6 weeks. He is awesome! When I walk him people stop cars to say nice things about Duke. He is so handsome!

I was chatting with Jimmy who gave me all the motivation to take the control board out and clean it. I have a like new GF777 and this is another one where I can learn and make it work well.

Here is a pic with brown LEDs on.
 

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BoomboxLover48

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riker1068 said:
So is it the other side that has the clips to bend out and then wiggle?
You can see the 4 clips to open from the back side of each pot. The long PC board and wires with several pots attached to it is the one you need to wiggle out. :yes:
That is held by 3 or 4 screws.
 

BoomboxLover48

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Take extra care cleaning those feelers that wipes on the carbon resistance disc because it is so easy to bend them out of shape. Never use a cloth on it or it will hook on those feelers/wipers/swiping conductors.
 

stosoorok

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I'll dig up an old thread.

How do you guys clean button side little pins? PCB side is easy, but the pins require like 10x magnifying glass and are so fragile...

20150929_150117.jpg 20150929_150144.jpg
 

BoomboxLover48

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One or two stroke with a 2000 grit automotive grade emery paper along the direction of the feelers.
Be extra careful because if you come against the direction of the feelers they all will bend out of shape.
Don't press hard.
Gently glide the 2000 or 1000 grit paper along the contacting surface of those feelers.
Don't use cloth, it will catch on the feelers an twist it out of shape.

Extra extra extra careful! After that rinse off any debris with IPA and gently dry it off.

Smear Deoxit on the carbon resistance disc and install the cap with feelers.

Lube the axle if needed,
 

stosoorok

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Emery paper is a good idea, thanks! I already tried paper towels and microfiber cloth with contact cleaner really carefully but it did nothing. Also tried precision blade and got one pot quite clean.

Another interesting thing, my pot pcb outer ring is light grey and yours is dark grey. Could it be graphite coating and I cleaned it away with contact cleaner?

BTW, really nice dog you got there! :)
 

BoomboxLover48

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stosoorok said:
Emery paper is a good idea, thanks! I already tried paper towels and microfiber cloth with contact cleaner really carefully but it did nothing. Also tried precision blade and got one pot quite clean.

Another interesting thing, my pot pcb outer ring is light grey and yours is dark grey. Could it be graphite coating and I cleaned it away with contact cleaner?

BTW, really nice dog you got there! :)
I doubt contact cleaner can remove the carbon/graphite resistance layer. If only one use a sand paper it will rub off. You can check the resistance and see if it is okay. If it is open wont show any value. the color difference could be due to the pictures we took at different angles.

Lift and bring back every time you use the emery paper. One slight catch somewhere can permanently damage those feelers! Two gentle strokes would be plenty.

Thanks! He is adorable!
 

stosoorok

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BoomboxLover48 said:
I doubt contact cleaner can remove the carbon/graphite resistance layer. If only one use a sand paper it will rub off. You can check the resistance and see if it is okay. If it is open wont show any value. the color difference could be due to the pictures we took at different angles.
I don't think it's a angle/light thing, I'll check resistance tomorrow.

Picture with cleaned graphite trail and dirty :
20150929_150117.jpg

And zoom in:
20150929_150117_crop.jpg

20150929_174511.jpg

I left feelers into a contact cleaner for a night to soak! :)
20150929_174520.jpg
 

BoomboxLover48

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stosoorok

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Another job well done. My 777 sounds really good again and right channel started working again! Short description what I did:

* took all pots apart
* really good pcb cleaning with contact cleaner and paper towels
* gentle swipes with 1500 grit automotive grade emery paper along the direction of the feelers
* automotive grade silcon grease to pcb and to pot case with finger
* put all back together and a small test, everything works like new! :)

Couple pictures I took today:

20150930_112857.jpg 20150930_113315.jpg 20150930_142251.jpg
 
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