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Scratchy volume pot only when turn power ON or OFF
Scratchy volume pot only when turn power ON or OFF
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Old 18th May 2018, 05:36 PM   #11
Mooly is offline Mooly  United Kingdom
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Scratchy volume pot only when turn power ON or OFF
I'm saying that it wouldn't surprise me if the problem was the pot. Having looked at the circuit I would suspect the pot even more...

This is the volume control, and the cap that connects to the wiper of the control is drawn as a non polarised type (so not an electrolytic). 220k pF is 220,000 pF which is more commonly written as 0.22uF
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Old 18th May 2018, 05:40 PM   #12
YanKleber is offline YanKleber
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Originally Posted by Mooly View Post
I'm saying that it wouldn't surprise me if the problem was the pot. Having looked at the circuit I would suspect the pot even more...

This is the volume control, and the cap that connects to the wiper of the control is drawn as a non polarised type (so not an electrolytic). 220k pF is 220,000 pF which is more commonly written as 0.22uF
So and sorry for my ignorance as I am not a tech in your opinion the best shot at this moment would be simply replace the pot?
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Old 18th May 2018, 05:43 PM   #13
Mooly is offline Mooly  United Kingdom
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Scratchy volume pot only when turn power ON or OFF
The pot is the most likely suspect to me but I wouldn't give you a 100% guarantee without having on the bench in front of me such that I could do other tests and make a more informed judgement. However experience says 'pot'.

Is it of a type that can be cleaned... has it got openings in it or is it all sealed ?
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Old 18th May 2018, 05:50 PM   #14
YanKleber is offline YanKleber
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Originally Posted by Mooly View Post
The pot is the most likely suspect to me but I wouldn't give you a 100% guarantee without having on the bench in front of me such that I could do other tests and make a more informed judgement. However experience says 'pot'.
I got it!

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Is it of a type that can be cleaned... has it got openings in it or is it all sealed ?
I still didn't remove the cover to look inside. Will do this in the next few days and will get back with further info.

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Old 18th May 2018, 05:52 PM   #15
Mooly is offline Mooly  United Kingdom
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Scratchy volume pot only when turn power ON or OFF
OK
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Old 18th May 2018, 05:53 PM   #16
YanKleber is offline YanKleber
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OK
And thank you very much so far!
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Old 18th May 2018, 05:58 PM   #17
thimios is offline thimios  Greece
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And thank you very much so far!
Don't expect from an old pot not to be fault.
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Old 18th May 2018, 06:10 PM   #18
Ian Finch is offline Ian Finch  Australia
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The 166 schematic I'm reading, shows a 1uF electrolytic where the film cap is - it might be worth checking which schematic and which type of cap. applies to the amplifier you have.

A tapped volume pot, as it appears to be for a the loudness function, isn't an easy item to find, since loudness controls were phased out long ago. I suggest first trying to source a tapped, dual 100k ohm volume pot (i.e a log. or audio taper pot.) before trying to remove it.

You can identify tapped pots as having 4 pins instead of 3 for each potentiometer section, or 8 pins in total here. The next problem is to determine whether any pot. you may find will fit the PCB correctly, with suitable pin spacing. If the pot is not fitted to the PCB on your version, so much the better.
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Last edited by Ian Finch; 18th May 2018 at 06:12 PM.
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Old 18th May 2018, 06:30 PM   #19
mchambin is offline mchambin  France
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To know wether it is the pot or not, I would consider swapping the pots between the two channels.
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Old 18th May 2018, 06:34 PM   #20
mchambin is offline mchambin  France
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To know wether it is the pot or not, I would consider swapping the pots between the two channels.
Or may be just the wiper connections by lifting
at the caps.
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