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| General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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3rd Jan 2022, 1:19 pm
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#1 |
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Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,762
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Strange readings on a ganged potentiometer
I am working on a 30s hmv radiogram , decided to take the vol / rf gain pot apart as both read oc ,anyone seen anything like this, Mick.
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3rd Jan 2022, 1:34 pm
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#2 |
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Guest
Posts: n/a
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Re: Strange readings on a ganged potentiometer
Is it a capacitive coupling? Could work for RF.
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3rd Jan 2022, 1:38 pm
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#3 |
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Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,762
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Re: Strange readings on a ganged potentiometer
The circuit shows two normal pots !the volume control for radio varies the screen volts on the rf stage earthy end , Mick.
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3rd Jan 2022, 2:32 pm
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#4 |
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Guest
Posts: n/a
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Re: Strange readings on a ganged potentiometer
Looks like very log pots, try an ordinary one first. My Cossor 234 has a rheostat in the first valve (a screened grid job) filament supply for RF gain. Doing that obviated the HT (all three of them) switches.
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3rd Jan 2022, 2:35 pm
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#5 |
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Guest
Posts: n/a
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Re: Strange readings on a ganged potentiometer
Another thought, is the top plate pushed down onto the track by the "wiper"? Minimal track wear but a dodgy contact after years.
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3rd Jan 2022, 3:09 pm
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#6 |
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Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,762
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Re: Strange readings on a ganged potentiometer
Hi thanks for that , I have just fitted a 50k/50k seems to work ok ,the reason I checked the volume control for the pick up is I had motor boating when three quarters vol , thought about conducive paint ,Mick.
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3rd Jan 2022, 3:35 pm
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#7 | |
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Guest
Posts: n/a
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Re: Strange readings on a ganged potentiometer
Quote:
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