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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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20th Feb 2018, 12:28 pm | #1 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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1924 tuning capacitor strange reading
Checking this tuning capacitor , which is clearly marked .0005uf only reads max 270pf . I have stripped it it was all gunged up with grease. gave it a good clean removed one layer of mica which was disintegrating, still only reads 270 max , has anyone had dealings with this type of capacitor?. Mick.
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20th Feb 2018, 12:55 pm | #2 |
No Longer a Member
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
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Re: 1924 tuning capacitor strange reading
I wonder if the original grease was acting a a dielectric and increasing the electrical capacity.
If that was the case, once you have cleaned all the old grease out, you could try adding new grease. Probably the microscopic surfaces of the remaining mica sheets are impregnated with hydrocarbon based grease that was on it originally, so silicone grease would be a bad choice. You could try re-greasing it with automotive bearing grease. Of course there could be other explanations for the loss of capacity. |
20th Feb 2018, 1:13 pm | #3 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
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Re: 1924 tuning capacitor strange reading
I thought about that, unless something as happened to the original grease, causing low capacitance. Just checked the other capacitor it reads low just the same! Just about to check the meter with a fixed cap.
Cheers, Mick. |
20th Feb 2018, 2:16 pm | #4 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
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Re: 1924 tuning capacitor strange reading
Hi Looks like Argus 25 was on the right path I plastered both sides of the rotor with the only car grease I have Ovoline 85 ep2 means nothing to me , but it has increased the reading to 340pf Is there a known grease to use ? Mick.
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