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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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8th Jun 2020, 9:29 pm | #1 |
Pentode
Join Date: Apr 2018
Location: Canterbury, Kent, UK.
Posts: 189
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Freeing off a Jackson C804 variable capacitor
I'm using a Jackson C804 capacitor for the main tuning in a simple receiver
http://www.royalsignals.org.uk/jackson_bros_caps/c8.htm Yes, I know I should have used a proper double ball race variable capacitor but I didn't have one in the drawer. It seems stable enough when I thump the radio but really it's a bit too stable in as much as the shaft needs more turning torque than I'd like. As far as I can see the bush isn't adjustable. Before I try applying some watch oil with a pointed matchstick and perhaps afterwards regret it, has anyone tried lubricating this type of non-ballrace capacitor to make it turn a little bit more freely? Thanks, Alan |
8th Jun 2020, 9:39 pm | #2 |
Nonode
Join Date: May 2007
Location: Preston, Lancashire, UK.
Posts: 2,511
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Re: Freeing off a Jackson C804 variable capacitor
As a trimmer it was probably designed to be stiff to avoid inadvertent movement.
Andy |
8th Jun 2020, 11:33 pm | #3 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,934
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Re: Freeing off a Jackson C804 variable capacitor
Although the catalogue calls them all "trimmers", clearly, the ones which can accept a knob may be used as front panel controls. I don't think I've previously encountered one that was a problem. I cannot see why a trace of lubricant should be an issue; maybe the silver plating will show some tarnish but many of the old ones do anyway.
B
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9th Jun 2020, 8:53 am | #4 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Freeing off a Jackson C804 variable capacitor
Give it graphite instead of oil first?
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14th Jun 2020, 8:59 pm | #5 |
Pentode
Join Date: Apr 2018
Location: Canterbury, Kent, UK.
Posts: 189
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Re: Freeing off a Jackson C804 variable capacitor
Applying lubrication didn't help.
There is a spring clip at the back of the ceramic insulation that carries the earth tag but also pulls the rotor assembly into the bush on the front. A (very) gentle tweak with a pointed stick to slightly bend the clip and reduce the clamping pressure has solved my problem. Yes it's a one way street but a series of small tweaks while checking the required torque until it turned freely but with no end play gave me the desired result. 73, Alan G3XAQ |