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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 10th Aug 2018, 7:59 pm   #61
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Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: IF fault on Eddystone 770R

As I mentioned before, the Americans were fond of building the IF's tuning capacitors into the mounting plates that supported the wire connections. So at a quick glance it looks like there are no tuning capacitors present. It was a good move to replace them in your IF's.

Another topic raised here is what happens to either mica-plate tuning capacitors or other types that are not sealed to liquids, for example ceramic types too.

If a cleaning agent is sprayed on them, it transiently alters their capacitance (due to the dielectric constant of the solvent) until it evaporates. For example, while WD-40 is compatible with practically every component, If it gets into mica tuning caps or many types of adjustable capacitors it drastically increases the capacitance and also, the value fluctuates and it takes a long time to evaporate.

This is why WD-40 should never go anywhere near scope attenuators where there are small adjustable capacitors, or say the tuning capacitors on any IF transformers, or even the types built into the wafers on the IF transformers in the ones you have. It could get there, for example, if WD-40 is used to loosen the slugs, which has been a recommended technique, but it falls over if there are any non liquid proof capacitors it can get into.
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