[R-390] Crystal Osc Deck Trimmer Failure

[2002tii]

>I would surmise that Collins never anticipated that these radios 
>would still be in service nearly 50 years later, and hadn't 
>considered that in that time the silver plating could slowly migrate 
>through the trimmers' dielectric (at least I think that would be the 
>failure mode).

Much more likely that it was accumulated dust, dirt, and atmospheric 
pollutants, which caused a leakage path.  I always clean these 
trimmer caps with solvent whenever I have a radio apart (Freon is 
best if you have a stash...).

Best regards,

Don