[R-390] R-390A Noisy Ant. Trim and Raspy Calibrator

[Ken Harpur]

Hi Group,

I have two issues I'm trying to resolve. A very scratchy/noisy Antenna trimmer on a Teledyne R-390A. The RF Deck has been completely disassembled and cleaned including the shaft and it's related components that protrudes through the front panel. The noise is mostly audible on the lower bands and it's not a quiet, distant noise, it's very loud. The noise is not audible on bands above 16 Mhz.

So...Is there a way to disassemble/clean the Antenna trimmer to clean it? It looks like the small pin at the top has to come out to remove the cover and gain access to the innards. 

My second issue is on an EAC model. The Calibrator is very raspy (dirty) sounding, not the nicer, more sine-wave like sound from the Teledyne. Work in this area has been limited to visual inspection and re-doing potential cold solder joints. The crystal oven has been swapped over from the Teledyne with no difference...still raspy and the EAC crystal oven put in the Teledyne and the note is clean, so I'm sure it is not the Crystal oven. V-205 and V-206 have been replaced...nope, still raspy. Of note is when I wiggle V-205 the pitch of the note changes slightly (this does not happen on the Teledyne) so I re-soldered all tube socket pins...no change. I suspect I have a bad mica in this area. All resistors are within spec and so far no components have been replaced in this deck.

Any ideas or advice would be much appreciated!

Kind regards,
Ken Harpur
ZL3AA