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

[Craig Heaton]

Hi Ken,

One thing to check with the Calibrator is: What frequency? Do you see a
200KC and/or a 100KC note? I had issues with the silver mica caps in my
Amelco, the Calibrator liked to oscillate at 151KC until the correct cap was
replaced. Due to the fun removing the RF section this could be a shotgun the
silver micas time.

Craig,

-----Original Message-----
From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Ken Harpur
Sent: Saturday, July 05, 2014 5:53 PM
To: R-390 at mailman.qth.net
Subject: [R-390] R-390A Noisy Ant. Trim and Raspy Calibrator

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
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