[R-390] R-390 Antenna Relay Chatter

[David Wise]

Should not chatter.  #1 suspect is CR801; selenium rectifiers have a notorious habit of increasing forward resistance as they age.  Convert to silicon plus a resistor in series to mimic the natural forward resistance of new selenium.  (I don't know what that value should be.)  This is what Tektronix did with their oscilloscopes; for every selenium-powered model, they created a silicon retrofit kit.  One of my scopes has one.

Or you can add a reservoir capacitor, starting small and increasing until the chatter is reliably gone at low mains voltage.  I am using 100uF.  Upside is potentially reduced hum.  Downside is that CR801 will continue to deteriorate, so eventually the problem will recur.

HTH,
Dave Wise
SWL (inactive)
________________________________
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Barry <n4buq at knology.net>
Sent: Friday, October 7, 2022 9:59 AM
To: R-390 Mailing List <r-390 at mailman.qth.net>
Subject: [R-390] R-390 Antenna Relay Chatter

When in STANDBY, the antenna relay in my R-390 produces a bit of chatter.  Is this normal?  I see where that relay is fed, unfiltered, from CR801 which, from the pictures in the manual, appear to be a stack of selenium diodes and I'm wondering if that rectifier stack might be a problem.  Anyone know what to expect from that relay in STANDBY and, perhaps, what I'm seeing might be normal?

Thanks,
Barry - N4BUQ
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