[R-390] C227 in R390A

[Drew P. via R-390]

Message: 5
Date: Thu, 4 Dec 2014 12:42:31 -0600
From: <ngietz at mymts.net>
To: <r-390 at mailman.qth.net>
Subject: [R-390] C227 in R390A
Message-ID: <BLU179-DS243198A88B1913B82777BDE780 at phx.gbl>
Content-Type: text/plain; charset="utf-8"

Nelson Gietz wrote:

"Greetings all... I have a 1963 vintage R390A that I?m going through.
Right now, the RF section is getting attention.  But I?m wondering
whether C227, the stud mounted cap on the RF deck should be
replaced.  I usually terminate and replace all paper caps without
prejudice in vintage electronics, but I believe this one is an oil-
filled cap and may be more reliable than the brown beauties and
their waxy cousins."

C227 is a cathode bypass for the RF amplifier stage. I've had this cap fail once.  Symptom was loud popping noises in the receiver's audio as the antenna trimmer control was operated, pointing to oscillation of the RF amplifier stage. DC voltage at this circuit point is relatively low, and so metalized film cap should work fine.

Drew