[R-390] new member, R390A, no signal when first powered on, works after 10min but RF cutting in and out

[Craig Heaton]

Hello Pat,

Seems like time to break out the signal generator and o'scope. Follow the signal thru the stages till it disappears. Darned popping noises can come from many sources, bad grounds on tube sockets, dirty pins on tubes, dirty pins on RF or variable IF cans, etc.

Craig, 

-----Original Message-----
From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of weekspat at imonmail.com
Sent: Thursday, June 26, 2014 12:14 PM
To: r-390 at mailman.qth.net
Subject: [R-390] new member, R390A, no signal when first powered on, works after 10min but RF cutting in and out

Hi,

I got a Motorola R390A, signal corps unit last year.  Have recapped, and fixed most problems, but I've got one nasty intermittent one.
 Seems like the RF signal is not getting to the RF AMP and or conveter or thru it, so I think I've got no signal to the IF section.
 Then after some time it starts making some popping sounds and shortly after that "pops" on with normal reception.  Happens on all bands.  I'm wondering if those mini BNCs are to blame.  Any hints ?
 The problem sort of " comes and goes" so its hard to nail down thanks, Pat Weeks ______________________________________________________________
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