|[AMRadio] R-390A Help|
w3slk at verizon.net
w3slk at verizon.net
Mon Jul 7 18:59:35 EDT 2014
I'm not much of a 390A guy but I have worked on mine. First thing would
be to check the input line filter. It is a small square little metal box
type set up that is fastened to the upper rear bulkhead of the receiver. I
had mine go out and I just removed it. The Navy used tons of the R-390A's
because they were impervious to interference from shipboard radars. Thus the
reason for the filter. You don't need it unless your antenna systems is so
unbalanced you are getting into your powerline.
From: Bill Guyger via AMRadio
Sent: Monday, July 7, 2014 6:45 PM
To: Discussion of AM Radio in the Amateur Service
Subject: [AMRadio] R-390A Help
I acquired a 390A over the weekend from a friend who can no longer see to
work on his gear. He made me promise to not sell it or trade it while he was
still alive which I wouldn't do anyway out of respect to a genuine
gentleman, a fine ham and one hell of a builder of radio related gear.
Returning it to the air is my way of honoring a long time friend.
The last time he fired it up the line fuse blew preceded by a sound like one
might experience after too much Mexican food and a wisp of smoke. He
suggested something in the power supply which seems pretty basic other than
Collins' use of 26Z5's for rectifiers. There's not much else there except
for chokes and a couple of caps which date from the 1960's.
I haven't had time to really dig into the unit, and those old caps seem a
logical place to start in addition to suspecting one of the rectifiers.
Hopefully lightning etc. didn't get into the radio and fry something when he
My question to some of you R-390 gurus out there is. Is there a history of
Power Supply issues and does anyone know of a source of 26Z5's. Or....if
it's not heresy could I replace them with Silicon rectifiers after doing
something about the additional B+ that will create? Not sure I want to
pillage a great radio by doing that anyway if I can find the correct tubes
but it's a consideration.
Many thanks and 73 Bill AD5OL
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