[AMRadio] R-390A Help


Jay Bromley jayw5jay at cox.net
Mon Jul 7 21:33:56 EDT 2014


Be sure to have a close look at the ballast tube.  73 de w5jay/jay..

-----Original Message-----
From: AMRadio [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Bill
Guyger via AMRadio
Sent: Monday, July 07, 2014 5:46 PM
To: Discussion of AM Radio in the Amateur Service
Subject: [AMRadio] R-390A Help

Hi All

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
wasn't looking.

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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