[AMRadio] R-388 PTO info needed

John Coleman ARS WA5BXO wa5bxo2005 at pctechref.com
Sun Dec 25 21:14:49 EST 2005

I have had one in and out of a 32V3 XMTR several times repairing flood
damage.  It's not that hard.  The oscillator circuit is not that
complicated.  I don't know the same about the 75A4 PTO removal, but if
that is not to bad, then just fined the open resistor or the shorted
capacitor and replace it.  Be sure to check the DC and filament lines
going into it first.  Mine was filled with mud and had a stuck slug,
which I broke trying to free it up.  But I got it working.  Of course
the calibration is way off because of the broken slug, but that is not
going to happen in your case.  Yours was not full of mud for 2 - 3


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of John Lawson
Sent: Sunday, December 25, 2005 3:47 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] R-388 PTO info needed

   Further to my Xmas Eve Scrooge Radio Post - I have discovered that no

signals of any kind appear on the PTO output cable when isolated from
mixer tube, and injecting the correct frequency into that pin of the
(from my bench oscillator) restores the radio to operation.

  So, of course, the PTO has quit, and the tubes (AFAIK) are good - but 
next I'll replace them with a couple that test out at better than 70% Gm
somehow I think that's not going to be the Problem.

   If anyone within the sound of my keyboard has any experience actually

repairing this series of PTO - it's a Collins 70E-15 ser. M1751 - I'm 
trying to guage whether I should spend the time to dredge it out and fix

it - or (since the front panel needs to be refinished) I would be better

served by just bundling it off to someone and letting an expert refurb
radio. I do plan to keep it, it's my Fave Reciever - for Ham and SWL -

  Also: if you have a quote to perform the above, lemme know ASAP - I'm 
'motivated' as they say in Real Estate.

  Cheers and Best of the Season!

John  KB6SCO
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