Re: {Collins} 51S-1 PTO Issues



Just curious if you actually measured R-62 as 100 Ω, or, is it possible that
a 1kΩ resistor got hot enough to discolor the red band, making it LOOK
brown?

Also, in a curious vein, does your early S/N radio have a round emblem PTO?
More than likely it does, as most of the early two tube PTO's which would
may have been an original on a three digit S/N radio.

And yes, that PTO output transformer is not critical.  Just get a small
toroid and wind one yourself.
I'll see if I can dig up the specs because I have had to do that at least
once.
If I remember correctly, it was around a 5:1 Z ratio, but that was a long
time ago.
Agreed, it is a very unlikely part to fail. 

73, Charlie k3ICH





-----Original Message-----
From: Collins [mailto:collins-bounces+pincon=erols.com@xxxxxxxxxxxxx] On
Behalf Of thoyer via Collins
Sent: Sunday, October 01, 2017 9:42 PM
To: collins@xxxxxxxxxxxxx
Subject: {Collins} 51S-1 PTO Issues

Working on bringing SN 131 back to life. Found PTO not PTO-ing.........
 
External to the PTO someone at one time replaced R62 with a 100 ohm
resistor, schematic calls for 1k. So far this is the only area of rework I
have found.
 
Resistance measurements on V15 pins 5 and 6 were not making sense. Pulled
PTO out and found R504 was fried and R503 measured 77k - should be closer to
56k.
 
Measuring between pins 1 and 4 of T503 shows 33m - basically open. Caps C507
and C508 are not shorted.
 
Bottom line, I can replace all of the parts to bring things back in spec
BUT, what about T501? Anyone know of a source for these?
 
Thanks, 
 
Tom
W3TA
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