Steve -
Please don't be offended, but I find it _EXTREMELY_ hard to believe that you have just happened
upon TWO bad PTOs out of TWO. We're overlooking something here, but I just don't buy it, based on
45 years of owning and working on 4 Line gear and coming across less than a half-dozen ones with
'problems', and those were fixable.
I know you're tired of messing with them, and understand completely. Please send either one down
here and let me dig into it. Perhaps you've found the 'missing link', but I don't think so!! :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Steve Wedge wrote:
UUT #1: PTO from T-4XB, mounted in R-4A. R-4A when using its own PTO gets chirpy/unstable signals
after warm-up.
UUT #2: Original PTO from R-4A, out of the rig.
Power:
Internal receiver power
Station power supply (30A linear), turned down to 11.1V
monitor: Elecraft K3 tuned to 4917 kHz (approx) with series 10 dB pad and x10
scope probe.
Test setup #1:
UUT #1 connected to power buss from 0B2 and normal chassis ground. Signal output open except for
test equipment. Connected to monitor. Warmed up approximately 25 minutes, signal became
unstable. Turned R-4A OFF and immediately connected station supply. Instability would not
immediately resume. Long-term, frequency would jump and occasionally chirp.
Disconnected remainder of the 11V buss in the receiver from the PTO so that station supply was
powering only PTO. After a period of time, instability returned. receiver was off.
Conclusion: UUT#1 (the T-4XB FET PTO) is the source of the unstable signals.
Test setup #2:
UUT #2 connected to station power supply and monitor same as #1. After about 30 minutes, signal
was shifting but not as bad as #1.
Conclusion: UUT #2 also is unstable.
I need to find a counter now so that I can determine the frequency with the cover removed. From
that point, I can try stressing individual parts.
Garey, I may still send the older PTO to you and you can document it.
This receiver is worth spending the time on as it came out my refurbishment looking and otherwise
sounding very good. Cosmetically, it's about an 8 / 10 with some brown spots on the chassis and
small scratches on the cabinet.
Thanks to all for feeding me ideas. This has been fun but I want to finish ;-)
Steve Wedge, W1ES/4
"I can't complain, but sometimes I still do."
- Joe Walsh
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