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
If the above message appears, it came from Steve's Son of Laptop!
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