Yeah, I was expecting to find a bad power supply. The odds of this are
about that of getting a winning scratch ticket (which is why I avoid them).
I'll dig out a box tomorrow and get it to the PO. At the least, you can get
some nicer pics of it. I really want to finish the A so I can start on the
R-4B - which works fine by itself but doesn't play well with the T-4X due to
all of its jacks being "hi-jacked" for some higher AM purpose ;-) It's also
going to need a bath, big-time.
73,
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!
----- Original Message -----
From: "Garey Barrell" <[email protected]>
To: "Steve Wedge" <[email protected]>; "drakelist"
<[email protected]>
Sent: Wednesday, August 24, 2011 9:46 PM
Subject: Re: [Drakelist] Well, it looks like both PTO's DO have issues.
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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