Steve -
OK. I fashioned a 'sorta' fiducial out of a piece of wire and an alligator clip to the gearbox.
Allowing for parallax, lighting, reflections, 'reading' glasses, and just plain poor close-up
vision, it looks to be within a few hundred Hz at each 100 kHz marker, and about 1.5 kHz from end to
end. Well within original specs. Of course, with no Rubidium standard I don't 'really' know where
it is, but I think it's 'CEAPP' or 'Close Enough for All Practical Purposes'.!
I'm sure the tubular cap had some 'secret' specification that we'll never know, but the little
Dur-Mica seems to be holding up just fine. Nothing else has been changed, and aside from about a
115 Hz swing from A/C breeze soak to room temp soak doesn't seem excessive to me. I suspect nicely
bolted down to a chassis inside a nice warm receiver or transmitter it will be just fine.
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:
I am with Garey, though, in that I'm still finding it hard to believe that
there are problems with
both. That would be like getting struck by lightning twice.
I'm still having a hard time thinking it's the supply, as that 0B2 should
regulate its output at -
what is it? - 108V? That gets dropped through the big WW resistor and ends up
as approximately 10
- 12V, which gets dropped by the Zener inside the PTO. To my thinking, even if
the 108V were to
sag a little, as long as the voltage is above the Zener point, it shouldn't
matter as long as
there's sufficient current.
Both PTO assemblies - when in the R-4A - seem to be very touchy.
W1ES
-----Original Message-----
From: Bill Frost
Sent: Aug 25, 2011 10:06 AM
To: Steve Wedge
Cc: Garey Barrell
Subject: Re: [Drakelist] Well, it looks like both PTO's DO have issues.
Hello Steve,
OK, Great, it will be interesting to see what Garey finds.
73, Bill
----------------------------------------------------------------------------------------------------
*From:* Steve Wedge <[email protected]>
*To:* Bill Frost <[email protected]>
*Cc:* Garey Barrell <[email protected]>
*Sent:* Thursday, August 25, 2011 9:55 AM
*Subject:* Re: [Drakelist] Well, it looks like both PTO's DO have issues.
Cover was on each during the tests. Tried running it with cover off to try
and poke at
components to provoke them ;-) Of course, I'd have to rig up some way of
holding the yoke down.
I'm actually going to send the older one to Garey tomorrow to get a fresh
set of eyes (and a
better-stocked parts bin) on it.
73
W1ES
-----Original Message-----
From: Bill Frost
Sent: Aug 25, 2011 8:21 AM
To: Steve Wedge
Cc: Garey Barrell
Subject: Re: [Drakelist] Well, it looks like both PTO's DO have issues.
Hello Steve,
If you preformed the tests with the PTO cover removed, not a good test,
you must have the
PTO yoke spring pulled and clipped to the back of the coil form or ???
Allowing the
yoke/slider bar to ride free is not a good test as the PTO will always
chirp or drift
around without tension on the yoke/slider bar. It's best to leave the
cover on and spring
engaged during any test of the PTO assembly.
73, Bill
----------------------------------------------------------------------------------------------------
*From:* Steve Wedge <[email protected]>
*To:* [email protected]
*Sent:* Wednesday, August 24, 2011 9:16 PM
*Subject:* [Drakelist] Well, it looks like both PTO's DO have issues.
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
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