AT-1 meter fix

[Bob/WB0AUQ]

Hello AT-1 fans,

Just want to report a success story.
A few weeks back I queried the Heath List for help with the AT-1
xmtr, requesting a manual and a replacement meter as mine was
non-functional.  Well, Bud McClure/K5IUO provided a very nice
copy of the manual (thanks Bud).  Gary Harmon/K5JWK reported he
had a bum meter also and was thinking of rewinding it with some
#41 wire.  Dave Edwards/WB2TBB responded, reporting he actually
repaired his defective meter. As Dave stated, you don't have a
lot to lose if it doesn't work anyway.  So...I tore into the meter
to see what could be done (I had never actually disassembled one
before).  Could find no physical sign of the wire break but an
ohmmeter check said it was, so I started unwinding, keeping careful
notes on the number of turns.  To shorten the story, there were
several breaks, at least six, and I was over 50 turns into it so
what the heck, I removed them all, 1675 turns by my count.  The
#41 I just happened to have on hand measured a bit smaller than
the original wire so I decided to wind on a few extra turns.  Well,
1750 turns later (and no breaks), I reassembled the meter and put
power to it....10 volts thru a 1K resistor, using my Fluke 87 for
calibration.  Only had a tad over 8 ma, so apart it came.  Was able
to splice onto an end and continued winding.  Final turns was 2187
(that's what the calculator said I needed to bring up to 10 ma).
Back together and hit it with the 10 volts again...just a speck
under the 10....good enough for me.  My wind job is not near as
neat as the original but it fit back into the case and does the
job.
Hindsight tells me I could have quit unwinding after finding the
last break, only 50 turns or so was not enough to worry about but
I had no idea there were over 1600 more turns there.  All this took
several hours as I took frequent breaks to steady the nerves.  I
had benefit of working under a lighted magnifier.  Would not attempt
it otherwise.  Unwinding was easy, just circular motion with the
index finger, counting each turn, stopping each 100 and making a
mark on the notepad.  The #41 was on a small spool so rewinding was
pretty easy also, again with the index finger poking thru the spool
and a circular motion, letting the finger provide tension, stopping
every 100 turns to jot down a mark.  The small wire is actually
pretty tough, just don't sneeze when you have tension on it.
The AT-1 is back on the air with a whopping 12 watts out.  After
tune up I put the meter switch in center so it is out of circuit.
No sense in it bouncing all over the place....and I don't want to
rewind that coil again anytime soon.
Good luck to anyone repairing their AT-1 (or any other) meter.

73,
Bob/WB0AUQ      brainbol at lawrence.ks.us

--- --- --- --- --- --- --- --- --- --- --- --- --- --
To subscribe: listserv at listserv.tempe.gov
and in body: subscribe HEATH yourfirstname yourlastname
To unsubscribe:  listserv at listserv.tempe.gov
and in body: signoff HEATH
Archives for HEATH: http://www.tempe.gov/archives
--- --- --- --- --- --- --- --- --- --- --- --- --- --