On Dec 27, 6:48*pm, JS wrote:
Good documentation. I assume the altimeter was reading normally, so no
icebergs in the lines.
* Andy , do any other aircraft on your field have an ACK on board? If
so, try hooking your encoder to another transponder (one connector and
you won't even need to move the hose for this test). It will probably
do the same thing.
* The tech who certified my transponder installation referred to the
A-30 as a "disposable" encoder. They're cheap, and easy enough to
change. You could spend more on repairing the old one.
Jim

The results provided are for a bench test of the encoder with the
static port vented to ambient pressure. There was no aircraft,
altimeter, or transponder involved. I designed the test box so it
could be inserted both "in- line", and to interface with the encoder
alone. My first test was on the aircraft as I wanted to see how the
installed system behaved. Once I knew it behaved the same with or
without the transponder in circuit I knew the problem was the encoder,
not the wiring or the transponder. I then moved to the comfort of my
living room instead of working on the aircraft floor.

After the first test results were posted I did additional testing with
a fridge cold soak (less severe than freezer) and also a room
temperature soak. For the fridge test, soak at +37 deg F, it took 40
minutes to stabilizes at correct altitude. For the room temperature
soak (67 deg F) it still took over 30 minutes from power on to
stabilize at the correct altitude. Only an engineer would understand
the quest for data

I can replace the A-30 for $150 + shipping but I think it can be
repaired for under half that. Maybe I'll do both.

Andy