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jfosse1(at)shawneelink.ne Guest
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Posted: Sat Feb 18, 2006 8:58 pm Post subject: Queer Electrons In N329F |
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Listers. I have a weird problem. I have the LED indicator for the
elevator trim on my 701. Everything works perfectly until I key the
comm radio mic. When I key the mic, with intercom on or off, the LED
drops from the neutral position to the bottom of the indicator. I
have checked grounds, antenna isolation and everything else I can
think of, with no success. I am using the ICOM A200 and a Flight Tech
intercom. Any ideas out there?
Jim Fosse
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craig(at)craigandjean.com Guest
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Posted: Sat Feb 18, 2006 10:18 pm Post subject: Queer Electrons In N329F |
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I see two possibilities: either something is drooping in the electrical
circuit or the indicator itself has enough sensitivity to pick-up the RF. So
measure across these points while keying the radio off and on:
Power leads to the indicator (red, black)
Leads from the servo to the indicator (blue, green, orange) to ground
(black)
If you don't see a change then the indicator is picking up RF either through
the wires or the air. You can try blocking any RF passing through the wires
by adding a ceramic capacitor from each of the four non-ground leads to
ground. Or, if you can lay your hands on a ferrite core, pass the wires
through that close to the indicator. A ferrite core is what is inside of the
blobs on the ends of some of the cables running to or from your computer.
You can get one at Radio Shack (Part number 273-105):
http://tinyurl.com/ajvmd
What happens if the antenna lead isn't plugged to the back of the radio?
You could also ask your question on the AeroElectric list on the Matronics
server (just like this one).
WARNING: I am not an electrical engineer although I do talk like one.
-- Craig
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p.mulwitz(at)worldnet.att Guest
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Posted: Sat Feb 18, 2006 10:52 pm Post subject: Queer Electrons In N329F |
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Hi Jim,
I just had a gut reaction to your LED problem. Perhaps the RF
energy is finding its way to the led circuits in the
indicator. Perhaps some shielding (grounded) around the LED would
help. If that doesn't do it, you might need to install coax
(shielded cable) between the LED indicator and the trim tab servo.
It might be a lot simpler to replace the LED indicator with the
needle (volt meter?) one. Perhaps a call to the vendor would have
them sending you the alternate indicator or supplying a more
intelligent idea of the problem.
Good luck,
Paul
XL wings
Quote: | Listers. I have a weird problem. I have the LED indicator for the
elevator trim on my 701. Everything works perfectly until I key the
comm radio mic. When I key the mic, with intercom on or off, the LED
drops from the neutral position to the bottom of the indicator. I
have checked grounds, antenna isolation and everything else I can
think of, with no success. I am using the ICOM A200 and a Flight Tech
intercom. Any ideas out there?
Jim Fosse
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p.mulwitz(at)worldnet.att Guest
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Posted: Sun Feb 19, 2006 2:55 am Post subject: Queer Electrons In N329F |
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Keying a transmitter without an antenna attached is likely to destroy
the transmitter. The correct way to do this test is to attach the
transmitter to a dummy load - a high power resistor usually cooled by
a gallon of oil.
Perhaps a simpler way to test this theory is to use a portable comm
transmitter either attached to the same antenna or transmit near the
same antenna and see if this has an impact on the LED indicator.
If you want to try the ceramic capacitor trick, install the caps at
the same end of the servo wires as the indicator.
Good luck,
Paul
WARNING - I used to be an electrical engineer - now I am just a bum.
Quote: | What happens if the antenna lead isn't plugged to the back of the radio?
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gfmjr_20(at)hotmail.com Guest
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Posted: Sun Feb 19, 2006 3:14 pm Post subject: Queer Electrons In N329F |
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Jim--
You may be aware of this but just in case-----the led indicator position
will
be at the bottom without any input from the servo. The only leds are the
orange,green and blue wires. These deliver the centering, up and down
indications.
If your servo is losing power, threrfore no output, the led will indicate at
the
bottom. I'd check the white wires that supply power to the servo.
You possibly have a short or mechanical interference between the PTT
and servo switches.
My best guess
George May
601XL 912s
Quote: | From: "Jim Fosse" <jfosse1(at)shawneelink.net>
Reply-To: zenith-list(at)matronics.com
To: "Zenith List" <zenith-list(at)matronics.com>
Subject: Queer Electrons In N329F
Date: Sat, 18 Feb 2006 22:16:09 -0600
Listers. I have a weird problem. I have the LED indicator for the
elevator trim on my 701. Everything works perfectly until I key the
comm radio mic. When I key the mic, with intercom on or off, the LED
drops from the neutral position to the bottom of the indicator. I
have checked grounds, antenna isolation and everything else I can
think of, with no success. I am using the ICOM A200 and a Flight Tech
intercom. Any ideas out there?
Jim Fosse
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btucke73(at)yahoo.com Guest
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Posted: Sun Feb 19, 2006 7:43 pm Post subject: Queer Electrons In N329F |
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Jim,
I have the same problem in my 601. My trim cable
is routed together with my antenna cable for a couple
of feet, and I am most likely getting interference. I
plan to re-route my antenna cable. I'll report back
if this is a fix.
R/
Brandon
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