Today's Message Index:
----------------------
1. 07:17 AM - Noisy Com (Jack)
2. 07:51 AM - Terra 200 Nav (Wayne Sweet)
3. 07:59 AM - Re: Terra 200 Nav (EuropaXSA276@aol.com)
4. 09:07 AM - Radio Noise Redux ()
5. 10:11 AM - Re: Terra 200 Nav (Earl_Schroeder)
6. 06:19 PM - OV damage to avionics: Dynon, Icom, Collins ()
Message 1
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--> AeroElectric-List message posted by: Jack <jgh2@charter.net>
The following is offered in the hope it will prevent others from
wasting time seeking the cause of a non-existent problem.
The "Problem".
The instrument panel was finished and it was time to be sure everything
operated properly before installing the RV-6A forward top skin.
Installed a temporary battery and used a hand held transceiver to
verify the Garmin 250XL would send and receive clearly using the IP
mounted mic and headphone jacks and PTT. Installed the PS Engineering
1000 intercom, pilot and co-pilot jacks and PTT switches, and verified
the intercom functioned properly with the com radio off. Turned the
com radio on and found the audio was very noisy whenever the intercom
broke squelch (although it was possible to transmit and receive clearly
from any of the three sets of jacks and PTT switches).
The Investigation.
Disassembled and checked: all jack solder joints, shields, isolation
washer sets, wire continuity and pin connections. Everything OK. PS
Engineering suggested charging the temporary battery. "Problem" solved.
Name withheld to protect the ignorant.
Message 2
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--> AeroElectric-List message posted by: "Wayne Sweet" <w_sweet@comcast.net>
I have an old (15 years) Terra ECDI that some LED's are non-op. Does anyone know
if these are repairable and who does such repairs?
Wayne
Message 3
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| Subject: | Re: Terra 200 Nav |
--> AeroElectric-List message posted by: EuropaXSA276@aol.com
Easter Avionics has some Terra / Trimbal parts. I believe the purchased the
inventory when Terra exited the general aviation biz.
Brian Skelly
Texas
Europa # A276 TriGear
See My build photos at:
http://www.europaowners.org/BrianS
Message 4
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| Subject: | Radio Noise Redux |
--> AeroElectric-List message posted by: <bakerocb@cox.net>
5/8/2005
Hello William Yamokoski, My sympathies to you with your on going radio
problems which started out with a machine gun noise when transmitting (see
both previous edited postings below).
Maybe my experience will help. I eventually solved my problem by buying some
split ferrite beads and installing them in several different arbitrarily
selected places in my comm system -- not very scientific. The noise went
away. I took a "what ever works" attiude and haven't delved any further into
the cause. Good luck.
OC
6/16/2004
Hello Brian Lloyd, and Other Willing Experts, I have a vexing problem with
the
VHF comm portion of my Garmin 430 installed in my KIS TR-1 that I'd like
some
help with. Here is the fundamental problem scenario:
1) Start engine, talk to ground control (121.8) using Lightspeed headset,
pilot's
push to talk button, and pilot's headset jacks. Everything works normally
so taxi out and make engine run up.
2) Engine run up complete, switch to tower (133.1), try to talk using same
arrangement
as in 1). The result is a machine gun like sound when I key the transmitter
-- impossible to transmit coherently. (Rapid intermittent making and
breaking
of ground contact for PTT?). Receiver works OK.....skip...
'OC' Baker, Builder of KIS TR-1 #116 4/14/97 - 11/17/03
previously from "William Yamokoski" <yamokosk@lakemichigancollege.edu>
Subject: Radio Noise Redux
Ok folks, here's the story...Been dealing with noise on transmission from
my MicroAir 760. I have
the following observations: Only occurs on transmission. Occurs no matter
what headset or jacks (pilot/copilot) combination I use. At low rpm, sounds
like a machine gun. Add a little rpm , the machine gun gets faster and
maybe a little higher pitched. Keep adding rpm and the gun gets too fast
to make out individual noises...gets to be a big blur.....skip........Bill
Yamokoski, N4970Y
Message 5
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| Subject: | Re: Terra 200 Nav |
--> AeroElectric-List message posted by: Earl_Schroeder <Earl_Schroeder@juno.com>
Last I heard, Gulf Coast at Lakeland does repair. I have a couple of
Terras purchased from them and when asked last year at Oshkosh, they
still offered repairs. Earl
Wayne Sweet wrote:
>--> AeroElectric-List message posted by: "Wayne Sweet" <w_sweet@comcast.net>
>
>I have an old (15 years) Terra ECDI that some LED's are non-op. Does anyone know
if these are repairable and who does such repairs?
>Wayne
>
>
>
Message 6
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| Subject: | OV damage to avionics: Dynon, Icom, Collins |
--> AeroElectric-List message posted by: <gmcjetpilot@yahoo.com>
What would happen to your avionics if an over voltage occurred? I did not know,
so I called and asked. The over voltage would presumably be caused by a runaway
alternator or regulator malfunction. The avionics I was most interested in
was the:
-Dynon D-10 EFIS
-Icom A200 panel mounted COM
-Collins (S-Tec) TDR-950 transponder
The question: can it handle an over voltage and what damage could take place?
**Dynon EFIS D-10: all-in one EFIS unit that incorporates a color "glass" display
of all flight instruments. Dynon meets the electronics industry standard, such
as DO-160 and can handle input voltage of 10-30V and spikes of 60V for very
short period (20ms?). The main electronics are always protected, but if the
OV is extreme or duration too long, damage could occur to the unit. However the
damage would be limited and repair cost nominal.
**Icom A200: digital flip-flop digital Com. They have a statement in the user manual
that it must be off during start for protection of circuits. It also states
power source over 16V will ruin the transceiver. I got thru to customer support.
They were helpful but admitted they had limited technical information,
and he was not one of the bench guy. However he was steadfast that the radio must
be off during start and the max volts was 15.8 volts. He did not see anything
in the circuit schematics that protected the main board from the power source
(aircraft power). Therefore he speculates that any over voltage or spike would
damage the radio? Obviously disappointed, I may check a little deeper.
**Collins TDR-950: Collins transponder sold to Meggitt/S-Tec back in the late 90's.
This design goes back a decade or two, and TDR-950s made by S-Tec are the
same as units made by Collins. The TDR-950 does not have real over voltage protection
and could get fully toasted in a worst-case OV scenario. However it does
have some sacrificial components that often fail first, such as a capacitor,
transistor and series relay, saving the main boards. However if it gets past
these first few items, it can extensively damage the transponder. The Gent I
talk to is a real technical "bench guy and seen 14V units connected to 28-32volt
power. He suggest since it draws only 1.2 amps during TX a small 2 amp fuse
would protect it, since the unit will draw more amps with higher voltage, as
he stated it. Since I only have $300 into my TDR-950 I wont worry about it too
much, but may be a 1.5-2 amp fuse might be OK. Therefore if you have a TDR-950
turn it off for engine start and shutdown. S-Te
c
stopped producing them several years ago but still supports them (because Piper
makes them). Good value on the used market.
That is all I found? Of the 3 units above, two newer units and one older design,
only one has OV protection, a new non-TSO'ed unit, the Dynon. The Icom A200,
non-TSO'ed version, does not have OV protection. The TSO'ed version of the A200
is the same, no OV protection, except it meets MIL-STD 810, which is an environmental
spec, not an electrical OV protection spec (like DO-160). Any other
radios/avionics you might have info on? Or have an opinion on OV and avionics?
I would be interested.
ALTERNATORS, INTERNAL VOLTAGE REGULATORS and OV
In the never ending quest for truth and justice
I asked two large auto electrical overhaul shops about the ND alternators and OV
failures. None seen but the common failure is an OPEN field, ie quite death
but no OV.
As far as how the OV protection works in the internal voltage regulated alternators,
I am checking. The question is can the IC predict an overload or critical
transistor problem before it is a problem. I-VR report they provide detection,
protection & limiting functions for over voltage, over current, field shorts
and over temperature. The question is how?
So how can the smart IC protect an alternator from an OV? The whole case against
the I-VR is a specific transistor short. The common reason for transistor failures
is getting too hot or a thermal runaway. Transistors have very predictable
temp characteristics and can even be used as temp probe. They have a predictable
logarithmic current vs. temp relationship. It would be easy for the IC
to monitor this characteristic and shut the transistor down well before a threshold
of melt-down. That is my story and I am sticking to it. The point to all
of this is I-VR are far better than the external voltage regulators of yesterday
or even today that have ZERO internal monitoring. Is this goodness enough
to justify not installing extra OV relays? Up to you.
Common transistors used in the VRs with the IC are the FET and IBJT transistors.
As stated before, FET failure rates of transistors are in the millions of hours.
The FET is superior in almost every way, but does have the draw back of one
of its failure modes can be a short. (Rare but possible.) The IBJT-integrated
bipolar junction transistor, is a cross between the FET and BJT junction transistor,
and they are also in common use in alternator applications. The IBJTs
common failure mode will not cause an OV. Looking at the ND voltage regulator
it appears they use the IBJT or BJT, not the FET as I first thought, but I am
still checking. Again the FET is really the best you can get and is extremely
reliable. The nice thing with the IBJT is it is almost like a FET but fails
in a different way. Either way chance of failure is very very very low. It also
points to the fact every transistor type is differnt and how they are used
determines how they might fail, so stories of trans
istors
failing in one application does not mean it applies to another.
Thanks George
(PS check the capability of this IC. Note the application and protections. This
chip is not associated with any specific alternator, just interesting.)
http://www.freescale.com/files/analog/doc/data_sheet/MC33099FS.pdf
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