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ronschreck
Joined: 04 Aug 2006
Posts: 192
Location: Gold Hill Airpark, NC (NC25)
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 Posted: Wed Aug 22, 2007 5:14 am Post subject: Essential buss failure |
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I wrote last week concerning this failure of my essential buss and Bob suggested I check the connections and replace the diode. I have a diode on order, but I did find that the faston connections were loose, so I crimped them down a bit. Well, the bus failed again this morning. I have found that pressing the push-to-talk switch on the SL-30 seems to trigger the failure and most of the time it is the first actuation of the switch after startup. It trips off the essential buss power for a fraction of a second, then everything returns to normal. Any ideas?
Ron Schreck
RV-8, "Miss Izzy"
Gold Hill Airpark, NC
[quote][b]
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nuckollsr(at)cox.net
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| Posted: Wed Aug 22, 2007 7:20 am Post subject: Essential buss failure |
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At 09:13 AM 8/22/2007 -0300, you wrote:
| Quote: | I wrote last week concerning this failure of my essential buss and Bob
suggested I check the connections and replace the diode. I have a diode
on order, but I did find that the faston connections were loose, so I
crimped them down a bit. Well, the bus failed again this morning. I have
found that pressing the push-to-talk switch on the SL-30 seems to trigger
the failure and most of the time it is the first actuation of the switch
after startup. It trips off the essential buss power for a fraction of a
second, then everything returns to normal. Any ideas?
|
It's a simple circuit. One diode, a couple of hunks of wire, a
few terminals. Something's loose.
Bob . . .
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hooverra(at)verizon.net
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| Posted: Wed Aug 22, 2007 2:48 pm Post subject: Essential buss failure |
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Ron,
If you are having difficulty isolating the poor connection visually.
Measure the voltages at the source and any accessible points along the
way to the E-Buss. If you used the Bridge Rectifier with Fastons this
may be 4 points. Take these measurements while the buss is loaded (your
SL30 PTT experience suggests series resistance) you will see a drop of
about 1.2 volts (unless you used a Schottky diode* *then it will be
less)* *across the diode, more than that between any two points will
isolate the poor connection.
You may also try pulling hard on each of the fastons. If you can
pull them off with moderate force they are not crimped properly.
Diodes are typically not intermittent, they generally open or short and
usually only when abused (over temp or mechanical stress)
Bad crimps are common, good crimp tools, properly sized (wire and
terminal) and high quality connectors (AMP PIDG or Molex Avikrimp) with
metal insulation support sleeves and careful installation will resolve
this.
Other things to look for are partially cut wires (rare if properly
installed), corrosion on terminals, fuse blocks, fuses.
It may be helpful to load the E-Buss with a high current device (landing
lights, pitot heat, both?) in my installation this only requires moving
a connection a few inches on a split fuse block. That will obviate the
need to key the transmitter to get the current up and thus the IR drop.
(The voltage drop is equal to the Current I * R Resistance plus any
diode junction drops that are in series)
Good luck.
--
Ralph C. Hoover
RV7A
hooverra at verizon dot net
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