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s_kilishek(at)yahoo.com
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 Posted: Thu Dec 28, 2006 9:40 am Post subject: What Are The Odds (Was Over Voltage) |
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Never to be deterred by experience, I installed yet
another new VR749 regulator the other day. This was
the fourth one. It worked fine for about 20 minutes,
then showed the same behavior as the other three:
oscillations between overvoltage of 15+ volts and
apparent cut off.
What are the odds that four consecutive regulators
would be bad?
Is there anything else in a plane wired per Z22 that
could account for this behavior?
Temperatures here are in the 40s and 50s. Could a
negative temperature coefficient be causing the
regulator set point to rise above 15 volts?
George
Dennis Haversham wrote:
I have the same regulator (VR 749) controlling a 100
amp Mazda
alternator. I'm running the engine on the ground
while I finish the A/C
but I've experienced the same thing. High voltage at
the battery...
Sally Kilishek wrote:
| Quote: |
I'm using a generic Ford regulator (Wells VR749) and
a
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| Quote: | B&C OVM-14 overvoltage module wired as per Z-22 in my
RV8.
It worked fine for a short time, but after about 4
hours of flying, the overvoltage indicator light
started flickering. Bus voltage is rising above 15
volts (one time as high as 16 volts), then dropping
back below 15 volts and immediately rising again.
It looks to me like the regulator isn't regulating
and
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| Quote: | that the OV module is cutting off the field
excitation
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| Quote: | until voltage drops below 15.
I've replaced the regulator twice, but the problem
continues.
Is there somewhere else I should be looking?
George
N57GK
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cjensen(at)dts9000.com
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| Posted: Thu Dec 28, 2006 11:43 am Post subject: What Are The Odds (Was Over Voltage) |
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George,
Are you measuring the voltage with a minimum of two different
instruments? In short, are you sure it is the voltage and not the
measuring device/indication? You may have been over this territory
before but I didn't see it in the email history below. Perhaps common
to all the failures was the same measuring instrument?
Chuck Jensen
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sarg314(at)comcast.net
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| Posted: Thu Dec 28, 2006 12:35 pm Post subject: What Are The Odds (Was Over Voltage) |
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Sally:
In general the odds are pretty close to 0 unless all four came from
the same production lot AND the whole lot was bad. Having spent 20
years in the electronics business I've seen that happen a few times. Of
course we bought capacitors, circuit boards, IC's, memory, etc. in
rather large quantities. Your regulators may have a lot number printed
on them that you could compare to see if they're all the same.
That said, it's probably more likely something in your circuit is
killing the things rather than getting 4 duds in a row.
--
Tom Sargent
Sally Kilishek wrote:
| Quote: |
Never to be deterred by experience, I installed yet
another new VR749 regulator the other day. This was
the fourth one. It worked fine for about 20 minutes,
then showed the same behavior as the other three:
oscillations between overvoltage of 15+ volts and
apparent cut off.
What are the odds that four consecutive regulators
would be bad?
|
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http://www.matronics.com/Navigator?AeroElectric-List |
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