Today's Message Index:
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1. 09:27 AM - Re: aeroflash strobe repair (Robert L. Nuckolls, III)
2. 11:49 AM - Re: aeroflash strobe repair (C&K)
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| Subject: | Re: aeroflash strobe repair |
At 10:26 PM 7/21/2018, you wrote:
>
>I just had another aeroflash 151-0011 strobe power supply fail.
>Interestingly it was the second one I've seen with an open 330K
>resistor that was preventing triggering.
>On 12 volts the unit would almost immediately charge up to 400 volts
>and then shutdown until the voltage decayed.
>On about 6 volts the unit would charge continuously to about 300
>volts and you could hear the trigger fire but the signal was not
>getting to the white wire going to the flash tube.
>Across the 330K resistor measured about 450K in circuit and it was
>in fact open. It was the larger (1/2 watt) of the two 330K resistors
>that failed.
>Simple fix but of course the usual safety cautions of respecting
>high voltage and capacitors applies. Mine self discharged quickly
>but yours might not.
Good find. Thanks for sharing. I am mystified by
the failure of so high value of resistor. Was
it observably discolored or mechanically compromised?
1/2w was perhaps marginal. 300v/300k is one mil which
is 300 milliwatts. Was it a carbon comp?
Bob . . .
Message 2
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| Subject: | Re: aeroflash strobe repair |
It looked like a modern metal film resistor to me. Mounted parallel with
the circuit board with a light conformal coating. No evidence of it
getting hot, discolored, or mechanically stressed. In fact there was no
evidence of anything on the circuit board running hot. This unit was 12
years old and bolted to the main spar in the outboard wing bay. The
other failed unit was about 8 years old at the time and has continued
working OK since the repair. Both units were almost certainly from the
same production run.
Ken
On 22/07/2018 12:26 PM, Robert L. Nuckolls, III wrote:
> At 10:26 PM 7/21/2018, you wrote:
>>
>> I just had another aeroflash 151-0011 strobe power supply fail.
>> Interestingly it was the second one I've seen with an open 330K
>> resistor that was preventing triggering.
>> On 12 volts the unit would almost immediately charge up to 400 volts
>> and then shutdown until the voltage decayed.
>> On about 6 volts the unit would charge continuously to about 300
>> volts and you could hear the trigger fire but the signal was not
>> getting to the white wire going to the flash tube.
>> Across the 330K resistor measured about 450K in circuit and it was in
>> fact open. It was the larger (1/2 watt) of the two 330K resistors
>> that failed.
>> Simple fix but of course the usual safety cautions of respecting high
>> voltage and capacitors applies. Mine self discharged quickly but
>> yours might not.
>
> Good find. Thanks for sharing. I am mystified by
> the failure of so high value of resistor. Was
> it observably discolored or mechanically compromised?
> 1/2w was perhaps marginal. 300v/300k is one mil which
> is 300 milliwatts. Was it a carbon comp?
>
>
> Bob . . .
>
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