klehman(at)albedo.net
Guest
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 Posted: Mon Aug 06, 2007 12:37 pm Post subject: Strobe whoop whoop wine |
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> We have completed 130 flight hours with our Z-14 wired subaru now
> without any nuisance OV trips. The only electrical issue is that I
> recently purchased a comfortable David Clarke headset and with our
> fairly quiet engine, I now hear weak but annoying strobe whine that I
> couldn't hear in cruise with other headsets. I have already followed
> most of your wiring recommendations so it may take me awhile to solve
> this one especially since the strobes operate off a different
> alternator and battery as the radio and intercom.
Start with a test battery made up of a couple 6v
lantern batteries to run the strobe supply with a
short cable and batteries located right at the power
supply. You need to deduce the propagation mode. I suspect
it's conducted and a relatively simple filter at the
power supply will fix it.
Bob . . .
It is a pain to pull my wingtips to get at the aeroflash power supplies
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and I have not done that yet. However I have powered the strobes from a
separate battery with their normal fuse pulled and I still hear the
noise faintly in the headset even with the engine, master switch,
intercom, and radio turned OFF. It is a bit louder with the intercom
powered up but I was not expecting to hear it with the intercom and
radio turned off. It is a metal airframe and the strobe power supplies,
the comm radio, and the intercom are all grounded to the airframe
because they are all internally grounded to their respective cases. The
headset jacks are insulated from the airframe (in a plastic box) and
wired with shielded wire. Thinking it could be a ground loop situation
I tried grounding the temporary battery to a screw on the wing spar but
it did not seem to make a difference. Adding some inductance to the
+power lead and some electrolytic capacitors made no diference.
Before I pull the wingtips I'd like to have a plan and any needed parts
on hand. I will look for some automotive radio power supply filters and
pick up some nylon bolts to insulate the power supply from the airframe.
Any other suggestions? Is there any point adding some capacitance to
the headphone audio circuit to try and bypass some of the higer
frequencies. This noise was not bothering me until I replaced one
headset with a DC H10-13.4.
thanks
Ken
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