UPDATE #3 -- Headset Noise

It's not the regulator.

I'm sure that most of the time, what mikem and Jonathan are saying is true.
But my symptoms and yours sound exactly alike. I checked connections and
grounds then had the alternator rebuilt. The rebuild cost about $275. $450
total with labor. No more whine. If this were a $10,000 rebuild, I would
have spent more time diagnosing. As it was, I'm glad to spend the money and
be able to fly with confidence.

--
-------------------------------
Travis
Lake N3094P
PWK

"Jonathan Goodish" wrote in message
...
In article . com,
"mikem" wrote:

I have no explanation for the 32V reading.


I had an opportunity to poke around some more this evening.

Despite Greenlee's insistence that my meter blocks DC when measuring AC
volts (and vice versa), that appears to not be the case. The meter
reads 26 volts AC when measured on the straight battery--no alternator.
It appears to read AC correctly, and DC correctly, but not AC ripple on
a DC bus.

I have a 20 year old Beckman meter that was out of calibration, but I
calibrated for AC and DC volts against the new Greenlee. The Beckman
appears to block DC when reading AC volts.

Both meters show around 12.8v at the battery, and almost exactly 14.0
volts DC when the alternator is charging, both at the battery and the
bus. I've determined that the Greenlee's AC reading on the DC bus is
highly inaccurate, but the Beckman shows almost zero AC volts (0.008) on
the DC bus--I assume because the battery is absorbing the ripple.
However, at the alternator, the Beckman shows approximately 0.30 volts
AC, which increases to a maximum of 0.65 volts AC under full load and
max static RPM. These look more like reasonable numbers.

Could the voltage regulator be at fault? Load seems to amplify the
noise, but the bus voltage is almost exactly 14.0 volts, regardless of
load or RPM. I would think if the regulator was failing, I'd see some
fluctuation, especially under full load. Could I be missing something?

I know that it may very well still be a ground loop. There are some
oddities that I still can't explain, however, like the intermittent
static/crackling when the copilot keys the PTT and transmits. The
landing light causes occasional crackle in the audio, but a corroded
connector may be contributing to that problem, not sure.



JKG