Re: UPDATE #3 -- Headset Noise

A quick way to tell a bad diode is the use of a clip on amp meter that
will read AC and DC amps. Only the Hall sensor ones will do this. Load
the output of the alternator to at least 50% of rated output and
measure the AC and DC amps. If the AC amps exceed 15% of the DC amps
you have a bad diode or stator winding. This works on all 3 phase DC
output alternators.
John

On Wed, 19 Apr 2006 22:13:56 -0400, Jonathan Goodish
<jgoodish@xxxxxxxxxxx> wrote:

In article <1145491679.393285.30420@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"mikem" <mgm17160@xxxxxxxx> 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

.

Relevant Pages

  • Re: Need Information about a Current Transformer
    ... >>> If I have 6 amps on the primary and I connect a volt meter across the ... which would drop 6 mV across your 1 ohm resistor. ... volts on the secondary. ...
    (sci.electronics.design)
  • Have meter that reads volts. Would like to...
    ... I know that a meter that reads volts and a meter that reads amps are ... What do I need to do to make a voltmeter read either volts or amps on ...
    (sci.electronics.basics)
  • Re: Need Information about a Current Transformer
    ... The meter was set on "AC volts" and it read .020 ... So what would the rateing be, 100 amps to what? ... > Don't you have a voltmeter with an "AC Volts" range? ... > it's a 1/4 watt resistor, ...
    (sci.electronics.design)
  • Re: Have meter that reads volts. Would like to...
    ... > I know that a meter that reads volts and a meter that reads amps are ... > often constructed around the same meter movement, ... > What do I need to do to make a voltmeter read either volts or amps on ...
    (sci.electronics.basics)
  • Re: Bigger alternator?
    ... like 3 amperes at 120 volts. ... it's only about 80 watts at highest setting: ... 60 or 70 is probably correct; and the alternator should ... put out at least 30 amps under load. ...
    (alt.autos.toyota)