Transmission feedback on C206 Towplane

[[email protected]]

Got a Cessna 206 that emits a steady tone during transmission only.
The pitch increases with rpm to a point where ATC refuses service. No
tone is emitted on battery power only (Alt. off). No problem
yesterday, problem today. Noise remains with audio panel on/off, using
L/R trans switch, speaker on/off, swapping headsets(Bose). Aircraft
has 95 amp alt. (belt drive), noise filter. Please email me if more
infor. is needed.
Thanks
R

[Ralph Jones[_2_]]

On Sun, 29 Jun 2008 08:57:09 -0700 (PDT), "
> wrote:

>Got a Cessna 206 that emits a steady tone during transmission only.
>The pitch increases with rpm to a point where ATC refuses service. No
>tone is emitted on battery power only (Alt. off). No problem
>yesterday, problem today. Noise remains with audio panel on/off, using
>L/R trans switch, speaker on/off, swapping headsets(Bose). Aircraft
>has 95 amp alt. (belt drive), noise filter. Please email me if more
>infor. is needed.
>Thanks
>R
Sounds like a bad noise filter on the alternator.

rj

[[email protected]]

Take the alternator off and have your local alternator shop check the
"diodes" in it. They are not certified to repair it but they can sure
check it out for you. Bad diodes will cause a hum that changes in
pitch with rpm. They can also cause the alternator output to be
unstable as seen in a quivering amp meter.

[Gary Boggs]

I had a problem like this and it turned out to be a bad ground on the
ptt.

On Jun 29, 2:34*pm, wrote:
> Take the alternator off and have your local alternator shop check the
> "diodes" in it. *They are not certified to repair it but they can sure
> check it out for you. *Bad diodes will cause a hum that changes in
> pitch with rpm. *They can also cause the alternator output to be
> unstable as seen in a quivering amp meter.