Switches hate the environment they are in... outdoor
enviornment with corrosion, etc.

I've had some luck putting radio shaft contact cleaner/lubricant
in them. On one miniature rotary--that was intermittent--I drilled a
very tiny hole with
a dremel tool (and suction to keep chips out) to let cleaner in.

It would have been a heck of a job to replace this switch.

You might see if you can work some cleaner into it.

Bill Hale

Mark Hansen wrote:
On 09/17/06 21:15, KP wrote:
On Cessna factory installed push to transmitt (PTT) is a three point
normaly open switch in the yoke. When you push the switch all three
points are shorted together. One of the points has a ground wire, one
of the other points is a MIC KEY line going to the audio panel to key
thr transmitter, the last point is a wire providing a ground for the
pilots mic audio. This way the pilot mic audio is not hot when the
switsh is not pushed. This is Cessnas cheep way of providing mic
isolation. On other audio panels the mic audio isolation is provided by
the audio panel. That is a OEM switch big bucks from Cessan!


Thanks. We're being told that what I described is just how the switch
works, not that it's broken and too expensive to replace.

Do you think the switch as I described it is defective - not counting
the design flaw?

It sure seems like a safety issue.


Mark Hansen wrote:
We have a plane in our club (1978-ish C172N) that has a problem
with the pilot's push to talk switch. It is mounted on the yoke
handle (as if from the factory, not like an after market).

When you press it gently, it works fine. If you press it too hard,
the radio continues to send the carrier, but voice is no longer sent.

Not recognizing what the problem was, after the first complaint from
ATC, I pressed harder on the switch - making the problem occur 100%
of the time. To work around this, I used the built-in hand mike for
the rest of the flight.

It was only after I got back on the ground and began diagnosing the
problem did I remember a notice from the club admin to all members
that this is just how these switches work, and that you must not
press on the switch too hard. Of course, that's just not Human
Nature ;-) If the switch doesn't work when you press it, you press
it harder.

Is this really how "these switches" work, or is the switch defective?

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA




--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA