Wiring Glitch

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Craig

Well-Known Member
Joined
Jan 30, 2003
Messages
543
Location
Jupiter, Florida
Hey guys -

As I mentioned in another post to Jake, I have a wiring problem in my Duce that is really nagging at me.

I installed the radio (MicroAir 760) per their wiring diagram. When I press the PTT, I get a loud squeal in the headphones, and the tach needle goes to the top of the scale.

Power for the tach comes from a main power bus, input from the mag switch - power for the radio thru the avionics bus.

I re-wired the jacks with shielded wires, as they are on the left of the panel, and the radio is on the right. Still squeals.

I disconnected the switch that operates radio or intercom - still squeals.

Any hints, tips, or whatever would be really appreciated!

Craig
 

Midniteoyl

Well-Known Member
Joined
Sep 3, 2003
Messages
2,406
Location
Indiana
You using a common ground bus for the two power busses? Might wanna seperate them.

Jim
 

Craig

Well-Known Member
Joined
Jan 30, 2003
Messages
543
Location
Jupiter, Florida
Grounded

Nope - separate grounds all around! Of course, all the grounds DO terminate at the same battery! Actually, the grounds are on different sides of the cockpit - four in all.
Last night I fooled around again, this time getting a rapid 'tic' in the earphones, and the tach didn't jump as much.
Also got my front cockpit door installed, and the flap hinges cotter-keyed, so the evening wasn't a total waste.
Don't you just love exasperating little problems?

Craig
 

Midniteoyl

Well-Known Member
Joined
Sep 3, 2003
Messages
2,406
Location
Indiana
this time getting a rapid 'tic' in the earphones

Hmm... check out your Coil and Spark plug wires. Just saw a guy with a squeal/rapid tick on his radio that turned out to be a bad Spark Plug wire (termination at the plug was bad). This would appear to be the same.

Jim
 
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