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bitten192

INTERCOM

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I had low voltage inside of the cabin and sometimes the radio would not transmit at low rpm so I cleaned up my grounding terminal inside and  forward of the firewall of my REMOS G3. Now the voltage is back to normal. 1f642.png:-) and I can transmit at all rpms. However I must have bumped a wire someplace under the panel and now the intercom doesn't work 1f641.png:-( . Also the co-pilot head set does not work but both PTTs on the sticks are are OK. Does anyone have a suggestion where to start my trouble shooting (witch hunt)? There are no obvious unconnected grounds or other wires. Its a PM501 intercom.

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Some intercoms have an isolation feature. Is it possible that isolation got selected on the intercom without you realizing it? 

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When I press the onoff button on the intercom (its a push button feature of the squelch knob) I hear a click and hiss on both headsets but nothing else. The copilot headset does hear or talk to the pilot and does not transmit but the copilot ptt button on the stick causes the SL40 to transmit. The pilot side headset works fine.

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I shorted out my landing light and it tripped its breaker. The fault also destroyed my intercom without tripping its breaker. My ruined intercom acted like yours. 

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Trouble shooting - I have been having a intercom noise (squeal) that comes and goes  .  I can go 10-30mins inflight without a problem then it comes on and only when intercom is activated will it go away - comes back few seconds later when intercom is not active.    Like when you talk, the intercom is activated and the squeal goes away and few seconds later when intercom is not active anymore - the squeal is back.    I switch the intercom off then back on and sometimes it will go away and sometimes it wont.   I have tried cleaning all the contacts i can think of.   Any other ideas or anyone have a similar problem?      PM3000Model   PS Engineering

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Sure that's not noise coming from the radio?

And as always, grounds Grounds GROUNDS! Make sure they are pristine!

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Yes it is not from the radio.    After some cleaning and cleaning and cleaning - it has not come back for the last 2 flights --- fingers crossed !    thanks 

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I have installed a lot of intercoms pm1000, 3000, david clark etc. and troubleshooted a lot of them. I usually remove them completely with all jacks and start over. I always find that a lot of installers do not follow manufacturers schematic properly such as shielded wires where required and grounding only one end of shields. Lots of amateur workmanship. I never have these problems . Just get an experienced avionics person. Everything goes thru these units, mikes, headsets, speaker, com audio, nav audio an on and on. Its not rocket science but it takes someone who knows what they are doing.

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Back to static/squeal on the intercom.   Cleaned all grounds that i can see / think of.    No joy.     I noticed that the intercom (PS3000)   has a ground screw mount on the side of the unit that is not used (not connected to any wire for a ground)    I checked the wiring diagram and concluded that it is not used a there is already a ground on the pin plug correct?   However, when i have the intercom unit not touching the panel i dont get any power to the unit (ungrounded)  But i dont think the unit relies on the panel for the ground correct?   But thats what i have - no power, unless the the body of the intercom touches something that grounds it.    

Secondly, when i dont have power on the intercom i lose complete radio function even though i read that the intercom failure is still supposed to allow radio communication (but with only 1 side speaker  working).     Argh - am still searching for remedies but had to post here incase i am missing something to look for or recommendation what to do.  

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If it's not wired correctly, the pass through will not work. It calls for a very specific pinout in the installation manual.

Pin 1 is ground. Verify that you have continuity from pin 1 to the battery negative, and make sure the pin is seated and not loose in the connector. If you have continuity (good, clean continuity) and it doesn't work, you need to send the unit in for repair.

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