Intercom problems

avi8tor50 · #1 08-11-2007, 11:17 AM

For all you electrical/audio wizards:

Have a PS engineering PM-3000. Harness by Stein.
Got it all hooked up today so I thought I would give it a try.
Audio is fine. Can listen to my MP3 player no problem when plugged into the aux jack BUT...
When I plug the mic jac into the PILOT side I get a loud whine. When I plug into the co-pilot side I get nothing. Cannot hear myself when speaking into the mic on either pilot or co-pilot side. Jacks were wired by Stein so should not be a problem there.
There was a brief period when I was plugged into the pilot side that I heard myself just fine.
Is this a problem with the unit? Any suggestions on how to try to figure this out?
All help will be appreciated.

Bob Martin · #2 08-11-2007, 06:27 PM

Not a Wizard here, but did you use the isolation washers to keep the jacks from grounding to the frame?
I just bought a PM3000 at Oshkosh and ordered a wire harness from PS so I'm all ears on this one.
Good Luck

avi8tor50 · #3 08-11-2007, 08:21 PM

Yes-isolation washers used.

Jaypratt · #4 08-11-2007, 09:19 PM

I have just started to fly the time off my new 8.
same problem, loud wine after some time flying. turn off the intercome, ps 3000, the wine goes away. will share more when the time lets me.

Frank Smidler · #5 08-11-2007, 09:29 PM

After several tries to get my PS3000 working correctly (similar issues) I was just about to pull out the wiring and start over when my 15 year son asked what the red light was for. It dawned on me that I did not push the knob in to turn it on (light turns green). Once I did it worked fine.

avi8tor50 · #6 08-12-2007, 07:47 AM

My light has been green all along so the fail safe mechanism is not indicating a problem. Today will take the mic jacks off one at a time and see if that makes a difference.

yakdriver · #7 08-12-2007, 07:52 AM

Just went through this same thing on a Glasstar. Mic grounds must run individually to the radio ground and the audio grounds to common. What I'm saying is that you can't bridge all of the grounds together to one common ground. Don

rv8180 · #8 08-12-2007, 09:06 AM

For the guys having problems, how are your system's grounds wired?
Do "all" intercom and radio grounds go to a central ground point?
Is the intercom ground separate from the aircraft ground?
Thanks!

avi8tor50 · #9 08-12-2007, 09:09 AM

I think I may have solved the problem. I was suspicious that if this were NOT a unit problem then it was a ground problem. I took the washer off the mic jack as it ran through the metal of the fuselage and allowed the mic jack to touch the side of the metal. BINGO! It worked fine! Thus, I concluded, that at this point in time the mic jack was NOT grounded. That is, with my wiring, which DID use the washers to keep all jacks floating and away from the body of the a/c there was NO ground contact for the mic.
PS engineering installation instructions state that all jacks must be floating. They also state that the shielding wire of the mic lines should be connected at the UNIT END only. I took the DB plug apart to see how Stein had wired it.
I discovered that all of the shield grounds had been wired to one of the PTT wires. The way I had connected the PTT there was NO ATTACHMENT TO THE a/c body. I just had my PTT wires connecting with fast connects as they exited the stick. I guess the assumption was that I would connect the PTT wires coming from the intercom unit to the a/c body somehow and then from there to the actual switch in the stick.
I re-connected everyting and lo and behold when I connected one of the PTT wires to the a/c body the mic worked perfectly.
I plan to check this out with Stein tomorrow and see if what I have concluded makes sense.
Don't know if this will help anyone else. I'll follow up with Stein's response tomorrow.

SteinAir · #10 08-12-2007, 11:11 AM

Since you didn't use your name I don't know exactly who you are, but if you give shoot me an email today I'll try to get hold of you this evening. Or, give me a call tomorrow and we'll figure this out.

I'm a bit confused here, because there is only ONE PTT wire, not "PTT WIRE(S)" for each jack. In fact, if you run that single PTT wire to ground, that is what kicks off the Txmt...so I'm not entirely sure what is going on here. Better to get hold of me before you do too much experimenting here - but we'll figure it out.

Definately doesn't sound correct, so we need to track down what/where the issue is.

Cheers,
Stein.