R

rulmen

Active Member
I have a PS Engineering PS-501 intercomm attached to a KING KA-134 Audio panel. I was working behind my panel (already flying aircraft) and I must have bumped a wire or something under the instrument panel.

When I key my radios (either of them) they transmit, but my mike audio doesn't transmit. I have tried to plug into the Co-Pilot jacks and I have the same symptom. The intercomm works perfectly. (I have an ICOM A200 and a TKM MX-11. they are connected as COM1 and COM2). This all worked before but I must have messed something up behind the panel.

Please see the attached technical data. Does Anyone have any ideas?

http://www.ps-engineering.com/docs/PM501_IM.pdf

http://www.aeroelectric.com/Installation_Data/Bendix-King/KA134.pdf

I cant figure out what pin takes the transmit microphone audio from the jacks to the audio panel. Does it go thru the PS-501? HELP!!
 
First thing...does the intercom still work and can you hear each other when plugged in? When you hit the PTT, does the Tx come on for the Intercom and radio? If so, then it's likely the Mic audio between the audio panel and intercom. Do you hear a Click or carrier but no voice? That also points to a mic audio line. If no Tx or carrier click, the possibly a Mic Key/PTT wire. It's likely something simple, so don't get too concerned!

Cheers,
Stein
 
Audio problem

SteinAir said:
First thing...does the intercom still work and can you hear each other when plugged in? YES
When you hit the PTT, does the Tx come on for the Intercom and radio? Yes

If so, then it's likely the Mic audio between the audio panel and intercom. Do you hear a Click or carrier but no voice? Yes

That also points to a mic audio line. Cool! Was hoping someone had the pinouts for both the intercom and audio panel.... Im thinking pin 12 on intercom to pin (UNKNOWN) on the KA-134. That is what I need to know..

If no Tx or carrier click, the possibly a Mic Key/PTT wire. It's likely something simple, so don't get too concerned!

Cheers,
Stein
Click to expand...

http://www.aeroelectric.com/Installation_Data/Bendix-King/KA134.pdf
 
SteinAir said:
First thing...does the intercom still work and can you hear each other when plugged in? When you hit the PTT, does the Tx come on for the Intercom and radio? If so, then it's likely the Mic audio between the audio panel and intercom. Do you hear a Click or carrier but no voice? That also points to a mic audio line. If no Tx or carrier click, the possibly a Mic Key/PTT wire. It's likely something simple, so don't get too concerned!

Cheers,
Stein
Click to expand...

1. Yes works great. Can hear others fine.
2. When PTT is hit the TX lights come on in the selected radio.
3. Yes I hear a click/carrier when the PTT is pushed, but no voice from either pilot or co-pilot.
4. I believe it is the mic audio line also, but I cant figure out which one it goes to in the audio panel.

Thanks!!
 
Without knowing how your system is wired, it's not possible to give you a 100% solution...I assume you don't have a diagram of your avionics interconnects? Also I wouldn't expect a lot of answers, because this setup hasn't been common for decades, so it's unlikely there are a lot of folks with that installation. I assume you verified your symptoms above with a handheld radio or someone else listening? If your notes still hold true then the volume would have no effect on the Mic Audio. However, if the transmission is going out fine and you can't hear it, then that's a different story altogether. I also assume you can still receive transmissions just fine?

That said, here's what I'd do if it were in my shop after verifying a number of the above things:

1) Start at the PM-501 (which is a known quantity with a standard set of wiring) and find the "Mic Audio High" wire - which is pin #12.

2) Either manually follow that wire, or get a multi-meter and ring it out to wherever it's connected on the KMA.

3) It's likely to be installed into pin #19 on the KMA, but not 100% certain.

That's about it. Just make sure you know what the pin numbers are depending on which side of the connector you are looking at. Your symptoms point to this as a starting point, but it's not a slam dunk either.

Let us know what you find out.

Cheers,
Stein
 
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Audio Problem

Tried the Pin 12 to Pin 15, didn't work. I give up, called in a pro. Thanks for the help, i'll advise with the final word.
 
Actually, looking at this closer it appears that it's more likely to be "Z" or "Y"....

Cheers,
Stein
 
Not sure how this was installed but if following pm-501 wiring diagram, the output of the intercom should go to a separate mic jack that is wired to the audio panel. Normally it is installed this way, so a hand mic can be used to bypass the intercom in case of failure. If that is the case, this is a place to look. There should be 2 wires to each terminal. Very easy to bump and break a wire at the solder joint. Good luck.

Jay
 
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