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No Left Channel Audio

Flying Canuck

Flying Canuck

Well Known Member
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Not a big deal but I seem to have no sound on the left channel, for either headset jack, multiple headsets, for either radio. I have a PMA8000B audio panel with GTR200 and MGL V16 radios. No problem with right channel. I haven't checked the music input yet, but I suspect it will be the same. Since this is multiple inputs and multiple outputs, is there anything that suggests that this isn't a audio panel issue? I'll check out the fail-safe mode on my next flight today or tomorrow (power off the audio panel and COM1 should be tied to pilot headset).

Just wondering if anyone has experience with this.
 
Is the intercom audio the same? If so and the headsets weren't switched to mono, I would guess an internal issue with the AP.
 
I haven't had anyone else with me, so no idea about the intercom. I think side tone is right channel only too. It's not a headset issue, my homemade set is stereo only, the new headset that I just bought is switchable. The mono signal is from left channel, so if I set it to mono I get nothing. I get left audio only if I only partially plug in the phones.

I don't see a balance setting on the AP, so that didn't change. I too think it's the AP itself.
 
Flying Canuck said:
I haven't had anyone else with me, so no idea about the intercom. I think side tone is right channel only too. It's not a headset issue, my homemade set is stereo only, the new headset that I just bought is switchable. The mono signal is from left channel, so if I set it to mono I get nothing. I get left audio only if I only partially plug in the phones.

I don't see a balance setting on the AP, so that didn't change. I too think it's the AP itself.
Click to expand...

side tone should flow the same as intercom audio. It would seem either a chip has gone bad or a solder joint between a chip and the board has likely failed. There should be some kind of amp that takes in various line inputs and outputs discrete left and right audio after mixing. Radios are typically mono and digital processing converts it to dual channel. Though I suppose they could be physically bridging the amps inputs. Intercom and side tone are the same; only single mic input. It would be interesting if the music is still stereo. That would just point to a different chip having an issue.
 
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Before calling PS-Engineering, do this: Put a plug into the jack, then look behind the panel, see if any part of the jack is touching the metal sidewall or any other ground. I once had this happen in a 182. We tend to install jacks with clearance from other metal but forget that they get wider with a plug inserted.
You can test the intercom by plugging in both headsets. Move the mike on the headset you’re wearing away from your lips, pick up the other headset and speak directly into its mike. Swap headsets and repeat.
I agree with the others, this doesn’t sound good. But the general rule is ‘test easy stuff first, even if unlikely’.
 
I've tested the jacks on both sides - issue applies to both. I have a lot of clearance behind the panel where the jacks are installed. I will try the 2 headsets for intercom. Definitely want to exhaust all of the simple tests.

Not sure PS-Engineering will be much help, it is an older unit. We'll see what the tests come up with. If it's the AP, then I may just look for another one.
 
It’s a pretty common audio panel, plus I think it’s pin and rack compatible with some Garmin panels. Any chance you can borrow one, somewhere, and swap it in? Or swap yours into a known good installation? Then you’d know where the problem was.
 
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Yes, it's plug and play replaceable with the GMA340/GMA345 panels. I share a hangar with an avionics shop, they might have one. I'll ask today.
 
Nobody around for the avionics shop. This audio panel has issues. Fail-safe mode (powered off) gives me COM1 on the pilot headset, both ears. I have intercom in the left, but it's weaker than the right. I don't have sidetone at all. The music port doesn't work at all - can't say for sure that it did.

I'll try the drop in replacement if I can get my hands on one. In the meanwhile, I'll keep an eye out for a used audio panel. I can't justify $2700 for a new panel right now.
 
No joy on a drop in replacement at the local avionic shop, they had a PMA6000. My serial number confirms that it is discontinued so repairs are on a quote basis and estimates are $200US. That's all for bad news though. I reinserted the AP and made sure it was in securely and the left channel is working again. Probably hadn't tightened it all the way and there were contacts not being made properly.

All good now, thanks to all for allowing me to vent while I accidently fix my own issues.
 
Yes, another one of the 'try easy stuff first' things. I still recall fixing the autopilot on a 182 by unplugging, then plugging back together, a connector in the wing!
 
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