New equipment but cant get it right.

Lowe Approach

Lowe Approach

Pre-Flight
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Jun 23, 2019
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Southern California
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Lowe Approach
SOLVED!

Hi All

New Guy here with audio issues. Brand new equipment and the installer has basically washed his hands of this project. He apparently can’t figure it out. Link to videos below.

Equipment:

Radio 1 : TKM MX170C Nav/Com replaced King KX170B same rack tray and harness (I think).

Radio 2 : TKM MX170C Nav/Com replaced King KX170B same rack tray and harness (I think).

Audio Panel : PS Engineering PMA 8000BT replaced old Cessna toggle switch style panel. I believe wiring to be new.

Transponder : Garmin GTX 335 replaced King KT76A (added ADSB out antenna Garmin GDL 82)).

VOR heads untouched

3 light marker beacon untouched



Problem.

Intermittent radio static that interferes with receiving. Both radios. Not sure about broadcast. But sometimes everything works great. I shake the wiring to the various headset ports to see if there is a loose ground or bad connection, but nothing. Turned on all other electronic equipment to see if any fluctuations, and nada. Turned on just radio one and no audio panel or radio two and get static through headphones. Turn on just radio two and no radio one and no audio panel and get nothing. Turn on audio panel and static overhead on cabin speakers and in headphones.

I tried turning off the transponder too. Still static. It does remind me of a squelch, but both radios? And they are brand new.


When turning off number 1 I noticed a glitch in the audio panel. Its shown in the last video.

I'm open to educated guesses. Hell, at this point I'm open to even uneducated guesses.

Thanks in advance.

Josh
 
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I had "interference" that was basically breaking squelch in a KX-155. It was the volume/squelch knob needed replacing in my old Tiger. Before figuring that out, they changed comm antenna coax and "unshielded" wires .. also disable the ELT to exclude interference. It would be at it worst after flying more than 20 minutes and I even thought ground frequency was doing it as it rarely happened when over 9500 feet ... not sure why, but after that fix, never had it again. That's my "uneducated" story;)
 
Turn the fluorescent lights off on the hangar? Checking radio operation in the hangars is almost useless in reality.

I ran into the lights issue then years later a usb Cigarette lighter adapter started trashing my radios, pulled that POS out and all was fine
 
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Turn the top nav/com on and leave it, and cycle the power switch on the bottom.

Turn off all nav radio channel on the audio panel, those typically constantly sprew static unless there is a vor in range and the radio is tuned to it. I bet this is your static problem, IOW I don’t believe you understand how its used.
 
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I have nothing meaningful to contribute but can't help but to add...

  • Paid $$$$ for a certified person to perform radio upgrade.
  • Radios have issues and certified person says 'I've done all I'm going to do, live with the result or find another radio guy to fix it right'.
This is part of why I'd prefer to build a kit rather than buy a 50 year old certified airplane.
 
To me the power flickering on the audio panel is low buss voltage issues, if you aren’t running this from a ground power source and have everything turned on it’s quite possible bus voltage is swinging so low that audio panel drops out when you add load to the bus. If true there isn’t anything wrong with the installation in that regard.
 
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bnt83 said:
To me the power flickering on the audio panel is low buss voltage issues, if you aren’t running this from a ground power source and have everything turned on it’s quite possible bus voltage is swinging so low that audio panel drops out when you add load to the bus. If true there isn’t anything wrong with the installation in that regard.
Click to expand...
Interesting.
How would one diagnose that and what could be the cause of the intermittency?
I guess firing it up would bring the voltage up but it was fully charged then off of the charger. I’ll try it tomorrow.

thanks
 
bnt83 said:
Turn the fluorescent lights off on the hangar? Checking radio operation in the hangars is almost useless in reality.

I ran into the lights issue then years later a usb Cigarette lighter adapter started trashing my radios, pulled that POS out and all was fine
Click to expand...
I’ll try that.
 
In my experience, chargers make terrible power supplies for ground power testing, it wouldn’t surprise me if it was about as electrically quiet as a vacuum cleaner


Astron, it’s one of my favorite tools in the hangar
 

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Sounds like you have a battery charger connected to your airplane. Chargers have poor filtering...try on ac battery alone.

If no charger, then interference from something in your hangar. How do your radios sound in flight ?
 
Lowe Approach said:
the installer has basically washed his hands of this project.
Click to expand...
Curious. So you had a shop install the equipment, perform the required function checks, sign it off, the aircraft returned to service, and then the static problems were noticed?
 
Lowe Approach said:
Interesting.
How would one diagnose that?

thanks
Click to expand...

If the audio panel is dropping out due to sudden added load of the MX170 then logically it could behave the same if you added another load like a landing/taxi light or nav lights. Or turn off a bunch of stuff and try the same test again.

Hook up an appropriate ground power source that push at least a continuous 15+ amps at 14.5 volts and try your test again.
 
bnt83 said:
Turn the fluorescent lights off on the hangar? Checking radio operation in the hangars is almost useless in reality.

I ran into the lights issue then years later a usb Cigarette lighter adapter started trashing my radios, pulled that POS out and all was fine
Click to expand...
Winner winner. It was the lights in the hangar and I feel like a fool for not considering it.
Thanks so much for the help.
 
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