Buzz in headsets when transmitting - engine running

[MooneyMert]

I have a loud buzz in headsets on both radios when transmitting while engine is running and on ground.  When airborne, no buzz but tower reports transmissions are weak and unreadable.  All is quiet (no buzz) and both units seem to work when on ground and engine not running. Ground reports transmissions back as okay.  

The King 155 was just sent out to Mid Continent and returned  "repaired" with new digital readout (expensive). Re installed and original problem remains.  The other radio is a Narco 12D and works fine other than loud buzz in headset. Have Narco glideslope with DME readout. Also have Tierra audio panel and PS1000 intercom. Have a generator -no generator whine detected when running.  

The local repair facility wants to replace the Tierra audio panel and intercom hoping that problem will correct itself. Does not seem to want to troubleshoot the root problem. 

Any thoughts or guidance on this would be greatly appreciated. 

Many thanks for your input. 

Mert - KDVT

 

[Marauder]

43 minutes ago, MooneyMert said:

I have a loud buzz in headsets on both radios when transmitting while engine is running and on ground.  When airborne, no buzz but tower reports transmissions are weak and unreadable.  All is quiet (no buzz) and both units seem to work when on ground and engine not running. Ground reports transmissions back as okay.  

The King 155 was just sent out to Mid Continent and returned  "repaired" with new digital readout (expensive). Re installed and original problem remains.  The other radio is a Narco 12D and works fine other than loud buzz in headset. Have Narco glideslope with DME readout. Also have Tierra audio panel and PS1000 intercom. Have a generator -no generator whine detected when running.  

The local repair facility wants to replace the Tierra audio panel and intercom hoping that problem will correct itself. Does not seem to want to troubleshoot the root problem. 

Any thoughts or guidance on this would be greatly appreciated. 

Many thanks for your input. 

Mert - KDVT

 

Mert - I would try the co-pilot side's jacks first even if it means you put a portable PTT button in place. Many interference problems are related to the jacks and grounding.

[Baker Avionics]

Check P Lead shield grounding first.  If the shields are not grounded, ground them. Once that is completed, check in the engine compartment for cut, no longer needed, wiring.  Remove them completely.  If still there, check your coax cable and possibly even bonding of antenna.  If your antenna cable is RG58 (Black), change it to RG142 (Tan). These steps should solve your issue.  

[MooneyMert]

Thank you to all for your responses. I will pass this info along to my avionics shop for guidance! Mert

[Baker Avionics]

On 9/18/2019 at 10:10 AM, MooneyMert said:

Thank you to all for your responses. I will pass this info along to my avionics shop for guidance! Mert

Well........WHAT HAPPENED?????????

[MooneyMert]

Well the story continues.... the avionics shop advised me they found a new problem with the Terra panel.  They found a used one in Texas. It was replaced and the plane was returned to service. I flew the plane back to my home airport. On the next flight, the buzzing sound returned, only when airborne .. I then returned back to the avionic shop,  Now they indicate they found another problem with the 20 year PS intercom system.  The found a used replacement that tested out. They installed and the problem seems fixed. Just flew a long flight to New Mexico and the radios worked fine, no buzzing. In the end, I had 3 visits over 2 months to the avionics shop located at another airport, repaired my king radio, replaced my Terra audio panel and replaced my PS intercom system. Quite a lot of labor time and money ($5K) was spent tracking the problem down and finally fixing it. Moral of the story, find a different avionics shop who will take a holistic approach versus a replace each component one at a time approach. I would have spent the money differently if I knew the PS intercom was the issue in the beginning. 

 

 

[Gagarin]

You have an open diode on the alternator or a bad voltage regulator. 

[MooneyMert]

Thank you, I will check out the regulator. I do not have an alternator. 

[spectre6573]

This may help or not but I went down the path for a buzz or static and it was expensive and painful but short answer was SPARK PLUGS! I had the champions and went to tempest and it was clear as bell. 
 

now long story,

 

I narrowed it down the right mag and swap plugs and it was still there. Replaced the capacitor and it was still there. Remove antennas and check the grounding plain and reinstalled them. Then changed to new antennas and at the same time new RG cable. Then in the middle of all that, I reran the p leads.  I also installed a filter because as mention above found that #2 was staticky or buzzy and I had really had radio even close in on some of the towers. Check the wires and nothing looked bad. We after 50 hours from my last annual I check the plugs and they showed signs of wearing out and since I can’t just change a couple and have mismatch, I changed all 8 to tempest massive’s and the problem was gone. 
 

like I said, might not help and I had a bigger budget to work with but stupid plugs was my issue and I could have check the resistance at the start but I didn’t because the problem came up after 100ish on the new plugs and wires. 

[Gagarin]

On 11/13/2019 at 6:54 AM, MooneyMert said:

Thank you, I will check out the regulator. I do not have an alternator. 

Switch to an alternator. Generators brushes are very noisy when worn out.

[Baker Avionics]

By chance, check the P lead shields on the mags. And inspect engine compartment for unsed wires that are cut or capped and stowed and completely remove them. This is actually a common issue especially with Mooney's for some reason.

[Michel02]

i have a turn   coordinator  to do the same noise  when transmit   ,,,