v10 with lots of background noise, possible full-time hot mic

[funflyingguy]

hi all,
relatively new here, most recently needing enigma repair advice. (i got that from rainier and a local phone shop did the rest...)
my plane is a 2012 sonex 'A' model with an aerovee 80HP engine, which i bought as the 3rd owner this past may. the sonex has an MGL enigma, MGL v10, ELT and is wired for a PTT for the pilot and a separate PTT for the passenger.
back in mid-june, i had turned off the master and avionics switches, and was attempting to remove the problematic enigma. i needed to unscrew the instrument panel and the 4 circuit breakers to get to the back. in the process, i unknowingly bumped the master power switch back on and momentarily touched the circuit breaker bus to the back of the metal panel. a loud snap and a spark resulted (i shorted it momentarily). i cussed and immediately shut off the master and continued removing the enigma. i did nothing at the time with the v10. a few days later, i noticed lots of background static/noise in my headsets, making it almost impossible to hear incoming transmissions. i tried to adjust some of the more basic settings on the v10, but nothing helped much. later, i noticed the static/noise lessened considerably when i reduced the engine RPMs below 1600 but went back up as RPMs and engine noise increased. i read through some of the posts here and tried the recommendation by rainier to tightly squeeze my headphone MIC when the noise is occurring, which also really reduced the noise in the headsets. later, i sat in the plane with the engine off but avionics on, and tried squeezing and releasing the headphone mic. each squeeze i heard a click/crackle type noise in my headsets. i was told by others i should hear nothing in my headsets when squeezing the headphone mic.
is it likely i have damaged some electronics in the v10 with the short?
does anyone still diagnose and repair v10 units?
if not repairable, is a used v6 unit a plug and play replacement for the v10?
appreciate any guidance you have...... jim

[rainier]

Difficult to pinpoint the problem this way but most likely I'd think you blew a ground connection somewhere - start with the audio wiring to your headset sockets - check that all the grounds are still there. Measure if the audio grounds connect through the V10 to its power supply ground (this makes sure the ground connection inside the V10 is still OK).
If that all checks out - you mention it's related to engine RPM - so that brings your regulator/rectifier or alternator into the game and it's wiring...

[funflyingguy]

thanks rainier.

not sure i mentioned: but each time i tightly squeezed the headset mic the noise i hear was significantly reduced. is it possible the cockpit is so noisy the v10 noise cancellation is overwhelmed? i used a decibel meter in the cockpit, held near my headset, and found readings while still on the ground stationary, at 1000, 1500 and 2000 RPMS that were consistently in the 100 - 105 DB range. havent been able to get up flying to test the DBs yet....

an electronics friend checked the audio and v10 grounds and found them to be good. so onward i go....

[rainier]

If you can mute the noise using your hand over the mic then you know the noise is getting in via the mic.
You don't mention which of the four noise suppression systems you have selected nor the level set.

Note that the noise suppression works related to expected microphone levels so it is important to adjust the mic gain correctly in the setup. The way to do this is to select an unused channel and TX while speaking into the mic - now let go of PTT and continue speaking. If your level is setup correctly then there will be no different in volume of your sidetone in the headset.
This is because the TX uses automatic gain adjust of the mic level while the intercom does not - so the TX sidetone is the correct level and can be used as a reference. If you find the sidtone during TX too low for example - it means you need to increase volume and decrease mic level.

[funflyingguy]

excellent, thanks. i will try this ASAP.

FYI: i am presently at range 2 and level 2 for noise suppression on my v10.

[funflyingguy]

hey ranier,

as i browsed through my v10 unit menus, i noticed we may have a terminology difference.

for instance, you refer to four 'noise suppression systems'... i dont see anything labeled like that. the closest i have is under VOGAD, with a VOX, LOW, MEDIUM and HIGH ranges. within each you can set level from 1 to 8 or 1 to 10, not sure which it is. i am presently at MEDIUM range level 2.

when you refer to MIC GAIN, are you referring to MIC level under setup? i am presently at 10DB but before you responded i was at 20DB.

FYI: today i tested on an unused channel and spoke into the PTT. continuing to talk i released the PTT. the volume remained the same.
also: after my MIC level change from 20DB down to 10DB, i dont get the loud cockpit noise until i get up to nearly 2000RPMs. it was 1500 to 1600 RPMs when testing this a few days ago. sounds like progress to me.

thank you! if you have any other suggestions or comments to lessen the background noise even more, please let me know. FYI: i bought a new ANR headset a couple of weeks ago, but have not really turned on the ANR feature yet. all i have mentioned here has been in the passive headset mode.

i read somewhere here or in the v10 manual, that if you turn on your ANR headset, you should change your VOGAD range from LOW, MEDIUM or HIGH to the VOX range then adjust the level within that accordingly. have you found this to be true?

[funflyingguy]

latest tests...

in between efforts to diagnose an aerovee engine oil leak, i tried turning the MIC level down even more (worked last time!). now at 5, the MIC doesnt let in cockpit noises until about 2500 RPMs when stationary. (i usually cruise at 3000 - 3200 RPMs) however, i noticed that the TX sidetone is now slightly louder than the volume i hear when using the intercom. is there a technical reason why the sidetone should be the same as the intercom volume, or, is this just a guideline/preference?

[rainier]

During TX the radio uses automatic gain control to set the mic level (the gain needs to be exactly right so the V10 can modulate the carrier perfectly so you get max range from the available power).
So since sidetone means you are listening to your outgoing transmission you can use this as reference to adjust the mic level for the intercom which is not automatic (or else it would keep increasing the gain to some limit if nobody is talking).
The noise canceling built into the V10 is designed to operate on a set audio level range so if your level is too low or high the noise canceling is not going to work well.

[funflyingguy]

so i finally got to fly yesterday and make additional V10 transceiver adjustments. right now, the noise abatement is the best it has been for months. nearly all the MIC noise is gone at all RPMs. all that is left is occasional loud static background noise for a few incoming transmissions, usually made by a pilot some distance away. my latest settings are as follow:

VOGAD - medium 3 (i tried low from 1 - 3, but got better noise control in the medium range)
MIC level - still 3 DB
VOL - just below 1/2.
SQL - still at 1/2.
ANR headset - still not using the ANR function

not sure why the loud background static is only heard for just some of the incoming transmissions and not all. could this be weak incoming transmissions? any way i can filter these out too?

.... jim