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Alternator noise

M

Mogli

Member
Stumped. I've got a hum in my headset when ever I turn on the alt field and can not seem to get rid of it, it increases with each system I turn on (lights, pitot heat, etc.). I have a 60 amp alt. (Van's light weight alt., pretty sure it's a plane power alt.) I've tried an alt filter on both ends of the pwr wire - no luck. Ground all radio/intcom grounds straight to battey - no luck. noise filter on pwr line to comm - no luck. Any other ideas

Thanks,

Bill
RV-8
 
alternator noise

I believe so, but I never thought to check there. I checked to make sure the plug was not hitting anything behind the panel were the plug plugs into. I'll check tonight.

Cheers,

Bill
 
Do you have any audio wires, like the wires from your headphone jacks to the radio, running in parallel with a group of power wires, or the alternator B-lead wire? You might be picking up radiated interference. I like to take extra care to keep all my audio wires as far from wires carrying power loads as I can.
 
Went out to the field and checked my headphone plug and it was not isolated (not required per directions). However, it is an option if you have noise in system. Isolated the headphones with a ground wire to battery and no change. One other piece of info. I get the noise as soon as the alternator field is turned on before I apply any power to intercom or radios.

Thanks

Bill
 
Ground wire to battery????

The radio/intercom provides the ground for the audio circuit. This is why you insulate the jack from the panel.

Try it again, without the wire back to the battery??

Also, just a bit or terminology here----the jack is mounted in the panel, the plug is on the end of the headset cord.

Are we talking about the same thing here, you have been replying with the term "plug"
 
Have you explored the Matronics Aeroelectric list & the book published by Bob Nuckols?

Look for stuff about 'single point grounding'.

BTW, is this a new plane or a new problem on an existing plane? If it's just cropped up, you might have bad diodes in the alternator itself.

Charlie
 
Alternator hum.

I had a hum in my system, occurred with the #2 alternator only. I have a dual system on my 10, using the #1, a Concord to start. Couldn't find the source. Ultimately had problems with my #2 battery, an Odyssey. The company made good on the guarantee, replaced the battery and the hum was gone.
 
Electric Oddities

Just to add to electric oddities. Have you tried a different headset. I've had some pick up noise and others not.

Ted
 
alternator noise

Thanks all for your inputs.

Sorry, the "jack" is not isolated and is not required per the directions, it's suppose to ground at the jack. A possible solution to noise is to isolate the jack and run a ground from the jack to the intercom ground (again per directions). I tried that and it did not work. I've also tried multiple headsets and same noise on all. I've a second battery that I'm charging tonight and will try to switch out battery tomorrow. If that does not work I suppose the alternator might be suspect.

This is a new airplane, the intercom was used on another RV-8 and worked fine wired as it is in this one. The only change was going from an aircraft 60 amp alt with seperate voltage regulator to a plane power 60 amp internal regulator.

Thanks again for all the info,

Cheers,

Bill
 
Frustrating Bill, I know.....

What Intercom is it again? All of the newer ones that I have seen require that the shield on the jack wiring be grounded ONLY at the intercom end - grounding at both ends sets up a ground loop, and therefore a hummmm. It might be that earlier intercoms just didn't have that in their installation procedures. (That's why half the posters told you to check it - probably the most common cause of hum these days.)

One other thing to check - you haven't mentioned if you have anything else hooked in to the audio wiring - the 296/396/496 are notorious for causing a hum if they are plugged in to both the audio system and the 12 volt power supply - they use the same ground internally, so the audio is not isolated from the rest of the electrical system. Fortunately, they seem to have finally fixed that on the 696!

Probably doesn't help you much.

Paul
 
a search on alt noise came up with 5 separate posts about noise. this post was the most active. most talk about stuff that a non builder like me just dont understand so i went another route. i put a 'filter' on the positive side of the alternator and my noise went by by. the filter is mounted on the belt adjusting bolt. we will see how this lasts.

img1066h.jpg
 
Not a PlanePower

Alternator in the photo, but still a Nipendenso. I have had three PlanePower units lose a phase, which resulted in the motorboat sound you describe. The filter you installed may have masked the problem of a lost phase. If you have...say 14.3V with minimal load, but significantly less (12-13V) with a load of about 25 amps or more, then I would suspect a a bad diode or the loss of a stator winding (broken wire) in the alternator.

Best regards,

Bill
RV-7 N151WP
Lees Summit, MO
 
bill, this alt was mounted last month. the old one had a IC diode going bad and made the same noise as this one. i have been dealing with the noise for years when flying at night with the lights on. daytime was bearable. very happy with the filter . about 30 bucks with one year warranty from chief parts.
 
turbo said:
bill, this alt was mounted last month. the old one had a IC diode going bad and made the same noise as this one. i have been dealing with the noise for years when flying at night with the lights on. daytime was bearable. very happy with the filter . about 30 bucks with one year warranty from chief parts.
Click to expand...

Can you give me the make/model filter you're using?
Thanks, Chad.
 
ferrite nodes on headphone cable

turbo said:
a search on alt noise came up with 5 separate posts about noise. this post was the most active. most talk about stuff that a non builder like me just dont understand so i went another route. i put a 'filter' on the positive side of the alternator and my noise went by by. the filter is mounted on the belt adjusting bolt. we will see how this lasts.

img1066h.jpg
Click to expand...

Anyone have an opine on putting 12$ ferrite modules on headphone cables?
 
If this is a new problem with an existing system the alternator rectifier assy may be losing diodes, increasing the AC "ripple" in the output. Another symptom of this is less load tolerance at lower RPM's.
 
Thank you RV7Charlie and rvsexr.

I'm an RV12 std system, think Im looking at shielding, grounding, and the mix bag with a ROTAX rectifier/regulator for a fix. I'm going to try two ferrite modules on my A20 chord, from aircraft spruce, and see if it can be tolerable. I don't have a regular lyc regulator to hang that nifty noise filter I saw posted on...not sure if the ROTAX system supports this kind of addition... Doug in Il

Anyway thank you....hopefully cutting it down with the ferrite modules will make it more tolerable...its perfect in ISO mode...maybe I need to disconnect the aux input IC jack at the panel since the wire travels between the seats through the tunnel to the IC on the panel and picks up noise from parallel/adjacent AP and AHARS wires in the tunnel and fuel pump etc....along the way..????
 
AirHound said:
.maybe I need to disconnect the aux input IC jack at the panel since the wire travels between the seats through the tunnel to the IC on the panel and picks up noise from parallel/adjacent AP and AHARS wires in the tunnel and fuel pump etc....along the way..????
Click to expand...
Disconnect the aux input wire at the panel and see if the noise goes away. If the noise continues you know that wasn't the problem. If it goes away then try the ferrite beads on the aux input wires right there at the audio panel. Or just leave it disconnected.

:cool:
 
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I've never touched a -12, so, having said that...

If the noise goes away when the intercom is switched to Pilot Isolate, then it's unlikely that the alternator/regulator is really the culprit. Shielding is unlikely to help much, if at all. I'd look at the areas that are getting isolated. In other words, the copilot mic/headset wiring, any aux inputs, etc. And if the plans don't show keeping all the audio ground runs isolated from the airframe, well, they're aircraft designers. :) Herding electrons is a completely different discipline. Find the intercom's installation manual, and the radios' install manuals, and follow them as closely as possible. They will likely show shields on everything; nothing wrong with that, but it's really prophylactic more than required. The reason is that the audio paths are such low impedance (<600 ohms) that it's really difficult for RF energy to get radiated into the wires. The big thing to watch is how the grounds are handled, because that's likely where your noise is getting injected.

I *think* that the stock alternator on a 912 is a 'dynamo' permanent magnet style which would mean that there's raw AC coming out of the alternator (not a big deal), and the 'regulator' is actually the diode block plus the regulator in the same package. If you're going to do any filtering of the alternator, it would be on the DC wire that comes out of the 'regulator' block and feeds 14V to the aircraft.
 
I would be looking at a bad VR in the alternator or a bad ground in the alternator circuit. Given the documented problems with the plane power connector, I would start there. Search the topic.

Larry
 
Alternator noise in headset due to aux connection

I've got a slight alternator noise in my headset that seems to be due to the aux connection from my GRT Sport EFIS. I have total silence until a certain part in the GRT boot process. It's not audible when flying, so it's not a big deal, but if I can fix it, why not.

I've read some posts that found aux connections like music input jacks causing audio noise due to the jack not being properly isolated. Not sure how I could "isolate" my GRT EFIS, since it obviously needs to be grounded.

Anyone have any ideas or have any experience with this?
 
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