My DC H10-76 headset isn't working right. It was brand new 3 weeks ago, so it's not like it's worn out. What's happening is it's almost completely inaudible. I first noticed it on today's flight at two different stations in the airplane. It was so bad that I had to hand comm over to the copilot for the entire sortie because i couldn't reliably hear what was being said to me by ATC. This was with all aircraft volume control and headset volume turned up to the highest level. Blowing as hard as I could on the microphone produced a barely audible sound in the headset, and I can hear SOME sound over the headset, just very quiet, like the volume has been turned way down even though in reality it's at it's max setting. Had the same result when I pluged it into 2 different stations on the ground, so I'm pretty sure it's the headset and not the audio source.

I'm suspecting possibly the mic cord has been plugged in improperly, it's the only thing I can think of aside from an internal fault. There are no visible frays or other damage to the wires or headset itself, and it has never been dropped or otherwise abused. The mic cord is marked NEXUS on one side of each plug with numbers on the opposite side of the plug. If you have a DC set, could you please look and see what your plugs look like? should it be "NEXUS (male plug) -> (female plug) NEXUS" or NEXUS (male) -> (female) U-172/numbers?

Any other troubleshooting would be appreciated.

I know on the DCS we use, there is a gain/volume controll in the PTT box itself.  Seem like every year or so I have to call a tech to adjust it.

My step one in troubleshooting would be to take it to comm/nav.

Can't you just tell the life support folks that it's broken and have them get it fixed?

ya, there's a volume knob on the main clamshell, but i already have it maxed out, i can tell from the complete silence on one side of the switch and the barely audible sound when it's turned all the way in the other direction.  i wish it was something as simple as the idiot switch!

Quoted: My step one in troubleshooting would be to take it to comm/nav. Can't you just tell the life support folks that it's broken and have them get it fixed?

nope-- the shop on base only deals with the helmet/mask mounted stuff.  There's no D/C rep on base or in the area and nobody knows how to service them.  I already took it to life support and they basically threw up their hands and told me to get it replaced sight unseen.

The one I have in front of me has them nexus:numbers, but I'm reasonably sure that has nothing to do with the audio quality.

If there's nobody there that will look at it I would be inclined to just get them replaced.

I have completely rebuilt many H10-76s, I know them like the back of my hand.  I also have  a bunch of spare parts, but I am on leave and not where they are.  Go to the DC website and get the schematic for the headset, get a multimeter (I am of course assuming you can use one) and check out the earphone circuit.  IIRC it uses a 100 ohm pot and the earphones themselves are about 20 ohms each, so your resistance should vary smoothly between about 40-140 ohms when you cycle the volume knob up and down.  You could have a bad cord too, but it could be any of them.  You may have a bad solder joint at the U194 connector itself.

Schematic

You really need to go find the avionics back shop (take a 6 pack of beer, it will get fixed!), since life support is not taking care of it for you.  

This headset didn't take a slide across any driveway pavement perhaps... did it?





I keed! I keed!  


(Reminds me that I need to dig my headset out and dust it off and sell it. Haven't been in a cockpit in years.)

What type of Aircraft and radios are you trying to use the H10-76 headset with.
The I believe the H10-76 is a military type low impedance headset with 8 ohm earpieces, the civilian radio world uses 600 ohm impedance headsets.
If you are plugging a low impedance headset into a high impedance system you would get the exact problems you are describing.

Try it on another similar aircraft similar avionics and jacks, if no workee, headset, if workee avionics on original aircraft with the problem

did you throw it down the driveway to break it

Quoted: What type of Aircraft and radios are you trying to use the H10-76 headset with. The I believe the H10-76 is a military type low impedance headset with 8 ohm earpieces, the civilian radio world uses 600 ohm impedance headsets. If you are plugging a low impedance headset into a high impedance system you would get the exact problems you are describing.

Actually, no.  The microphone impedance/type is different, not the headphone impedance.  We use civilian headsets/microphones (NSN numbered H10-13.4s) on the C-17, but most other .mil aircraft use the old school H10-76s.  If you plug the wrong one in you will get a high pitched squeal when you try to transmit/talk but the headphone portion works fine.  We actually have a hi/low impedance switch at the ground refuel panel so you can use either type.  DC also has a dual impedance headset out now, the H10-60 IIRC.  

Quoted: This headset didn't take a slide across any driveway pavement perhaps... did it? I keed! I keed!   (Reminds me that I need to dig my headset out and dust it off and sell it. Haven't been in a cockpit in years.)

What kind of headset?  

Quoted: Quoted: What type of Aircraft and radios are you trying to use the H10-76 headset with. The I believe the H10-76 is a military type low impedance headset with 8 ohm earpieces, the civilian radio world uses 600 ohm impedance headsets. If you are plugging a low impedance headset into a high impedance system you would get the exact problems you are describing. Actually, no.  The microphone impedance/type is different, not the headphone impedance.  We use civilian headsets/microphones (NSN numbered H10-13.4s) on the C-17, but most other .mil aircraft use the old school H10-76s.  If you plug the wrong one in you will get a high pitched squeal when you try to transmit/talk but the headphone portion works fine.  We actually have a hi/low impedance switch at the ground refuel panel so you can use either type.  DC also has a dual impedance headset out now, the H10-60 IIRC.

According to DC the H10-76 is low impedance mic and headset.
www.davidclark.com/avHeadsetSpecs/avSpecs.aspx?ModelName=H10-76

You most certainly can use a civilian headset in a military setup (after a sort) but you cant use the military headset in the civilian world without impedance matching.
That's why I was wondering what type of A/C radio system he was plugging into.

Quoted: Quoted: Quoted: What type of Aircraft and radios are you trying to use the H10-76 headset with. The I believe the H10-76 is a military type low impedance headset with 8 ohm earpieces, the civilian radio world uses 600 ohm impedance headsets. If you are plugging a low impedance headset into a high impedance system you would get the exact problems you are describing. Actually, no.  The microphone impedance/type is different, not the headphone impedance.  We use civilian headsets/microphones (NSN numbered H10-13.4s) on the C-17, but most other .mil aircraft use the old school H10-76s.  If you plug the wrong one in you will get a high pitched squeal when you try to transmit/talk but the headphone portion works fine.  We actually have a hi/low impedance switch at the ground refuel panel so you can use either type.  DC also has a dual impedance headset out now, the H10-60 IIRC.   According to DC the H10-76 is low impedance mic and headset. www.davidclark.com/avHeadsetSpecs/avSpecs.aspx?ModelName=H10-76 You most certainly can use a civilian headset in a military setup (after a sort) but you cant use the military headset in the civilian world without impedance matching. That's why I was wondering what type of A/C radio system he was plugging into.

You are correct, the civilian headsets have 300 ohm earphones instead of 20 ohm ones.  I have known a lot of people that used their H10-76s on C-17s (high impedance/civvie type comms) with only a microphone swap though.  There is enough adjustment in the volume pot to make it work.  The mics are most definitely not interoperable though.  The avionics shop at McChord will just zip tie a high impedance mic on the boom of your H10-76 so you can switch between mil/civvie systems with just a simple swap of the plug.  

sorry if I wasn't clear, I'm a military student pilot flying the T-1A.  It's a Beech 400, but has been militarized including military radios.  This same headset has worked just fine for several flights prior.  Today I plugged into a seldom used jack (in the aft cabin) and it hasn't worked the same since.  The guy who sat in that seat after me described a similar problem, however his was not as bad as mine.  His set worked normally for him on the first half of the sortie when he was in the front seat and he didn't try the front seat again after sitting in the back cabin.

Could a bad jack short out the headset?  All wires and connections visibly look fine.  The solder on the plug also looks fine when i pull up the covering on it.  

I have no means or know how on how to test the ohms output on it.

Quoted: sorry if I wasn't clear, I'm a military student pilot flying the T-1A.  It's a Beech 400, but has been militarized including military radios.  This same headset has worked just fine for several flights prior.  Today I plugged into a seldom used jack (in the aft cabin) and it hasn't worked the same since.  The guy who sat in that seat after me described a similar problem, however his was not as bad as mine.  His set worked normally for him on the first half of the sortie when he was in the front seat and he didn't try the front seat again after sitting in the back cabin. Could a bad jack short out the headset?  All wires and connections visibly look fine.  The solder on the plug also looks fine when i pull up the covering on it.   I have no means or know how on how to test the ohms output on it.

I've never seen a bad interphone box short out a headset but I suppose it is possible.  All you can really do is make sure all the connections are secure, and try it again on a different aircraft. Can you just swap the headset out for one that works?  If not, like I said find the avionics backshop (though since you are AETC you won't have any active duty maintenance).  If there is such a thing there they will probably have  drawer full of headset parts, and they can also check it out with a meter for you.  

N_T what platform you flyin'?

Quoted: N_T what platform you flyin'?

I took the set to the one shop on base that deals with most pilot equipment including all the helmet mounted radio gear, but apparently they don't touch the headsets nor do they know who does.

I tried it on the Scot tester used to test all the comm gear before crews step to the airplane.  Two different testers produced the same results that I got in the airplane-- VERY muted volume to the point of it being inaudible.  This leads me to believe it is indeed the headset and not what it was plugged into.

I'm going to go to the sim building tomorrow and see if there's anyone there who can help.  They are not AF, they are contract and use the headsets on all the sims, so it's possible that they have someone there who can help with it.

Damn frustrating!  I'd bust it open myself and try to tinker with it, but I know nothing about it and I'd rather not owe the gubbmint $300 for dicking up an already dicked up headset that I could get repaired or replaced for free.

Quoted: did you throw it down the driveway to break itgive it that used look

Quoted: Quoted: N_T what platform you flyin'? www.strategic-air-command.com/aircraft/trainer/images/t1_jayhawk.jpg I took the set to the one shop on base that deals with most pilot equipment including all the helmet mounted radio gear, but apparently they don't touch the headsets nor do they know who does. I tried it on the Scot tester used to test all the comm gear before crews step to the airplane.  Two different testers produced the same results that I got in the airplane-- VERY muted volume to the point of it being inaudible.  This leads me to believe it is indeed the headset and not what it was plugged into. I'm going to go to the sim building tomorrow and see if there's anyone there who can help.  They are not AF, they are contract and use the headsets on all the sims, so it's possible that they have someone there who can help with it. Damn frustrating!  I'd bust it open myself and try to tinker with it, but I know nothing about it and I'd rather not owe the gubbmint $300 for dicking up an already dicked up headset that I could get repaired or replaced for free.

It probably has a high resistance short somewhere, maybe one earphone or the other.  If the potentiometer (volume adjustment) goes bad it usually just has one or more dead spots or is open and you hear nothing at all.  Does the volume adjustment seem to work when you turn it up and down, or can you even hear enough to tell?  

at max volume on the knob i can just barely hear a hiss when i blow hard into the microphone, and then just about anything out of max i hear nothing, so i know that there is SOME sound comming through it.  In the airplane I could hear the radios and interphone when everything was cranked up to max volume-- a setting that normally would be deafening, but it was still faint.  I could not hear myself AT ALL.  The sound seemed to be even (no ear louder than the other) but faint on both sides.

Well it's definitely not something you can fix yourself.  You'll need a multimeter and a soldering iron at minimum to fix it.  I'd just turn it in and get it replaced.

damnit.... looks like i'm up for a trip to the orderly room to try to beg a new set off of them... lucky for me it's still the beginning of the fiscal year so it shouldn't be much of a fight to get it back.

sad thing is they will probably just trash it instead of sending it in for warranty work.

thanks for the help.  i was hoping it was a simple fix, but apparently not.

Quoted: damnit.... looks like i'm up for a trip to the orderly room to try to beg a new set off of them... lucky for me it's still the beginning of the fiscal year so it shouldn't be much of a fight to get it back. sad thing is they will probably just trash it instead of sending it in for warranty work. thanks for the help.  i was hoping it was a simple fix, but apparently not.

If they are going to toss it ask them if you can keep it and send it to me, I'll fix it up and you can have a spare set.    





(I have at least 4 DC headsets at home.  , I bought one and the others have been issued or resurrected from piles of parts.)

Quoted: sorry if I wasn't clear, I'm a military student pilot flying the T-1A.  It's a Beech 400, but has been militarized including military radios.  This same headset has worked just fine for several flights prior.  Today I plugged into a seldom used jack (in the aft cabin) and it hasn't worked the same since.  The guy who sat in that seat after me described a similar problem, however his was not as bad as mine.  His set worked normally for him on the first half of the sortie when he was in the front seat and he didn't try the front seat again after sitting in the back cabin. Could a bad jack short out the headset?  All wires and connections visibly look fine.  The solder on the plug also looks fine when i pull up the covering on it.   I have no means or know how on how to test the ohms output on it.

Have him check his on the ground test set and see if it normal.  If his is 'weaker' than it was before, there may be an issue with the aft cabin panel toasting what is plugged into it.  I don't do aircraft but have worked on enough headsets the tv guys wear to never want to see another.