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KY96A issue

WingsOnWheels

WingsOnWheels

Well Known Member
I have a KY97A and a PMA5000EX audio panel. Intercomm works great, transmissions are great. However, receive is clear, but very quiet. Even with all the volumes up I can barely hear the radio. I have tried with the intercom off (pass through mode) and it is the same. The result are the same with different headsets in both sets of plugs. All the other audio inputs are loud and clear.

Any ideas?

Edit, KY97A, not 96
 
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Speaker Impedance

I would check the impedance of your speaker or head phones. There was an post here a while back about this. Apparently aviation headphones are different impedances than consumer electronics. Dont know much more about this.
 
Trouble-shooting by remote vision is pure guess work, but here?s my guess:
First, while listening to the weak signal, does it get even weaker, going to zero, when you turn down the volume control on the KY96? If no, then I would look hard at that control, it may be defective. However, my guess is that the answer is yes. If so, look very carefully at your wiring between the two units. What you are looking for is a single strand of wire, probably at one of the pins, which is shorting to another pin or ground, ?stealing? most of your signal. If you have a pin extractor, you might even replace this wire with a new one, see if that fixes the problem. If you used shielded cable, look for a short between the shield and center wire. These can be tough to spot. If you pull the cable you can test with an ohmmeter for a short.
 
BobTurner said:
Trouble-shooting by remote vision is pure guess work, but here?s my guess:
First, while listening to the weak signal, does it get even weaker, going to zero, when you turn down the volume control on the KY96? If no, then I would look hard at that control, it may be defective. However, my guess is that the answer is yes. If so, look very carefully at your wiring between the two units. What you are looking for is a single strand of wire, probably at one of the pins, which is shorting to another pin or ground, ?stealing? most of your signal. If you have a pin extractor, you might even replace this wire with a new one, see if that fixes the problem. If you used shielded cable, look for a short between the shield and center wire. These can be tough to spot. If you pull the cable you can test with an ohmmeter for a short.
Click to expand...

That is good advice, thank you. The volume knob is working, just very low. Since it is only the comm, that makes it easy to check. Ill check ground faults.
 
So Im at the hangar working on the comm right now. I have the comm and audio panel both out of the racks. I am showing no connection between the headphone out "H" pin on the comm and ground or the shield. I confirmed that it is connected to the correct pin on the audio panel and resistance from the comm pin to panel pin is effectively zero.

I am going to clean the edge connector on the comm, but it has been in and out recently.

Any other ideas. Bad comm?
 
Put the com back in. Jumper the pin at the audio panel connector directly to your headphone (connect ground to the plug, too.) Turn on com. If volume is normal, problem is downstream (audio panel or wiring). If you can barely hear it, as before, then the issue is internal to the com, and time for plan B - fix or replace.
 
BobTurner said:
Put the com back in. Jumper the pin at the audio panel connector directly to your headphone (connect ground to the plug, too.) Turn on com. If volume is normal, problem is downstream (audio panel or wiring). If you can barely hear it, as before, then the issue is internal to the com, and time for plan B - fix or replace.
Click to expand...


The audio panel goes to pass-through mode if it is powered off or fails. I have tried the comm with the audio panel off and get the same quiet result. I brought the comm home with my to either bench test myself, or take to the avionics guy to be tested. If it tests ok, then I need to find a way to test the audio panel, maybe try a different input.

Ill try your method next time i go to the airport.
 
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I swapped the comm into another aircraft, same problem, so bad comm. I am going to have the shop take a quick look. Possibly nor worth fixing though.
 
There is a "sidetone" adjustment potentiometer that you can access from the top of the unit. Turn it up a little with a screwdriver and see if that helps. See the King KY 96A/97A installation manual available with a Google search. There is a picture of the accessible adjustment pot locations. There might be a similar pot for radio reception level inside.

We just removed an overhead speaker in a Super Cub with a KY97A transceiver and my memory of the manual is still fairly fresh on that unit. So....

You might want to make sure there isn't a 4 ohm resistor across pins E and 5 (speaker output designated 4 ohm audio Hi and Lo, respectively). Older King radio models required a dummy load in absense of a speaker. That could affect the headphone out circuit due to internal cross linking. The KY97A doesn't typically need that dummy load resistor but I might remember some nuance based on the exact dash number on the KY97A. Again refer to manual. Some unwitting tech in the past may have integrated that obsolete requirement for a resistor. Since you swapped the unit into a different airplane that probably rules out said resistor externally but maybe something internal or the second airframe might have that resistor while yours doesn't. Did you try putting the other aircraft's radio into your aiframe?

In the end maybe a bench check would be less trouble for initial troubleshooting than all that fiddle. Used KY97A's are readily available on the open market.

If you decide to update to a new transceiver you might consider Garmin GTR 200, Trig brand TY91 / TY96A, or the Icom A220 with optional King slide-in adapter.

Jim
 
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jliltd said:
There is a "sidetone" adjustment potentiometer that you can access from the top of the unit. Turn it up a little with a screwdriver and see if that helps. See the King KY 96A/97A installation manual available with a Google search. There is a picture of the accessible adjustment pot locations. There might be a similar pot for radio reception level inside.

We just removed an overhead speaker in a Super Cub with a KY97A transceiver and my memory of the manual is still fairly fresh on that unit. So....

You might want to make sure there isn't a 4 ohm resistor across pins E and 5 (speaker output designated 4 ohm audio Hi and Lo, respectively). Older King radio models required a dummy load in absense of a speaker. That could affect the headphone out circuit due to internal cross linking. The KY97A doesn't typically need that dummy load resistor but I might remember some nuance based on the exact dash number on the KY97A. Again refer to manual. Some unwitting tech in the past may have integrated that obsolete requirement for a resistor. Since you swapped the unit into a different airplane that probably rules out said resistor externally but maybe something internal or the second airframe might have that resistor while yours doesn't. Did you try putting the other aircraft's radio into your aiframe?

In the end maybe a bench check would be less trouble for initial troubleshooting than all that fiddle. Used KY97A's are readily available on the open market.

If you decide to update to a neelw transceiver you might consider Garmin GTR 200, Trig brand TY91 / TY96A, or the Icom A220 with optional King slide-in adapter.

Jim
Click to expand...

There's nothing in the install manual about a resistor, but if it is serial number specific, then there may be in a different version. The shop estimated $85 for the bench test. We'll see what they say, hopefully by Monday. I was looking at that GTR 200. Looks like my best choice. I like the MGL comm, but the form factor doesnt really work with my panel. I have a Skyview, and considered the Dynon comm, but I dont want to ne stuck with an incompatable comm if I ever replace the EFIS.
 
Just to follow up, the KY97A had a bad capacitor. Avionics shop charged $294 to repair. Barely worth it for this older comm, but it is working properly now.
 
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