APX7500 Audio issue

[lukeboedeker]

I am working on an interface between an apx7500 mid power and an aircraft audio panel. I am using an o3 handheld control head.

I am having trouble getting any audio at all audio out of the apx while it is connected to the interface cable that I built. My cable has been completely checked out and verified that all connections are good and to the correct pins. I checked the radio with a standard Moto speaker and speaker/ign sense cable and it works perfectly.

Just as I ran out of time to work on it tonight, it occurred to me that I don't have pin 14 and 15 jumpered in my connection cable to the audio panel. Thus the radio was possibly powering up in emergency mode.

Does anyone know if somehow emergency mode could be muting the speaker output ? It is a factory default codeplug.

Any other ideas? I'd like to not waste any more time on this issue, I need to get this installation working ASAP, so if anyone has thoughts I would appreciate the help!

 

[steve_jacobson]

J100 Pin 15 EMERGENCY: Input used to detect emergency activation. This pin must be connected to ground (Pin 14) by a cable if emergency is disabled, even if disabled by CPS. If enabled, this line must be grounded via a switch, which is normally closed.

 

[lukeboedeker]

I read that last night as well. I powered it up on the bench this morning with the emergency pin un-grounded and it doesn't seem to have any effect on the audio output. Back to the drawing board.

 

[wd9cms]

Do not know if this will help...make sure that you are not grounding the audio output from the radio if you are connected to speaker output. I do not know what audio panel you are using but you may want to get receive audio from RX_FLT_AUDIO. This is low level audio which might work with the audio panel. Just some ideas....

Bill

 

[lukeboedeker]

Thanks for the idea, Bill. As it turned out the audio panel liked he RX_FILT_AUDIO much better than speaker audio. Apparently the impedance mismatch was too excessive for the audio panel circuit with he higher output power of the speaker line on the APX. I have interfaced lower tier radios for years using the speaker output for rx audio, and it always worked well even though there is an impedance mismatch. The audio panel is a PS Engineering PAC24.

 

[motorola_otaku]

Just curious, are you using the rear accessory connector or the DB25 on the TIB?

I actually had a defective TIB cross my desk once that wold not output speaker audio at the DB25. Everything else worked fine. Something to watch out for in the future...

 

[wd9cms]

I am glad that the RX_FLT_AUDIO worked with the audio panel. I was wondering if it makes sense to add the external speaker for the cabin if its a Public Safety aircraft. I am not sure if the speaker audio floating with no load can cause a problem. I would like to see your installation when complete. if possible, please send pictures.

Thanks,

Bill

 

[lukeboedeker]

 

[lukeboedeker]

Ops check good today. I've left the speaker leads floating and so far no negative issues there. It is in an agricultural aircraft. AES256 direct line to my office is pretty cool. The competition will have to get their inside info elsewhere!

 

[wd9cms]

That's Awesome! I like the O3 HHCH because it takes up very little space. Looks great in the airplane.....

Bill