VIC-4 Intercom issues

[sargentwolf]

Hey all!

Having a few problems with my LMTV's VIC-4 intercom.

The mic cuts out randomly. Youll be talking, then it will start fading out and be gone. Turn off the intercom at the headset, wait a good 10 seconds, works again, but fades after a while. This happens with all of my headsets and intercom stations. Part going bad or something loose in the controller?

Second, ambient noise pickup. Its really bad. Is there a way to cut down on the wind noise? A mic foam cover perhaps?

Third, a idiot check. transformer wired into the aux in port to change the impedance in a mp3 player to military standard. Primary (2 wire) side facing mp3, secondary (more then 2 wire) side facing intercom. Correct or no?

 

[papakb]

Are you sure you have a VIC-4? A Google search doesn't turn up anything for VIC-4, only 1, 3, 5 and TOCNET.

Yes, foam balls will help over your mics.

You didn't state what the impedance of the transformer you installed is. It should be 600:8 with the 8 ohm side toward the MP3 player. You should also be adding some 10K resistors in each leg of the MP3 input side since your combining 2 outputs into one line.

Kurt
KG6KMJ

 

[sargentwolf]

Yes, the Vic-4 was used in spotting vehicles. Can use 4 radios instead of 2 like the VIC-1.

http://www.steelsoldiers.com/showthread.php?14284-VIC-4-intercom-manual-and-VIC-1-VIC-4-mods

I will correct my mistake then. Only have a transformer with no resistors. I thought I had missed something.

 

[sargentwolf]

So picked up a 500:8 ohm transformer and pair of 10k resistors. Soldered the 3.5 left and right channel wires to one 10k, the ground to the other 10k. Soldered both resistors to a leg each on the secondary side of the transformer. Soldered wires to primary side and attached to audio in on intercom.

Nothing. No sound at all. Switched it to the line in side, works.

What did I screw up? The old transformer without resistors worked, just wasnt much louder or clearer then bare wires to the phone. Now, nothing unless Ive plugged into the line in post. And with the volume cranked, its stupid quiet. like, can barely hear it with the engine off.

 

[papakb]

Put one resistor on the right output from the MP3 player and the second on the left channel. Connect the other end of the resistors together and connect that to one leg of the 8 ohm side of the transformer and the other leg to the MP3 player ground. Connect the transformer secondary (500 ohm side) to the input of the intercom and you should be good to go.

Kurt

 

[sargentwolf]

Thhhhaaaaaat is where i went wrong. I had both the transformer backwards AND the resistors soldered to the wrong parts. Whoops. This is why I break stuff for a living!

Works great now!

Back to the first question: what could be causing the mics to fade in and out?