Radio acting up

On Monday, September 19, 2016 at 3:49:03 PM UTC-4, Dan Daly wrote:
On Monday, September 19, 2016 at 12:23:09 PM UTC-4, AS wrote:
I have a question for all the electronic wizards out there. My radio is only giving a carrier signal but no modulation. I have the following set-up:
Dittel FSG71M
Dittel speaker box F10061 with two DIN connectors for two microphones (only one used)
Dynamic goose neck microphone F10039

I tried both goose neck mic.'s I have in both positions on the box.
The yellow LED on the radio turns on but no voice transmission occurs.
The power supply is provided by two 12V, 9.6Ah Lithium Iron Phosphate batteries in parallel which are rock-solid.

Any suggestion for where to start trouble-shooting?

Thanks,

Uli

Perhaps broken wires inside the speaker box (saw that on a Becker box earlier this year).

Also if booms are connected by plug, check for corrosion, and spring tension on the contacts.

Is this an installation that previously worked or a new one?

Thanks, Dan & Dan! That will get me started.
The installation was done by the previous owner and it did work just fine. Started acting up while in Moriarty this summer and seems to be intermittent. Yesterday, I was talking to the tow-plane on take-off and after the release just fine but couldn't talk to the Lear-Jet driver who called for his final in the opposite direction I was on. Fortunately, his final was much longer and I was off the rwy well before he touched down. That radio picked a bad time to act up!
Uli