Batboard

I have a tone remote desk unit-model #T1601AM that lost receive audio. The XMT audio to the phone line is okay. Anyone remember anything about these? Anyone still have schematics?

Hi:

Well, I know the model !

I probably have the diagrams if you
are not in a hurry.

You probably have lost the Audio Power
Amp....When connected up wrong, they do
tend to smoke

MS

I don't know old this unit is, but I am assuming its at least 25 years old. It was moved to a new location in the building about 3 years ago and shortly after that, the audio went out. The department never did anything with it, as they operate on UHF and this is a lowband remote. They now run mutual aid for another department and need this radio. I had an amplifier on the phone line and the tones and audio out is fine. It's just the amp that drives the internal speaker. There are 2 transistors in the main audio PA- one a PNP and the other an NPN. One of these has 13.4v B+ on the base and the other doesn't. I'd like to have a schamatic before getting any farther into this. None of the other techs around here have ever seen one of these, which tells me they're all around my age!

Maybe the IC module that drives the audio PA stages is bad ( and obsolete--but they had a retro fit kit for them awhile back ).

Tron

Also double check the mic wiring as the audio for the speaker passed thru a normally closed contact in the mic ptt switch, to mute the speaker on the remote and allow the other extension desksets/mic/speaker(s) to have a "intercom" audio. Also the volume control goes bad, it is a speaker pad, 20 ohm pot.
Check at "Audio A" screw connector with a high impeadance meter or the monitor mode on your butt set for receive audio. (I think I have fixed TOO MANY of these, it sticks in my mind).

Will, which terminals on this unit do the two NC mic wires attach to? There are two NC wires from the mic that are not connected to the unit- just the ground, PTT and audio are.

Screw term 13 is 8ohm audio speaker HOT NO volume control. Term 14 is 8 ohm MUTE.
Make sure that there is continuity between 13 and 14 with the mic NC switch.