question for the "ole timers"

jim · Post by **jim** » Tue Feb 26, 2002 1:42 pm

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?

Monty · Post by **Monty** » Tue Feb 26, 2002 4:49 pm

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

jim · Post by **jim** » Tue Feb 26, 2002 7:32 pm

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!

Tron · Post by **Tron** » Tue Feb 26, 2002 8:15 pm

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

Will · Post by **Will** » Thu Feb 28, 2002 12:02 am

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).

jim · Post by **jim** » Thu Feb 28, 2002 6:12 am

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.

Will · Post by **Will** » Thu Feb 28, 2002 6:09 pm

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.