Need help with pair of sound powered phones. newb

[classic360]

I bought a pair of United States instruments corp type-333 sound powered handsets, from an estate sale for $10.

They don't seem to work, if any of you could point me in the right direction I'd really appreciate it.

If I understand how sound powered phones work even not connected to each other they should at least have sidetone, I tried wiring the 2 phones together with no luck either.

I continuity checked all the wires and switches and they are fine.

I polished the contacts where the microphone/speakers go, still no luck

Also I tried connecting my multimeter to the microphone/speakers and talking into them and seeing if any voltage was generated, none was.

thanks for any help.

[dsk]

Welcome to the forum!

I have used 2 other makes of sound powered phones, mainly the transmitter and the other ends receiver are just connected together.

One system were connected with 3 wires. one common, one connected to one end transmitter and other end receiver. The 3rd to speak the other direction. (in addition it was an audible signalling unit)

The more common are like the TA-1  (You may find lots of info by googeling TA-1/TP)  as this: http://radionerds.com/images/2/22/TM_11-5805-243-13.PDF

The diagram on P 42 may be good.

Just connecting 2 and 2 elements together, they should both work as transmitter and receiver.

Putting all 4 in parallel should also work, but the signal may be weaker.

dsk

PS applying just a little voltage e.g. on/off with a small battery 1.2V  or... will generate a loud click!
DS

[classic360]

Thanks for your help, one of the handsets does work. 


But the the emitter and receiver in the other handset are dead.
Is there any info on repairing them?
I did a few searches on here, but since I'm a newb I don't really know what I'm looking for.   

They don't transmit, receive, or make a click when I apply low voltage like the ones in the other handset did.

[dsk]

Maybe some dust, or particles has blocked the moving parts?
Maybe the electromagnet is broken, The permanent magnet...
(Actually just a lot of guessing)

Maybe this picture may help?

dsk