Archer intercom

[KevinW]

Does anyone happen to know how the old archer wired intercoms transmitted?
I don't see any kind of mic on the board.
I just replaced all the caps and have it working on the receive side of the master control, I can page with the buzzer but don't have voice transmit to the satellite units.

 

[Wade Hassler]

The speaker might be the microphone

 

[gophert]

Does anyone happen to know how the old archer wired intercoms transmitted?
I don't see any kind of mic on the board.
I just replaced all the caps and have it working on the receive side of the master control, I can page with the buzzer but don't have voice transmit to the satellite units.

View attachment 115548

Yup, the speaker was also the microphone.

 

[Nigel Goodwin]

Yes, common practice, the speaker was used as a microphone.

 

[KevinW]

Ok, thanks for solving that mystery.

 

[dr pepper]

If your not transmitting voice audio but receiving it try cleaning the contacts in the talk/transmit switch.

 

[gophert]

If your not transmitting voice audio but receiving it try cleaning the contacts in the talk/transmit switch.

The speaker needs to be fairly stiff to work well. The fiberboard May have become quite "soggy" over the years which means they move a bit but the audio power of your voice may not be transmitting to the voice-coil of the "microphone" to generate a signal. A thin layer of varnish can crisp them up.

Alternatively, potentiometers fail as well so check if the pot has a dead spot. Replace or try spraying with "de-ox it."

 

[KevinW]

Thanks for the input, it was the capacitor in the upstairs unit.
Two problems, one in each unit.
All there is in the satellite unit is a switch, speaker and capacitor.
When I tested the cap it had a 10% failure.
I was running out of things to test on the main unit so I took the basement unit and wired it to the main unit at the bench, it worked which pointed me in the direction of the upstairs unit.
Everything is back up and working.

 

[picbits]

I used to sell these in Tandy many moons ago - great bits of kit for the £10 we charged for a basic system.

 

[KevinW]

Great bits is right! Such simplicity and reliability in a small package, well worth repairing.

 

[Nigel Goodwin]

Great bits is right! Such simplicity and reliability in a small package, well worth repairing.

I'm still using one I've had for years, can't remember what make it is as it doesn't say - but I've certainly had it more than 30 years, it's never failed, and I can't say I can remember ever changing the battery?, but I suppose I must have at sometime?.

Seeing as it's sat about a foot away from me I've just popped the bottom off, it has a Duracell battery - so I must have changed it at least once. The date on the battery is 2008, and they have long use by dates, so presumably it was fitted around 2003? - still going strong, and probably only the second battery it's had.