Author Topic: Looking for help with a 1969 Northern Electric 3 slot touch tone payphone  (Read 2472 times)

Offline Key2871

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What usually happens, is a circuit is controlled by the trigger switch, the coin operates when it passes by. That circuit in turn will allow the speech path to work.
But something is keeping that from happening, so if you operate the switches just right manually it does work(?).
But not if just the coin hits the trigger.

So is that part in the bucket next to the hopper is that the control circuit, and is it faulty.
Another important part to know, the way the phone is set up it is post pay, meaning you don't deposit a coin until the called party answers. So no coin will be able to be returned, because there is no actual relay to collect, hold the either collect to coin box if call is completed, or returned if the call is not completed.
KEN

Offline HarrySmith

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Agreed, it appears to be a simple trigger and it sounds like it is functiong properly. No need to remove it. The control circuit is the likely culkprit but I have no idea how that is set up or how to test it. Maybe one of the payphone experts will have some further ideas.
Harry Smith
ATCA 4434
TCI

"There is no try,
there is only
do or do not"

Offline mentalstampede

  • no deposit, no return
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If this phone is like the QSD3A rotary one, It's a semi-post-pay unit that is controlled by reverse  battery supervision. In normal operation, when the phone goes off hook the user already has dialtone, and is able to dial a local call direct. Once the called party answers, the battery polarity reverses, and the potted relay next to the hopper triggers, which mutes the transmitter until a coin is deposited and drops through the trigger in the hopper. The collect/return vane in the hopper is permanently fixed in the "collect" direction, and there is no relay or escrow trapdoor like in a prepay unit.
My name is Kenn, and I like telephones.

“Progress isn't made by early risers. It's made by lazy men trying to find easier ways to do something.” --Robert Heinlein

Offline Key2871

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Ok, that's what I thought so you have confirmed my suspicion. So is there any way he can defeat the mute feature? So it can be used as a regular phone, details please so he can find the terminal, wire (s) etc.
I think the original thought was to make this a pay phone that collected or returned coins. But since this has no normal collect refund relay, he can at least get it to work as a regular phone.
KEN

Offline mentalstampede

  • no deposit, no return
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If everything is present and wired correctly, it SHOULD just work without modification. Without reverse battery supervision on the line, the mute function should never activate. Unfortunately, I'm having trouble finding a wiring diagram for a QSD4B. What is the component alongside the hopper in the lower housing? If that's a simple network, then the phone is missing part of the the post-pay control components. The QSD3A normally has a control relay in that location, and the network components are contained in an external 685 type subset.
My name is Kenn, and I like telephones.

“Progress isn't made by early risers. It's made by lazy men trying to find easier ways to do something.” --Robert Heinlein

Offline rglenn

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I wouldn't think there would have been a subset.  I has a built in ringer in the bottom of the upper housing.

Offline rglenn

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Yes, that is a network next to the hopper.

Offline markosjal

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I am jealous, I want one like that!
Phat Phantom's phreaking phone phettish

Offline rglenn

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Finally got around to updating.  It is alive and on display at the Maryland Technology Museum 

Offline .....

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Finally got around to updating.  It is alive and on display at the Maryland Technology Museum

Good to hear, I have one identical to it that I'm working on as well.

Offline rglenn

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Very nice.