A technology museum curator asked me to try to get his NE 3 slot payphone working for museum display. So far most everything works except dialing out. The phone can receive calls and the receiver and transmitter both work.
My problem is, the keypad doesn't produce tones. While a button is pushed, the dial tone gets softer but the dial tone is not broken.
I will upload some pictures. Thanks in advance for any ideas.
Rick
Did you try swapping the red and green wires?
Early TT pads were polarity sensitive. Later pads used a polarity guard.
Yes, I was going to say that. But my phone froze and tooted.
Also it could be a mis wire that's keeping it from working.
Or the dial is bad.
Yes, I switched the red and green, no change.
another observation, the dial tone gets louder after inserting a dime or quarter.
Well I'd say it's the dial, it's gone south.
That is a semi postpay pay station. The dial tone and transmitter will increase in volume after coins are deposited.
try cleaning the tone pad contacts and see it it will produce tones.
I don't know the number on that dial, but I remember northern tone dials were a darker grey. I have one from a northern business set, that could be wired into that, free just cover postage. The dial is new with documentation for connecting it up.
Ken, that's awesome! How would you like me to handle the payment?
Sorry I meant to say send me a PM and we'll work it out.
Edit,, thanks Rich I'll let you know when I send it out.
Ken
Rick
You might want to try this before you get involved installing an unknown Touch Tone pad.
1- Remove the front of the payphone.
2- Connect a clip lead to the screw that the orange/black lead coming out of the Touch Tone pad is on.
3- Connect another clip lead to the screw that the red/green lead coming out of the Touch Tone pad is on.
4- Using ANY PHONE, unscrew the transmitter cartridge and clip the other ends of both
clip leads to the transmitter contacts in the handset.
5- Push a few buttons on the payphone's tone pad. If no tones are heard reverse the
contacts in the handset the clip leads are attached to.
6- If you hear tones try calling a number using the payphone's pad connected to the
handset.
This will tell you if the pad is actually working or not.
I wouldn't assume the pad is bad. That's a postpay 3-slot that depends on polarity reversal
to function. Could be other problems with polarity in the payphone causing the pad not to produce tones.
See pictures.
Have fun!
Stan S.
See photos.
Good to know, I knew someone would come in and give another idea to try. Thanks Stan.
Thanks Stan, I'll give that a try.
Ok, I followed the steps but did not get tones from the pad even when reversing the contacts.
I did use a rotary phone in step 4 which I assume was ok.
Yes correct, you just need to verify that you get tones or not.
Ken
You probably already know this but just to be sure you have to unplug the front of the payphone from the lower section.
You should hear tones coming out of the handset of the phone you connected the pad to.
If you aren't getting tones the pad is shot.
Stan S.
Ken
Just to make sure.
You do know that the rotary phone you're using must be plugged into a phone line
and you should get a dial tone when you take the handset off hook that you're connected to.
Then check for tones.
Stan S.
Yes, of course otherwise your not going to get a real status.
In other words, no power no tones, or dial tone.
I was assuming that power was applied to the test phone as well as the pay station set.
You did do that, right Rich?
Ken
Meant to address that to Rick.
I'm sure you know.
Stan S.
Thanks guys. Yes the rotary phone had dial tone during the test. I will run the test again ensuring the upper chassis is disconnected as I can't remember if it was during the first test.
Rick
Usually you can't leave the upper connected to the lower housing. Because the cable won't reach.
But yea go ahead and rerun the test and get back with us here.
So I need to have power to both phones to do the test?
Rick
No!
The only phone that should be powered is the rotary phone you're connecting the payphone's front to.
The two connections from the rotary phone power the TT pad.
The tones from the pad (assuming there are any) are sent into the rotary phone from these same two points.
Stan S.
Ok, then I did it right, and I have no tones. Ken, looks like I could use that dial after all.
It's still here.
Payment mailed today - thanks!
Its ready and waiting, I'll shoot you a pm When it goes.
Good luck.
Thanks Ken.
I'm always willing to help museums, so glad to be part of it even in a small way.
I'm glad that dial cured your dial problem, Rich.
Well, I know the dial works but I could use some guidance on the wiring. The Dial it is replacing (NE35E3) has 8 wires of which 7 were connected to either the terminal or network. The new dial (NT3503L2) has 4 wires (the directions describe 6 with 1 not used)
Ok, I got the dial installed and through process of elimination, got it to dial. Currently everything is working except the transmitter. The pay phone caller can hear the called party but the called party can not hear the pay phone caller. I could have the dial wired wrong. I also found some information on post pay phones indicating the transmitter is intentionally shorted until coins are deposited. Depositing coins doesn't enable the transmitter.
Suggestions welcomed.
Check the handset by connecting it up to another phone, to eliminate or confirm that the transmitter is working.
I don't see how the dial would have any bearing on the transmitter not working. You can try reversing the transmitter wires on the network, but I again don't think that would effect the transmitter.
And connect a known working handset and try that.
Ok, thanks.
On some of these sets, the transmitter was muted unless the hopper was triggered by a coin. It could be what's happening with yours. So if you try another handset and the problem persists, trigger the hopper switch with your finger go from there.
Also, hot water an a strap wrench will work to get the handset caps off. That's what I had to do with my Northern.
Well, I tried another handset, same issue. Then I tried your finger on the hopper idea and as I depress it, I can hear the audio from the called party but for only a moment. Holding it all the way down doesn't maintain the audio. I have to catch it just right but am able to reproduce it almost every time. I feel like I'm getting close but am not sure what to do to bypass this switch/connection?
Have you tried reversing the polarity of the line cord (Red and Green)?
Yes, no change. I thought it would stop the dial from working but didn't.
What's that picture of? I've not seen anything like that before.
Here is a wider shot. The blue arrow is what I am pressing down to get the audio to work briefly.
I assumed that was the hopper switch you mentioned.
That must be a post pay set up. I've never seen that before.
So there must be something that triggers when the coin passes, that's not triggering to allow voice.
Since I've never seen that setup I don't know what to say. There must be someone here who knows about northern post pay set up?
Can you pull that part out & get a picture of the other side that shows the wiring? Looks like ony 1 screw holds it in?
I'll take a look and post a pic shortly - thanks!
Appears to be held on by 3 screws. I can remove if helpful but I think I got Pics of all the wiring.
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.
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.
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.
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.
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.
I wouldn't think there would have been a subset. I has a built in ringer in the bottom of the upper housing.
Yes, that is a network next to the hopper.
I am jealous, I want one like that!
Finally got around to updating. It is alive and on display at the Maryland Technology Museum
Quote from: rglenn on July 04, 2020, 07:58:15 AM
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.
Very nice.