Ernest COCOT phone help...

[thatsmanjear]

Hi there, first time into the Payphone world...  I acquired a NOS Ernest COCOT payphone, pristine, absolutely beautiful, still in plastic, had keys.  I want to get this working on standard POTS line for my father-in-law who was a lifetime career AT&T/Pacbell man.

The PCB in the Ernest is a "Model D3", so I went looking for documentation and found a manual for Ernest model ETX, but it's not clear as to whether ETX is referring to the whole unit, and it contained a variety of PCBs (model D3 being one of them), or whether ETX is a PCB and different altogether than D3.  Anyway, I proceeded with the assumption that ETX is similar if not the same because the description of ports, connectors, terminals and PCB is spot-on...but no pictures in the manual so can't compare.

First thing I did was remove the dead 3.6V battery that was soldered to the PCB (it was dead), and replaced with a holder for a 1/2AA 3.6V battery.  I read on a forum that if the battery was dead then no dial tone.

Next, I connected up red (ring), green (tip) and yellow (gnd) from my pseudo-POTS, a Ooma Telo, and measured voltage and current.  When on-hook, getting 50V, and can draw 28mA, which is within spec according to the Ernest manual (42V-56V, 20mA-90mA).

I then "called" the payphone, and the ringer rang, loudly I might add

...BUT, I get no dial tone when I lift the handset!!

So I then thought I would probe the PCB, and it turns out that none of the TTL logic chips are getting any voltage.  I was expecting normal 5V inputs to all the TTL chips, but there's nothing.  The PCB has 10 electrolyte caps, which at 30+ years might be bad, but none are bulging or leaking.  I checked the diodes on the portion of the PCB that looks like it would handle voltage regulation, and they all check out good.

I've tried it with the coin switch and relays unplugged from the PCB, just in case.  Tried it without the bell, no luck.

Any ideas on what to check next?  I appreciate any help, or pointers to more documentation or forums that could prove helpful.  I've spent a few days really trying to google things so I'm not asking easily found answers.

Thank you!

[HarrySmith]

Welcome to the forum. I am sure one of our payphone people can help you but I am not one of them

I do know pictures of everything would be helpful.

[thatsmanjear]

Thank you.  I meant to attach the PCB pictures, here they are.  One picture is the full PCB.  The other is focused onto what I think is where the power is regulated, and I think that may be where the issue is, but I don't have the knowledge to troubleshoot it.

[thatsmanjear]

SOLVED: It's working!! Seems it is VERY sensitive to the amount of current that can be supplied by the battery (and probably capacitors helping it). I had replaced the existing soldered battery with one that was same voltage but less current. So on a whim I installed a higher-draw battery and replaced all the capacitors (they measured fine, but just in case) and it's now happy as a clam. Now I need to reprogram the rate tables...it wants $2.40 for me to call my own number, lol.

[thatsmanjear]

Mounted in the garage and fully operational, all calls $0.25 (coins in tray mounted beside in case you're a little light).

[Ernest-O]

Congrats on getting the D3 working. I, however, am having a little trouble and was hoping you could provide a little guidance. I have a NOS Ernest D3 as well, changed the battery and the phone fired right up. Draws DT at 48vdc and rings when called. Trouble is the rate, I'm at the deposit $2.40 stage and would like to program the rate tables and configure the other options. I ordered a PCB based on a design posted on facebook (https://www.facebook.com/photo?fbid=9919364854827330&set=pcb.10025804344193402) and added a resistor, cable, and lcd. When I go into program mode the screen lights, then goes off. The pcb was stated to work with the etx and d7, d3 wasn't guaranteed. I was wondering if you knew the pin-out from the PCB socket to the LCD, I have seen videos stating the pin-out isn't 1 for 1 but cannot find any information on  how to connect the LCD to the ckt brd in the phone. Any help would be fantastic, I'm trying to get it working for a local museum who acquired their towns last phone booth and wants to create a working phone both to teach the kids about the era of the payphone...