[GreenKeys] 28 Stock Ticker Printer diagram

[Chuck Rehor]

Great job with the PCB diagram, Peter! I love looking at how things work in
detail.
I noticed a few parts didn’t have values like R5 and R15 pots, and Cp1 cap.
Just an fyi. I also thought it was curious that the resistor feeding the
pot was 5W. I didn’t think carbon pots could handle high power like 5W
unless it was wire wound. Or maybe I’m completely off-base.
Chuck Rehor
W9CFR

On Fri, May 9, 2025 at 8:55 PM Peter Gottlieb <hpnpilot at gmail.com> wrote:

> After a design review meeting this afternoon which had much more
> mechanical than electrical, I decided to reverse engineer the PCB and
> wiring in this model 28 stock ticker strip printer.
>
> I think I understand what's going on.
>
> I saw in one of the documents it uses a bipolar signalling scheme and
> the diagram bears that out.  There is a bistable mercury polar relay on
> the board.  All transistors are germanium. I was surprised that the
> selector magnets are driven from a 25 volt supply; they must be
> relatively low inductance?
>
> I'm not sure if attachments go through this list but if so I included
> what I drew from my little exercise.
>
> Initially I thought maybe the 1/4" jack was the input but that is not
> the case.  The input is via a terminal block.  I tried applying 10 volts
> and the selector pulled in.
>
> Which led to a problem:  something seems locked up as what looks like
> the main clutch is just clicking and nothing past it turns even if I
> release the selector magnet.  I can turn the motor by hand to see where
> the clutch releases so don't need to run the motor.  I wonder what is
> going on.
>
> At least I have the electronics figured out.
>
> Peter
>
> P.S., if the diagram doesn't make it through, give me your email address
> and I will send it to anyone who wants it.
>
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