[GreenKeys] 28 TD questions

[gil smith]

Hi Jack:


At 06:57 PM 1/21/02 -0500, you wrote:

>Gil,

>All 28 TTY keyboards and TD's have the "signal generator" box. The
contacts

>are actually a small "T" shaped toggle. You are only interested in the

>contact that's normally-closed (mark). I know you digital/computer 
guys

>would probabaly have to use a scope, but a good old VOM can tell you
what

>you need to know (want to borrow one?...hahaha!).

>I looked at the pictures and I would advise you to open up the little
sig

>gen box to make sure the contacts aren't gold-plated. They will not take
the

>HV 60 ma. loop! If they're gold plated, you'll have to drive the loop

>through your 232 board. 


I opened up the can, and found an inner can (insulated from everything
else, but connected to the shield of the data cable).  Inside the second
can, I found a little pc board with two resistors and a cap for contact
filtering.  Under that I found the T-shaped gizmo and the mark/space
switches.  Only the mark switch is connected, and the contacts are indeed
gold.  A low-voltage tempest machine I suppose.  That's ok.



>Not sure what the little PC board is that sits over

>the coil...never saw that before. 


That board was another little RC filter, for the RUN switch contacts.



>I would assume the TD has some TEMPEST

>wiring based upon the three-pin connector. It's the same connector on
the

>UGC-77's that a lot of us got off Ebay. 


It looks like mating connectors are about $20 -- I think I'll just  run
another cable from the can to unused screws on the terminal block.



>It would probably be a safe bet that

>the coil is 115VAC since the machine has an AC motor and it's Navy. If
you

>can see the pole-piece, look for the "D" ring that would tell you it's
an AC

>relay/coil.

>I'll try to dig out the pinouts of the connector on the bottom of the
LXD.

>By the way, you typically wire the "STOP-RUN" switch, the "6th pin"
that

>senses the tape has run out, and the "tape jam" lever in series with
the

>coil. So, aside from a few jumpers, you should only have the AC for 
the

>motor/solenoid going in and the two wires for the loop going out.


I finally traced out the unit's wiring:  two solenoid coils wired in
series (about 150 ohms) are brought out to the terminal block on
positions 1 and 2 (3 is cable shield).  The RUN switch and the TAPE-OUT
switch are wired in series, and are brought out to the terminal block on
positions 5 and 8 (4 is cable shield). 


If the solenoid is wired in series with these switches, it must be a
low-voltage solenoid -- the filter cap on the run switch is only rated
for 50V.  So what voltage should this solenoid be run at?  It pulled in
easily with 15VDC (even down to 8VDC).


 I'll continue this wiring discussion on Bob McConnell's email.

<bold>

</bold>

>I was bidding on that TD and forgot about it. Did you get it from
someone in

>Hawaii?


I got this about a year ago on ebay -- not from Hawaii though.  I've seen
two or three on ebay over the last couple of years.


gil





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