[GreenKeys] M28 - mystery LESU TT-47A/-69A

[Duncan Brown]

Nick,

FYI,

Just getting back into this machine.  The wiring of my TT-69A matches 
the schematic (fig 2-79) & wiring (Fig 3-3) diagrams of NAVSHIPS 91713, 
but not 2852WD & 2852WD, rev D. (maybe they did in earlier versions?)

My TT-69A & NAVSHIPS 91713 do not have the polar ("LINE") relay and the 
signal line filter connects directly to terminals C5 & C10 (TB-751).

Thanks,

Duncan,
K2OEQ


On 7/14/2025 3:03 PM, Nick England wrote:
> Seeing the cloth-covered wires made me think it was an early model. I 
> have a TT-47A with a LESU that looks very similar except no loop 
> supply which looks like a ham add-on.
> The TT-47A LESU is Navy model SB-154A. Teletype model LESU5/103
> Manual is at
> https://www.navy-radio.com/manuals/tty/tt47a-91713-5207.pdf
>
> Wiring diagrams 2852WD and 2853WD are in 573-100-400
> https://www.navy-radio.com/manuals/tty/573-100-400.pdf
>
> Nick England K4NYW
> www.navy-radio.com <http://www.navy-radio.com>
>
>
> On Mon, Jul 14, 2025 at 1:59 PM Duncan Brown 
> <duncanancy at earthlink.net> wrote:
>
>     I'm checking out a M28KSR that looks like it has had some major
>     rewiring done to it.
>
>     All the jumpers that are normally on terminals 4-14 of the cabinet
>     terminal blocks have been removed.  There were two, 4 conductor,
>     external cables connected to the cabinet terminal block, all
>     unterminated, except for a 2k power resistor (loop current
>     limiter) connected across  C10-C11.
>
>     I see no designator on the LESU and the color codes of the cable
>     from the LESU to to c5 - c14 do not match the colors I see on
>     2874WD (or any others).  The LESU has what looks like a Line Shunt
>     Relay, a 120VDC power supply (with monitor jack), a Motor-Stop
>     relay and an 120VAC input panel ( lamp switch & fuses). See
>     picture enclosed.
>
>     Can anyone identify this LESU?
>
>     I tried to remove the LESU by removing the big screws. The LESU
>     was loose, but would not come out, apparently because of the front
>     panel power switch extension mechanism.  I expected it to
>     disengage when I lifted up the LESU, but it did not.  Is there
>     something in the switch extension mechanism that has to be
>     removed/released?
>
>
>     Thanks,
>
>     Duncan
>     K2OEQ
>
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