[GreenKeys] M28 - mystery LESU

[Nick England]

Huh - the Navy manual does not show a loop supply, but the referenced
2852WD does (and says LESU5/110)
I dunno - maybe they got confused back in 1953....
Nick England K4NYW
www.navy-radio.com


On Mon, Jul 14, 2025 at 3:03 PM Nick England <navy.radio at gmail.com> 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
>
>
> 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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