That looks like the right schematic!
Nick had identified it as an early Navy unit, TT-47 (actually a TT-69, since it is a table model) and sent me to the manual, NAVSHIPS 91713, which shows the LESU wiring color codes (fig 3-3) that matches this unit.
Nick - you questioned the DC supply ("rectifier") in this LESU. In NAVSHIPS 91713, p 1-12, there is a note about an optional rectifier an it shows up in fig 3-1.
The military nomenclature plate had been removed, or I would have known where to look for documentation. I can see a spot on the cabinet under the keyboard, where a label has been removed. there is also a red inspection? stamp that looks military? See pic.
Thanks!!!
Duncan
K2OEQ
On 7/14/2025 4:36 PM, John, W9DDD
wrote:
I see you have the 3 terminal strip version, this might be closer?
From from page 3 of
https://navy-radio.com/manuals/tty/573-133-400-6404.pdf (wonder where page 2 went?)
The long rod for the power switch has a groove in the end of it that keeps it in a hole in the LESU frame. The rod also runs through a spring attached to the cradle. I usually try to wiggle the rod back and forth to get it out of the hole and leave the spring in place.
My approach would be to check wire colors on the bottom side of the terminal strips to see if they are per the schematic. A general thought is that the jumpers on the top side configure the interconnections of the parts in the LESU. (take that withe a grain of salt).
On 7/13/2025 6:16 PM, Duncan Brown 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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-- --- ---- The above comments or recommendations are SWAG. Use at your own risk. John, W9DDD