[GreenKeys] Comparing td/LXD coils

[Nick England]

 Remember that 105 ohms is DC resistance but the AC impedance is much
higher. You won’t draw an amp on 115vac

The ESA Clutch Magnet Driver (CMD) says it can be set for use with
one 252M solenoid (keyboard sync solenoid) - 107-132 madc
two 256M solenoids in series (LXD TD clutches) - 124-156 madc
or one 278M solenoid (UGC-77 photoelectric distributor clutch) 36-56 madc

My solenoid chart says
https://www.navy-radio.com/tty/tty-magnets.htm
256M 74 ohms 100madc or 60vac (LXD TD clutch)

SO wire your two 74 ohm TD clutches in series and you should be all set to
run on 120vac - they are probably already wired in series.
No warranty, etc.....

The WD note says -
115V AC POWER TO BE USED ON CLUTCH
TRIP MAGNET ASSEMBLY CIRCUIT.
(256M COIL ASSEMBLIES, 74 ohm.EACH)
FOR DC OPERATION ADD SUFFICIENT EXTERNAL
RESISTANCE TO LIMIT CURRENT TO 100 M.A.

Nick England K4NYW
www.navy-radio.com


On Sun, Jan 28, 2024 at 10:37 PM Jeffrey Golas <jeffg at junknet.net> wrote:

> At the ship Im still working on a 28ASR dome top that I call "#2" (as
> theres another one next to it known as #1). I havent posted here about it
> in some time but over the last year I pieced it back together and in
> December I got it running for the first time in 20+ years. Nearly every
> single wire/harness in it was cut. We have a former TTY tech who went
> through the printer as well. I had to swap the keyboard base with another
> as its gearset and plug were both smashed. We put in a 45.5 baud gearset
> and Ive had a few QSOs with Nick from the ship!
>
> Anywhoo...as this is really a Navy UGC-48A, it used low-level signalling
> (which I also fixed), but skipped the clutch ESA as thats only really used
> with encryption.
>
> The downside is the coils in the tape reader seem to be different from a
> stock 28, in that they run about 75 ohms each instead of the 210ohms Ive
> seen in other manuals. In this unit it would have been powered by the
> clutch esa, but it would take a lot of effort to fix. I think it would have
> been 50-90v ish and likely pulsed.
>
> Does anyone know if I can just hook 120vac up to them...maybe with a
> resistor? Another 28 manual said to switch the 210ohm coils to parallel if
> running non-pulsed 120vac which would be 105 ohm and prob pull an amp.
> These Id have to leave in series to get 140ohms or so. Would that work?
>
> I confirmed the tape reader works otherwise, I just dont want to burn
> these up. Maybe its easier to just find a pair of stock coils?
>
> Jeff
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