[GreenKeys] New to me Model 28 and needing assistance

[SK Campbell]

Happy New Year everyone! 
I have been a GreenKeys subscriber for some time and really enjoy reading
the messages daily. Always great and informative!

This is my follow-up and update message from October when I started
restoring a handsome Model 28 KSR unit. First things first, a big thank you
to the many GreenKeys members helping me with my questions and concerns with
this special machine: especially Nick England (K4NYM), Jim Cooper (W2JC),
John Koster (W9DDD), and Jerry Murphy.

A very special thank you to Paul Cembura (Mr. RTTY) for his parts,
suggestions and real-world operations with Teletypes from the past. Always a
pleasure talking with him. 

I have the unit working with my HAL-5000 and copying ITTY with no errors;
the next step will be interfacing it with my vintage Collins S-line setup
and/or my ICOM 7100 (set-up as a desktop). Any suggestions with those
separate arrangements, please feel free sharing with your suggestions. The
only issue I need to fix is the signal bell, which someone disconnected
including removal of the stunt box switch, wiring and upper case "S"
function bar (Mr. RTTY is working on those part requests for me).

I am now in the market for a standalone LDX (60 wpm) and Reperforator (60
wpm) and will gladly pay costs and shipping. Mr. RTTY has my request, as
well.
Here is a short video of the Model 28 copying ITTY and sounding like a happy
1970's machine:
https://youtu.be/osJZDypBMfU

Thank you all for the helpful and continued information. I am so glad there
is a great resource for this vintage historical equipment.
73,
W7SKC
W7SKC1 at gmail.com <mailto:W7SKC1 at gmail.com> 
campbellsk at comcast.net <mailto:campbellsk at comcast.net> 

Steve
		_____________________________________________
		From: SK Campbell <campbellsk at comcast.net> 
		Sent: Thursday, October 7, 2021 14:21
		To: GreenKeys at mailman.qth.net
		Subject: New to me Model 28 and needing assistance


		I have been a GreenKeys subscriber for some time and this is
my first attempt generating a message seeking information and guidance from
the experts. I have acquired a nice-looking Model 28 KSR from Wayne
(WB4OGM). Thank you, Wayne!
		With assistance of Nick England (K4NYW) and his Navy-Radio
website, we suspect the unit had a life with the Army, which was unusual
since they mainly used Kleinschmidt's. 
		It has the following components:
		.	Typing unit, MX-3311/UG, LP 77 YD AGM
		.	Keying unit, LK 25ARN, Stunt box AEP (WD 3047?)
		.	Cabinet, LAC 203
		.	Motor unit, LMU 3. The motor intermediate and pinion
gears have part numbers for 60 wpm. (I have an extra set, verified via part
numbers for 107 wpm.)
		.	LESU 42, WD3716 (Nick suggested that the TT-243/FG
is similar, since I could not find the WD on the Navy-Radio site for the
LESU 42, I did find a TM on eBay). Fortunately, or unfortunately, the unit
appears to have been heavily modified for other service, because the LESU
equipment does not match the original specifications. There are solid-state
devices underside of each LESU sections. (I have not tried reverse
engineering the motor control, shunt and line relays or the DC source
sections of the LESU, yet.)
		I have made a cautionary power up with the unit and the
"Maintenance Light" works as advertised, however, no joy with the motor or
typing unit with the "Normal On" and main power switches on. After some
serious wire tracing, resistance and voltage checks, I believe the unit
could fire up. I have tested the motor and it does run. And I cleaned the
contacts on Ji/P1 and J2/P2.

		The signal path from TB 1 (back of cabinet terminals 5 and
15) route through the signal network on the bottom of the cabinet to two RCA
jacks (labeled "keyboard" and "printer"). The motor control component on the
LESU has one lead to the same location on the bottom with its own RCA jack
labeled "motor". I believe this is the main motor control lead for the start
relay, etc. With caution, I added a 100-ohm resistor to the tip and sleeve
of the "Motor" RCA connections and the motor starts and runs without any
apparent issues. The unit appears having a satisfactory current loop (not
running open) and the red keys are operational, however, the green keys are
not responding. (The keyboard is mechanically unlocked with the red key
"UNLK"). The code bar and transfer levels indicate the correct alphanumeric
key when pressed.
		I have measured approximately 143vdc on numerous terminals
of the main TB1 (back of cabinet), I suspect for the local loop voltage. 
		Resistances to ground (RCA jacks):
		"Keyboard" = open
		"Printer" = 55 ohms
		"Motor" = open
		Voltages to ground (RCA jacks) Normal power ON:
		"Keyboard" = 2.6 vdc
		"Printer" = 3.3 vdc
		"Motor" = 7.0 vdc

		My expectation is to use an acquired HAL 5000 as a
demodulator and interface the Mod 28 and one of my vintage radios. Again,
before I heavily modify this unit back to semi-stock operation for amateur
radio use, I wanted to ensure it is mechanically sound and functionally
operational.
		Since I do not want to damage any components, I am seeking
any and all guidance and information on moving forward with least amount of
consternation, on possible interface connections, testing and
troubleshooting. Was this unit used with a PC and software, e.g., MTTY or
similar? I do not know.

		My experience is limited; however, I have worked with a
Kleinschmidt and built a TU for it back in the 70's and always wanted to get
back into RTTY. During my telecommunications career, I was assigned to the
toll test board department and TOC (I really enjoyed that work), where we
used Model 28s for monitoring and testing of local loops for the USAF, NWS,
and law enforcement; any TTY mechanical issues went to the local
private-line repairman. Recently, I have watched numerous RTTY YouTube
videos (Marc and Ethan) and have gained a greater understanding and
extremely thankful that GreenKeys is so active and a positive resource!

		Thank you all, in advance.

		Steve W7SKC
		W7SKC1 at gmail.com <mailto:W7SKC1 at gmail.com> 
		campbellsk at comcast.net <mailto:campbellsk at comcast.net>