[GreenKeys] New to me Model 28 and needing assistance

W2HX w2hx at w2hx.com
Sat Jan 1 20:25:43 EST 2022 

Wow. A real beauty. Was it a repaint? Looks great.

73 Eugene W2HX
Subscribe to my Youtube Channel: https://www.youtube.com/c/w2hx-channel/videos



-----Original Message-----
From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net> On Behalf Of SK Campbell
Sent: Saturday, January 1, 2022 1:51 PM
To: GreenKeys at mailman.qth.net
Subject: Re: [GreenKeys] New to me Model 28 and needing assistance

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> 


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