[GreenKeys] WU 28ASR WIRING

[til128 at juno.com]

In the FWIW category, before making any adjustments, or replacing of parts I would clean the contacts first. Tom

---------- Original Message ----------
From: Nick England <navy.radio at gmail.com>
To: John Hargett <kg5ylg at austin.rr.com>
Cc: Greenkeys <GreenKeys at mailman.qth.net>
Subject: Re: [GreenKeys] WU 28ASR WIRING
Date: Sun, 14 Feb 2021 09:40:47 -0500


As I dimly recall, John was correct about + ground for battery systems.However I have no idea why WU grounded both the signal line and internal supply + at C2. Or why they tied the internal supply to the signal line at all. IIRC always Teletype isolated the internal supply from the signal line. My first ASR was a WU one with the 9797 - I do remember being highly surprised to find the signal line (C2) grounded to chassis - that flat won't work when you have a keyer that grounds the loop for mark (like some old tube keyers). And sparks gesparken depending on your loop topology. If your characters are OK from the keyboard, then yes I'd suspect these possibles for the LXD1. dirty/binding sensing fingers2. misadjusted transmitter - correct with the eccentric adjustment3. dirt/oil on contacts inside4. bad filter cap inside Good Luck and Have FunNick England K4NYW
www.navy-radio.com 
On Sat, Feb 13, 2021 at 10:34 PM John Hargett <kg5ylg at austin.rr.com> wrote:Getting thru my 28ASR that I got some time back.  Have it receiving ITTY now, able to also punch tape, as well as run tape.  Have a couple of questions that I am sure someone out there has more knowledge than I  ( that doesnt take too much) about these machines.  Two items I am looking at are:
1)  The LESU, which is a Western Union 9797 wiring cabinet, has the positive side of the loop supply tied to ground @  C-2 and the negative floating.  What is the design behind this?  I have looked at other LESU wiring diagrams and do not see them showing this. Would it be detrimental to put the neg at ground potential?
 
2) When I run tape on the LXD, it comes out all random and missing CR and LF .  Ran a tape RYRYRY  and get not RYRYRY on print.  Does not LF or CR at correct times.  Tape was preceded by multiple LF and CR then LTRS, Ran 40 characters RY, followed by CR,CR,CR,LF,LF, then 40 more RY followed by CR, CR, CR, LF, LF, then 40 more RY followed by CR, CR, CR, LF, LF.  What i got on type was  a couple of  over types at the start, then KCBSCCBSCCBSCCBECCBECCBSCCBER then it did a single LF and continued with the same basic characters, then did a CR and same basic characters.  
Is this a timing issue with the LXD signal generator? 
 
Dont know if it will come thru, but a copy of the 9797 wiring diagram is attached.
 
Thanks in advance
John
KG5YLG

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