[GreenKeys] WU 28ASR WIRING

Sun Feb 14 11:16:54 EST 2021

I notice that the ground system on that drawing appears to have been 
penciled in.  But if you scan through the drawing set 
http://www.navy-radio.com/manuals/tty/wu-dwg-01.pdf you'll see many 
drawing with the terminal 2 grounded. They even did it on the Taletype 
LESU they used in some applications.

I gotta go back and check my KSR with the 9100 wiring cabinet.  At the 
time I was testing it, I was using an old TU with polar relay output. 
I'd better do some investigating before I try driving it with the TU-170.

The 9100 wiring cabinet had been butchered pretty badly before I got it. 
  So who knows.  If I find enough parts, it may get a LESU transplant.

John, W9DDD

On 2/14/2021 8:40 AM, Nick England wrote:
> 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 LXD
> 1. dirty/binding sensing fingers
> 2. misadjusted transmitter - correct with the eccentric adjustment
> 3. dirt/oil on contacts inside
> 4. bad filter cap inside
> 
> Good Luck and Have Fun
> Nick England K4NYW
> www.navy-radio.com <http://www.navy-radio.com>
> 
> 
> On Sat, Feb 13, 2021 at 10:34 PM John Hargett <kg5ylg at austin.rr.com 
> <mailto: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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