[GreenKeys] WU 28ASR WIRING

[Nick England]

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


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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