[GreenKeys] 28ASR slow release relay - Update

John, W9DDD w9ddd at tapr.org
Mon Aug 24 23:16:00 EDT 2020 

I finally found the rationale for the slow release in my version of 
LESU.  From P34.102 the following explanation.  Might be elsewhere too, 
but where I found it first.

"K-T Position-Using Option II
    Option II using 28G Electrical Service Unit
(1) Messages may be sent to the line from the trans-mitter-distributor 
(not monitored on the page printer). At the same time tape may be 
punched from the keyboard and monitored on the typing unit with­out 
sending to the line.

Under Option II messages cannot be sent from the key­board to the line. 
However, when sending to the line on the transmitter-distributor, and as 
  a separate operation pre­paring tape and monitoring it on the page 
printer, a break signal received from another station will operate a 
slow release relay switching the page printer to the line and stopping 
the transmitter-distributor."

I should have remembered the SR relay is frequently used as break or 
open line detector.

John, W9DDD

On 8/10/2020 8:56 AM, John, W9DDD wrote:
> Still trying to figure out the best approach for connections. (a lot of 
> the problem revolves around the fact that the TU puts out 60ma loop, the 
> default having been 20ma with the line relay involved.  Since it does 
> that by means of current limiting rather than dropping resistor, I don't 
> want to mess with that.)
> 
> LESU13 drawing tells me how I can remove the SR relay.
> 
> But, the SR relay appears to give you local copy of your tape punching 
> it the K-T position.  Do I need that? I don't know how well I type 
> blindly.  I was good on the iron horse back in the day, but I think the 
> PC has ruined my touch typing skills. No real incentive to type it right 
> the first time. Do I have a different cam with the LESU15 vs. LESU13?
> 
> One option I'm considering it bringing out a pair of wires for the 
> selector magnets, a pair for the keyboard contacts and a pair for the 
> LXD. Forgetting about all the "features", OR ...
> 
> There was a WE 63C1 (SB-6/UG) already attached to the ASR cabinet when I 
> got it.  I could use that as a way to have the normal paths be as 
> original and use patch cords to re-route?
> 
> I'm getting close to figuring things out.  Colored pencils are helping.
> 
> John, W9DDD
> 
> On 8/8/2020 3:26 PM, Jerry Murphy wrote:
>>
>>
>>
>>
>>
>> Hi John:   Does your machine have the slow release relay or are you just
>> wondering what it does?  I've never encountered one but I do know that 
>> they
>> are not necessary for the proper operation of a standard, no frills 
>> machine.
>>
>> Do you know what LESU your machine has?  The most common LESU found in 
>> ASR
>> sets is the LESU13.  I'm fairly certain that the LESU13 is called the 28F
>> LESU when used in Bell System service.  The actual and schematic diagrams
>> for the LESU13 can be found at navy-radio.com.  Here are the links:
>>
>> http://navy-radio.com/manuals/tty/wd/wd-tty-3292.pdf
>>
>> Actual wiring diagram for the LESU13.
>>
>> http://navy-radio.com/manuals/tty/wd/wd-tty-3294.pdf
>>
>> Schematic wiring diagrams for the LESU13.  Pages 1, 4, 5 and 6 pertain to
>> your machine.  Pages 2 and 3 have information on the LCXD and LBXD
>> transmitter distributors and are not needed.  The left half of page 4 has
>> information on the LAXD transmitter distributor while the right half has
>> information on the LXD transmitter distributor.  Your machine has the LXD
>> transmitter distributor.
>>
>> Take a look at the WD for the LESU7/184.  It is a no frills LESU for a 
>> KSR
>> or RO without a line relay.  Look at terminal block A inside of the LESU.
>> It shows the strapping and wire placement for connecting the signal line
>> directly to the selector magnets.  The selector magnets are wired for
>> 60 ma. signal line current.
>>
>> Here's the link to the LESU7/184 actual wiring diagram:
>>
>> http://www.navy-radio.com/manuals/tty/jh/ttyman9/drawings/2874wd.pdf
>>
>> Here's the link to the LESU7/184 schematic wiring diagram:
>>
>> http://www.navy-radio.com/manuals/tty/jh/ttyman9/drawings/2875wd.pdf
>>
>> If you remove the line relay socket and change the wiring and 
>> strapping on
>> the A terminal block so it matches the A terminal block on the LESU7/184,
>> then you should be OK.  You MUST remove the strap that connects terminal
>> C20 to terminal C21.  This removes power coming from the local rectifier
>> that went to the selector magnets when the polar relay socket was 
>> installed.
>> The C terminal strips are mounted on the cabinet above the LESU.
>>
>> On the LESU13, there is a red wire which goes from terminal 8 on the A
>> terminal block to terminal 9 of the S terminal block.  It is not shown
>> on the LESU7/184 schematic because it is not there.  It is OK to leave
>> the wire in place on terminal 8 of the A block as it has no effect on
>> proper operation.
>>
>> Check your wiring before you power up the machine.  Go over the 
>> schematics
>> carefully to make sure there are no opens or shorts in the signal line
>> wiring.  Good luck with your project.
>>
>> Jerry Murphy
>>
>>
>>
>>
>>
>> -----Original Message-----
>>> From: "w9ddd at tapr.org" <w9ddd at tapr.org>
>>> Sent: Aug 8, 2020 10:51 AM
>>> To: greenkeys at mailman.qth.net
>>> Subject: [GreenKeys] 28ASR slow release relay
>>>
>>> Anybody know the purpose of this relay?  I'm trying to simplify the 
>>> LESU wiring while still  keeping it close to standard.  I mostly just 
>>> want to bypass the polar relay socket. Never found a WD for an ASR 
>>> that didn't use the polar relay.
>>>
>>> John, W9DDD
>>>
>>>
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