[GreenKeys] 28ASR TD electrical question - all solved

[W2HX]

ok folks. It is a nice feeling to troubleshoot something, devise a solution and fix it.  It has been a few years since I dug inside a teletype machine.  I made the change on the centronics connector at the bottom of the TD, moving the blue wire (from the tape-out switch) from E-7 to E-6 as it shows in the wiring diagram. Then I wired this in series with the clutch magnet and control lever switch (RUN/STOP) connections. Everything now works GREAT and as intended! When the tape reaches the end, the TD stops advancing, the printer stops and the loop stays closed (no activity).

Voila! I gotta say, I wonder how many THOUSANDS of people were involved in the design, prototyping and creation of the 28ASR.  It is a crazy marvel. Every single aspect is so complex. Even the simple task I had in front of me (to get the tape out pin to articulate and then to make it work electrically) was complex and rather daunting (to me, anyway).  But alas, we have overcome!  It really makes me in awe of the real tty mechanics here on this list that have mastered all of the aspects of this machine.

Thanks to everyone's help along the way.  Next to get the computer audio into the ST6

73 Eugene W2HX

From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of W2HX
Sent: Saturday, February 22, 2014 9:59 PM
To: greenkeys at mailman.qth.net
Subject: [GreenKeys] 28ASR TD electrical question

Ok, TD is reassembled and back on the base.  What I have discovered is that no matter whether the pin is pushed in or not (contacts closed or not) everything keeps running - until I go from "RUN" to "STOP" on the main lever on the TD.

I began to trace the wiring and after several hours, I discovered that the common (orange) and normall open (blue) contacts of the spdt tape-out switch are not going to the centronics E-5 and E-6, but instead are going to E-5 and E-7!

E-7 is supposed to carry the normally-closed contact (green) of that tape-out switch (normally open means no tape present, spring relaxed, pin UP).

Does anyone know why this would be like this? It looks like it is a factory connection. Anyway, I think the path of least resistance will be to resolder to E-6 as it saysin the manual (NAVALEX 0967-LP-625-5010 fig. 5-10 and fig. 5-24)

If anyone knows anything about it let me know. I wonder if there were different versions of TD's that had this wiring differently and maybe over the years, my ASR had its TD replaced with one of another vintage.   Anyone have knowledge about the tape-out sensor working differently on different versions of the TD?

thanks again
Eugene


From: greenkeys-bounces at mailman.qth.net<mailto:greenkeys-bounces at mailman.qth.net> [mailto:greenkeys-bounces at mailman.qth.net]<mailto:[mailto:greenkeys-bounces at mailman.qth.net]> On Behalf Of W2HX
Sent: Saturday, February 22, 2014 6:15 PM
To: greenkeys at mailman.qth.net<mailto:greenkeys at mailman.qth.net>
Subject: [GreenKeys] 28ASR TD question

Hello all,

Things are getting exciting around the shack here as I get the ST6's and computer and radios wired up. I decided to try to fix a long time problem on my TD on my 28ASR.  The tape out mechanism was always "pushed in" so it would never recognize the end of a tape. The printer would keep running after the tape was done.  So I decided to do something about.

Well, what an odyssey.  I finally found some little lever, deep inside the TD that was wedged back. I pushed it forward and it released, putting more tension on a lever that pushes the pin out.  So as of now, I have the pin with a good amount of tension on it and it pushes in and releases back out fine.

My question is about the electrical contacts that this pin actuates.  There is only one pair of wires coming of the switch.ICan someone tell me if these contacts should open or close when the pin is pushed in?  Once I get this answered I will (attempt) to reassemble everything and put it back together.

thanks in advance!
73 Eugene W2HX

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