[GreenKeys] Model 33 Keyboard

[PJ Bennett]

Doug, do you have a source for NOS contact block plastic parts?  I have a
keyboard from a model 33 that has a broken tab on one end.  I glued it with
super glue, and it seems to be holding ok, but I'd really like to replace it
if possible.

Thanks,

PJ

_____________________________________
 PJ Bennett, BSEE
 918.704.7055 | pj at pjbennett.com | pjbennett.com



-----Original Message-----
From: Jones, Douglas W [mailto:douglas-w-jones at uiowa.edu] 
Sent: Tuesday, January 19, 2016 1:46 PM
To: Michael Zahorik <m.zahorik at sbcglobal.net>
Cc: GreenKeys at mailman.qth.net
Subject: Re: [GreenKeys] Model 33 Keyboard

On Jan 19, 2016, at 1:03 PM, Michael Zahorik wrote:

> Correct me if I'm wrong. I believe that the keyboard works as follows.
> 1. the user presses a key
> 2. the key lever pushes down some code bars 3. some the code bars 
> transfer and trip the Universal lever.
> 4. the universal lever allows the contact bail to rotate and allows the
contact wires to work.
> 5. Here I'm a little foggy, I think that the contact wires present a
parallel representation of the key to the distributor. Not sure how the
distributor knows when it should work.

Right.  The universal lever rotates the H-plate (really X shaped) that pulls
an extension lever that goes under the typing mechanism back to the
distributor.  Pulling that lever trips the distributer clutch to convert the
parallel data to serial form.  At the end of its rotation, a cam on the
distributer pushes back on the universal lever, resetting the keyboard.

> 6. the distributor converts the parallel code into serial code.
> 7. once the serial code has been sent then the Universal lever is tripped
and the contact bail opens the contacts wires. Also not sure how this works
either.
>  
> Next I tried to measure continuity of the contact wires to the J7 plug. I
got nothing, all open or very high resistance. Looking at the right side
contact wire assembly, I found the that the lugs connecting to the terminal
bar were badly corroded.

On -33 I am restoring, the plastic body of the contact block had some broken
tabs, so we bought a new-old-stock replacement and then carefully mounted
the contact bars and wires on it.  That was tricky, we took close-up before
and after photos and compared them carefully in order to make sure all the
bits were in the right places.  The best of the photos are here (the contact
block discussion is after a discussion of power supply wiring):
-- http://www.cs.uiowa.edu/~jones/pdp8/UI-8/log2015a.shtml#2015-01-30

> I also found that one of the terminal bars was loose. See picture. I can
either clean or replace the lugs and I figured I would glue the small
terminal bar back onto the terminal assembly with epoxy. Any thoughts?

As I said, we replaced the plastic block.  NOS parts may still be available.

> Also how should I clean the contact wires and terminal bars?

Soap, water and a toothbrush isn't a bad place to start.  I wouldn't
recommend any heavy abrasives.  Perhaps this is a good place to use a
contact burnishing tool (see the recent thread on that subject), since
that's going to have a lighter touch than any other abrasive I can think of.

If your assembly has rusted, the 12 springs in the assembly will need close
inspection.  They are fine, and even a little rust can be enough to wreck
them.

		Doug Jones
		jones at cs.uiowa.edu
______________________________________________________________
GreenKeys mailing list
Home: http://mailman.qth.net/mailman/listinfo/greenkeys
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:GreenKeys at mailman.qth.net

2002-to-present greenkeys archive:
http://mailman.qth.net/pipermail/greenkeys/
1998-to-2001 greenkeys archive:
http://mailman.qth.net/archive/greenkeys/greenkeys.html
Randy Guttery's 2001-to-2009 GreenKeys Search Tool:
http://comcents.com/tty/greenkeyssearch.html

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html Message
delivered to pj at pjbennett.com