[GreenKeys] Re: busted 33ASR

[gil smith]

Hi Dave:

At 01:10 pm 8/8/03, you wrote:
>Gil--
>
>I rec'd the TTY, and she was smashed during shipping.

Ahh -- I hate to hear that.  So few of these left, and when a good home is 
found, the unit does not make it there safely.  I hope the damage to your 
unit can be repaired.


>I've got problems with the keyboard [the four little
>spring/rocker arms for the CTRL and SHIFT keys got
>tangled], the two solenoid sort-of rocker arms right
>above the answerback wheels were bent, one of the
>spindles for the ribbon is bent, the CCU was smashed
>up, and the plastic cover is basically shattered.
>
>She's generally responsive to keyboard input after I
>put that H-shaped thing rocker thing back between the
>keyboard and the rest of the works; most times the
>characters are wrong, and sometimes it repeats
>continuously until I hit another key.

Do you have any pics of the damaged areas?



>***I was wondering if it's possible to remove the
>keyboard and CCU and just drive the printer portion of
>things using a current loop [like a 33-RO?].  This
>way, I can get the printer back in order before
>dealing with fixing the damage to the keyboard, which
>is making it more difficult to isolate problems...
>
>Is it even possible to sidestep the CCU completely?

I believe the keyboard can simply be disconnected, but I have not tried it, 
and would have to find my manual to learn some more.

To completely eliminate the CCU would require that you properly drive the 
typing unit magnet (solenoid) with 500-mA or something like that.  There is 
a small board in the CCU, called the magnet-driver, that converts an 
internal 20-mA loop to the level needed to operate the magnets.

I also have a 33ASR with the TWX CCU.  Mine has a problem in the 
electronics, so I dug through the schematics and found a point on the CCU 
magnet-driver card where I could tap into the internal 20-mil loop to drive 
the typing unit (bypassing most of the electronics).  It has been a couple 
of years, and much of my stuff is still packed after a recent move, but 
I'll see if can dig some info out.  I may also have some of the repair 
parts you need.

Also, my mag-driver card had some power resistors that had de-soldered 
themselves from the circuit traces, due to heat not being dissipated 
well.  Take a good look at yours.


>I think I may have a current-loop to 232 adapter to
>drive the thing from a WYSE teminal and null-modem

If the wyse can be set for 110-baud, 8-bits, even parity, and 2-stop bits, 
it should work using your adapter and tapping into the mag-driver card, I 
believe.  I think it was only the early keyboards that generated even 
parity, and the later ones went to mark-parity.  I am not certain whether 
parity matters to the typing unit or not.  This is all off the top of my 
head at the moment.


>My other unit is a WU-branded 32ASR, and this one it a
>BellSystem-branded 33 TWX with a WU Acquisition Tag
>from 1971, and the references to the BellSystem
>removed or covered up.  What the heck is that *THING*
>in the base of the unit?  Does your WU-branded 33 have
>that thing, or only the BellSystem units?

I don't think that WU vs. Bell vs. Teletype branding matters other than 
cosmetics (and possibly included options).  TWX machines should have a 
big-honkin' dataset box (modem) in the stand.  Mine is a 101D, for which I 
cannot locate schematics -- and I think my problem lies in the modem, as it 
allows the machine to cycle open-loop.  The 101C was more common, I 
think.  Does yours have an ID plate?  Any pics of it?  There may also be a 
small module in the stand, which is the power supply for the tape 
reader.  In the later 3300-series machines, the reader supply was 
apparently built into the CCU.

The dataset (modem) provides the interface to the telephone line for the 
old fsk standard that was used up to 300-baud (used at 110-baud on the 
33).  The ccu adds provisions for dialing the number etc.  As I understand 
it, the 33 can be set to auto-answer mode, plugged into a telephone line 
(or spare pbx extension), and a standard computer/modem can dial into it 
(from a different line/extension) via a terminal emulator.  Have not gotten 
this far with my 33-twx though.


>Sorry for imposing on your time; I don't really have
>anyone to talk to about this...

Always happy to talk about old tty stuff.  You can also ask on greenkeys -- 
Jack Hart and others are a fountain of 33 knowledge -- I also copied 
greenkeys on this email.


>My girlfriend is wondering why I keep buying "broken
>typewriters".

Ahh, tell her there are much worse hobbies for a guy to have.


gil