TTYs and hunting and readers (was - Re: Paper tape and Cards...

From: James Willing <>
Date: Wed Jan 13 15:54:25 1999

On Wed, 13 Jan 1999, Chuck McManis wrote:

> When I got the PDP-8/e I wanted to add a Teletype (ASR-33) for its console.
> This being the one true console for a PDP-8.

Well... Maybe a '35 in a REAL large configuration... B^}

> So I started looking around,
> then deeper, then deeper still. After going to many ham swaps, lots of the
> Silicon Valley surplus scene, and the Internet I determined that 1996 was
> the year of the great TTY purge. Literally dozens of people told me, "I
> junked n of them last year." (in 1997 of course).

Sad, isn't it? But never give up! Far too often you just have to turn
over one more rock!

> ... I then was contacted by a wonderful person in Utah
> who actually had a running one and I bought it from him.

See, what did I tell you!

> However, that one
> was not wired for current loop (it had some home brewed RS-232 converter on
> it) and it's reader is not functioning. (No idea why yet.)

OK. A bit of seriousness here. In most of the TTYs I've worked on
(fought with?) over the years, when a reader suddenly (more or less) goes
non-functional, it is usually because the clutch trip solenoid has gone
south. (the coil usually goes open)

Disclaimer for next steps - BEWARE moving mechanical parts and exposed
voltage sources within the device that are unshielded when the cover is

If you are not familiar with safety procedures for working in this
environment, or are uncomfortable doing such things... STOP and find
someone who is!

Easiest way to tell for sure is to pull the top cover off, put a tape in
the reader, and move the control lever to the 'run' position. Based on
your description, nothing will happen...

Locate the reader transmission clutch solenoid (rear of the machine,
slightly in from the right side, above the main shaft), and the lever that
is latched by the solenoid. Manually trip the solenoid. (briefly, don't
hold it down)

If the clutch cycles with a loud clunk, accompanied by the reader
executing one read cycle and advancing the tape, (and possibly the unit
printing the tape character that was read) congradulations. You have
found the problem! Now, you just need to decide how to fix/replace the
coil. (too long a procedure to go into here)

> I say "at the moment" because I cannot tell if this lull is permanent or
> temporary. Lots of machine shops had ASR-33's and they might be converting
> them at some point. Jim Willing was looking for one too, I don't know if he
> found one or not. I know of two others, but how they will go is unknowable
> to me.

As with many things like this, its either flood or famine. I found one
after much struggle, and then ended up with multiples! And then, an
ASR-38 popped up! Again, it just took finding the right rock to look
under... Now I'm seeking the more elusive ASR-35 or 37!

And before anyone starts drooling, yes I am open for trades... Just what
I don't know yet. I still could use a MITS 'turnkey' card for an 8800B
turnkey unit... or a 'straight-8'! B^}

(hey... I can dream!)

The Computer Garage -
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Received on Wed Jan 13 1999 - 15:54:25 GMT

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