Subject: Trouble with ASR33

From: Vintage Computer Festival <[email-masked]>
Date: Sat Mar 15 17:55:01 2003

I'm currently fighting with an ASR33 trying to make it perform a carriage
return.  Currently, the carriage is stuck all the way on the right side
and refuses to budge.  I tried to find something inside that would release
it but I haven't located the magic tab.

I've noticed something else.  When I have the punch turned on, the '8' bit
doesn't punch.  For instance, if I hit "RETURN" I get the 1 + 4 + 128 bits
punched, but no 8 (1 + 4 + 8 = 13).

I don't see anything obvious, like a level that's come loose for example.
I also lost the tab that holds the little plastic cover down over the
reader mechanism.  In trying to take the main cover off so I could look
inside, I didn't notice the two screws on the front until after much
wrangling, and just after the tab broke off and either fell or flew into
oblivion.

Whoever designed the ASR33 must have sold their soul to the devil to make
it all work.  It's amazing how intricate and delicate everything is, and
how damn kludgy as well.

I'm impressed, but not.

-- 

Sellam Ismail                                        Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger                http://www.vintage.org

 * Old computing resources for business and academia at www.VintageTech.com *

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From: Eric Chomko <[email-masked]>
Date: Sat Mar 15 19:11:00 2003

I'm looking for a color image of an Interdata 7/16 minicomputer.
Spies minicomputer orphanage has an nice B/W of the front panel,
I'm looking for a nice color image.

Thanks,
Eric

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From: Eric Chomko <[email-masked]>
Date: Sat Mar 15 19:22:00 2003

Look what I found on the net!

http://www.newbegin.com/itemmis_9.html

Not really what I had in mind, but...

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From: "Jonathan Engdahl" <[email-masked]>
Date: Sat Mar 15 20:06:01 2003

I know that front panel Oh so well. My second computer job was programming a
7/32. I have a 7/16 front panel I bought off eBay for sentimental reasons.
It's almost the same except it has single LEDs populated instead of 7
segment LEDs. I can take a picture of it for you, but it's pretty banged up.

I have a manual containing the schematics and microcode for the 7/32. Al
Kossow scanned it and it's on his site.
http://www.spies.com/~aek/pdf/interdata/29-535_7-32C_Maint.pdf

--
Jonathan Engdahl
http://users.safeaccess.com/engdahl

"The things which are seen are temporary,
 but the things which are not seen are eternal."  II Cor. 4:18

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From: [email-masked] (Tony Duell)
Date: Sun Mar 16 13:31:00 2003

> punched, but no 8 (1 + 4 + 8 = 13).

The 2 problems could be related. The 'block level description' of the 
machine is : 

Incoming data goes to the solenoid on the RX mechanism (rear left of the 
'typing unit' (main chassis)). 

The RX mechanism samples the position of the solenoid armature (there's a 
camshaft in the middle of said unit), and thus converts the data to parallel.

The parallel data goes onto the rails that run across the machine under 
the carriage (one rail for each bit).

3 mechanisms use these rails : 
 a) The carriage, which decodes printing characters and prints them
 b) The punch, mechanically coupled to the left end of the rails
 c) The function unit ('Stunt box') which decodes control characters and 
    performs the appropriate function.

So if the return character is not getting to the rails correctly then 
firstly it won't punch properly and secondly, it won't be detected by the 
approipriate lever in the function unit.

So let's get that missing bit back first. Are you running the machine in 
LOCAL mode (i.e. from its own keyboard to the printer?). If so, the 
problem could be in the transmitter side (contacts on the keyboard, for 
example). Or it could be a problem in the RX unit (sticking lever). I 
think it's safe to assume that the solenoid driver is not the problem 
here (it's not going to mangle only one bit).

Incidentally, the carriage is fed by the 'spacing mechanism' which drives 
the left hand sprocket for the toothed belt. At the bottom of this 
sprocket shaft, right against the casing, is the spacing ratchet with the 
pawls to move it on one character, and to allow it to be released for a 
carriage return. IIRC, _carefully_ frobbing levers in this area will 
release the pawls and allow the carriage to return.

> it all work.  It's amazing how intricate and delicate everything is, and

I find them rather beautiful...

-tony

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From: Eric Chomko <[email-masked]>
Date: Sun Mar 16 14:28:00 2003

This has me thinking that I should drag mine out and test it. Being the
new millennium and all...

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From: [email-masked] (Tony Duell)
Date: Sun Mar 16 17:19:00 2003

> new millennium and all...

I can assure you that the ASR33 does not suffer from any Y2K bug :-)

-tony

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From: Eric Chomko <[email-masked]>
Date: Sun Mar 16 22:19:01 2003

> I can assure you that the ASR33 does not suffer from any Y2K bug :-)

You haven't seen where I store it!

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From: Vintage Computer Festival <[email-masked]>
Date: Mon Mar 17 11:04:00 2003

> approipriate lever in the function unit.

I haven't be able to verify what character is being produced because the
durn carriage is stuck on the right.  Once I get the carriage returned
then I can determine what's going on.

> LOCAL mode (i.e. from its own keyboard to the printer?). If so, the

Yes, LOCAL mode.

> here (it's not going to mangle only one bit).

While I can't say I examined it to the point of ruling this out, I didn't
notice anything wrong with the levers.  However, it is an obvious place to
start.

> release the pawls and allow the carriage to return.

I'll look into that.  This is my primary concern as of now.

> I find them rather beautiful...

I agree, but I still can't believe this thing works and stays together as
it does considering how delicate all the parts are and how delicately
everything hangs in balance.

--

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From: [email-masked] (Tony Duell)
Date: Mon Mar 17 18:36:57 2003

> then I can determine what's going on.

Sure you can. In fact the carriage won't help you much anyway because it 
onlly really decodes printing characters. 

Look at the selector rails. You'll see there are 8 of them (at least 
where they connect to the punch), and it's not hard, even without the 
manual, to work out which state is a 0 and which is a 1, and what the bit 
sequence is. Then you can see how they're set for each character.

Another trick is to use the reader. Open the cover (trivial for you), 
hold down the tape sensor, and turn it on. Then hold down various 
combinations of the pecker pins and see what happens. If you can get a 
friend to help,, you could probably hold down the right combination for a 
CR -- and see if the carriage then returns. If it does, then you've got a 
keyboard problem, of course.

> notice anything wrong with the levers.  However, it is an obvious place to

Actually, since you're working in local mode, I'd start with the keyboard 
and distributor contacts. The former, particularly, are known to give 
problems in old machines.

-tony