[GreenKeys] ASR-33 problem

Wed Jan 29 17:16:50 EST 2014

thanks for the pics... I just spent some time in exactly those areas
and lubed all the moving points I can find. Although I have not
removed the carriage assembly from the typing unit, it looks like a
scary job.

I've found the best way to try and reproduce the problem, although
it's still intermittent, is with a program on the PDP-8/A that prints
alternating characters and spaces.

It will print perfectly for five or ten lines, then start to print a
"-" or "*" instead of CR, LF and sometimes a space echoes as a tiny
"MA" (one character, it's just above space on the typewheel). Then it
will work normally for another five or ten lines without missing a
beat!

As Mike has pointed out, the problem is most likely in the print
suppression system. All I have been able to find so far is that the
codebar for print suppression (#9) feels like it's binding a little on
something when gently flexed from front to back. There is an
adjustable guide for the codebars in the middle of their span, but
tweaking that didn't help (although I could make it worse with
deliberate misadjustment).

Guess it's time to tear into it further!

I may have to remove the typing unit from the base to get a really
good look at the function levers and see exactly what's binding.

On Wed, 29 Jan 2014 14:21:49 -0500 (EST), you wrote:

>
>Charles,
>
>You are fighting the problem I always encounter when restoring a 33.  Congealed grease or dried up oil causing troubles.  
>
>One more question.  Is the 33 failing to return the carriage or perform a line feed when it fails or is it printing a character as it does the CR or LF?
>
>Either way its likely sticking levers in the carriage or function pawls depending on your answer.  I use "Breakaway" on parts that are stuck with congealed grease etc.  Use it very carefully and sparingly with the wand.  It doesnt smell good but the smell will go away in a few days.  Dont spray it on any KYBD, TR or AB plastic contact assemblys.  
>
>Try lubing the carriage area with good lightweight oil like 3 in 1 or the Breakaway.  Also lube the CR and LF function levers and pawls.  See attached pic for another area that almost always does some sticking when the 33 is not used for a long time.  Also a pic of the code bars.  You can see the function levers under.  
>
>The function levers are horizontal under the code bars running front to back.  The corresponding pawls are vertical in the white metal casting that runs along the rear of the carriage under the platen.    
>
>You might use the Breakaway on the code bars on each end and in the middle where they ride on shafts with grooves for each code bar.  More pics.  
>
>Wayne
>
>
>
>
>-----Original Message-----
>From: Charles <charlesmorris800 at centurytel.net>
>To: Teletypeparts <teletypeparts at aol.com>
>Sent: Tue, Jan 28, 2014 10:30 pm
>Subject: Re: [GreenKeys] ASR-33 problem
>
>
>well, if you prefer, 215 octal vs. 255 (which is what the old PDP
>omputers speak) 
>)
>Yes, the printer is really 7-bit ASCII since it obviously does not
>andle the extended 8-bit character set - it doesn't even have lower
>ase...
>The code bars are behaving normally, because the proper bits are
>lways being "punched" (I use quotes here since the punch may be
>urned off, but the ends of the bars at the left side of the typing
>nit can be seen/felt to be correct, and when punching tape it does
>ot have the false bit set).
>I think Mike is right that the problem is in the actuation of the
>unction bars. In fact, there seems to be some data sensitivity (i.e.
>hether or not the CR has the stuck bit 6 depends on the characters
>yped just before it) but I have not yet identified that pattern. Wish
> had a degreaser tank and could just dunk the whole typing unit (less
>he obvious pieces).
>-Charles
>s I go to central Maine for 1 week, only twice a year now. Haven't
>een to northern Maine in nearly a year and have no plans to go back
>ny time soon (admininstration and mid-managers don't see things my
>ay any more). I am fed up with "suits".
>
>n Tue, 28 Jan 2014 22:21:33 -0500 (EST), you wrote:
>>
>Charles,
>
>I dont speak hexidecimal very well.  
>
>Only the 33 kybd or your computer generates the 8th pulse.  Of course if its in 
>he punched tape the tape reader will read it.  
>
>The printer ignores the 8th pulse other than capturing it for the tape punch.  
>
>I wish I could think of what the trouble might be but nothing comes to mind 
>onight.  I will give it some thought.  You might look for a broken spring on 
>he code bars etc.  Most 33 problems are found visually.  
>
>BTW, are you still commuting between Missouri and Maine?
>
>Wayne
>
>
>
>
>-----Original Message-----
>From: Charles <charlesmorris800 at centurytel.net>
>To: Teletypeparts <teletypeparts at aol.com>
>Cc: deramp5113 <deramp5113 at yahoo.com>
>Sent: Tue, Jan 28, 2014 7:27 pm
>Subject: Re: [GreenKeys] ASR-33 problem
>
>
>yes, it behaves the same whether the PDP-8 is driving it, or local
>ode, or reading a punched tape with nothing but numbers and CR, LF...
>In fact, there is a pattern. Bit 8 is parity so I expect that one to
>hange based on the sum of the other 7... and:
>CR is x0001101 (0D hex)
>-   is x0101101 (2D hex)
>LF is x0001010 (0A hex)
>* is x0101010 (2A hex).
>http://www.ascii-code.com/
>So you can see the problem is that bit 6 is getting set sometimes,
>hen it shouldn't.
>-Charles
>
>n Tue, 28 Jan 2014 19:02:57 -0500 (EST), you wrote:
>>
>Charles,
>
>Does it work perfectly in Local mode?
>
>- is     1 3 4 6 marking
>CR is 1 3 4 8 marking
>
>* is     2 4 6 8 marking
>LF  is 2 4       marking
>
>I dont see any pattern there unless I am missing something.  Does the carriage 
>eturn properly and the line feed work correctly.  
>
>Wayne  
>
>
>
>
>-----Original Message-----
>From: Charles <charlesmorris800 at centurytel.net>
>To: greenkeys <greenkeys at mailman.qth.net>
>Sent: Tue, Jan 28, 2014 2:33 pm
>Subject: [GreenKeys] ASR-33 problem
>
>
>My ASR-33 has an interesting problem. Sometimes it does not "print" a
>arriage return, but echoes a dash ("-"). Same for a line feed which
>choes as "*".
>The tape punch, however, shows the correct code, so it's not a
>istributor problem. Punching a tape with repeated CR's, which I can
>ee has the proper code, also sometimes returns the carriage several
>imes in a row, but then will print a dash.
>So the problem is somewhere between the codebars and the typewheel,
>nd looks like a single bit sticking high (mark). Any hints?
>thanks
>harles
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