[GreenKeys] ASR-33 problem
Teletypeparts
teletypeparts at aol.com
Thu Jan 30 15:43:37 EST 2014
Dang Charles,
Well done!
Wayne
-----Original Message-----
From: Charles <charlesmorris800 at centurytel.net>
To: Mike Douglas <deramp5113 at yahoo.com>
Cc: Teletypeparts <teletypeparts at aol.com>; greenkeys <greenkeys at mailman.qth.net>
Sent: Thu, Jan 30, 2014 3:40 pm
Subject: Re: [GreenKeys] ASR-33 problem
I think it's finally fixed (along with all the other stuff I broke
essing around with it)... a slight adjustment of the "PRINT
UPPRESSION LATCH - HORIZONTAL CLEARANCE" and the seems to have cured
he binding, along with plenty of light oil to every sliding point
ithin view...
Having removed the typing unit to fix the line feed latch spring that
ame off, and make a replacement "lobe plate" which broke off from
eturning the carriage without the dashpot, (just like the manual
arns), then I found the keyboard had a bit stuck high. It turned out
he shorted bit was actually on the answerback drum contact :P
THEN I noticed that another bit was stuck in space... so the effect
as of holding the shift key down when it wasn't. That wasn't quite as
ard to find, just a wire on the right side of the keyboard on the
hift T-levers needed a little adjustment with needlenose.
Finally I printed about a foot of paper, margin to margin (the
irectory of my PDP-8/A's operating system pack, in case anyone cares)
o extraneous characters or failure to CR or LF either :)
That's it, I'm putting the covers back on. If it ain't fixed it's
lose enough!!
On Thu, 30 Jan 2014 09:01:29 -0600, you wrote:
>Charles,
The print suppression mechanism doesn't sound like it's a problem, instead, it
s a symptom of the problem. Because the CR function bar (for example) doesn't
ise fully, the print suppression mechanism fails to suppress the print head so
-" prints. Also, the CR function pawl fails to engage and so the CR function
oes not occur either.
Mike
On Jan 29, 2014, at 4:16 PM, Charles <charlesmorris800 at centurytel.net> wrote:
> 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.
ongealed grease or dried up oil causing troubles.
>>
>> One more question. Is the 33 failing to return the carriage or perform a
ine 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
epending on your answer. I use "Breakaway" on parts that are stuck with
ongealed grease etc. Use it very carefully and sparingly with the wand. It
oesnt smell good but the smell will go away in a few days. Dont spray it on
ny KYBD, TR or AB plastic contact assemblys.
>>
>> Try lubing the carriage area with good lightweight oil like 3 in 1 or the
reakaway. Also lube the CR and LF function levers and pawls. See attached pic
or another area that almost always does some sticking when the 33 is not used
or a long time. Also a pic of the code bars. You can see the function levers
nder.
>>
>> The function levers are horizontal under the code bars running front to
ack. The corresponding pawls are vertical in the white metal casting that runs
long the rear of the carriage under the platen.
>>
>> You might use the Breakaway on the code bars on each end and in the middle
here 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
n
>> he punched tape the tape reader will read it.
>>
>> The printer ignores the 8th pulse other than capturing it for the tape
unch.
>>
>> 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
arriage
>> 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
>> ______________________________________________________________
>> reenKeys mailing list
>> ome: http://mailman.qth.net/mailman/listinfo/greenkeys
>> elp: http://mailman.qth.net/mmfaq.htm
>> ost: mailto:GreenKeys at mailman.qth.net
>> 2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
>> 998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
>> andy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html
>> This list hosted by: http://www.qsl.net
>> lease help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20140130/5f5809c9/attachment.html>
More information about the GreenKeys
mailing list