[GreenKeys] ASR-33 problem

[Mike Douglas]

Your problem had nothing to do with ASCII encoding, the parity bit, etc.  Again, based on your observation that a received (or local) CR or LF always punches a CR or LF, then your selector, blocking bars and codebars (and keyboard if done in local mode) are all working correctly. This further implies that a range adjustment is not in order.

If you look at the codebar to typewheel linkage (note that only codebars 1-5 and 7 are used), you'll see that a CR and the "-" both move the typewheel to print the "-" character.  The only difference is that when a CR is received, the CR function bar raises and blocks the print suppression bar, and therefore prevents the "-" from printing. If the print suppression bar is not blocked, then a CR will print a "-". The same is true of a LF and a '*'.

Your problem is that the CR and LF function bars are not rising fully every time which causes two problems, 1) the print suppress bar is not blocked and therefore the '-' or '*' prints, and 2) because the function bar does not always rise fully, the CR or LF function pawl does not engage and therefore the CR or LF function does not activate on those occasions.

Mike


> On Jan 28, 2014, at 6:19 PM, Charles <charlesmorris800 at centurytel.net> wrote:
> 
> yes, it behaves the same whether the PDP-8 is driving it, or local
> mode, 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
> change 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,
> when it shouldn't.
> 
> -Charles
> 
> 
>> On 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 return 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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