[GreenKeys] ASR33 tape reader

Wed, 9 Apr 2003 15:48:29 -0500

First make sure the shipping bolt is removed from the bottom of the base "pan"

Bouncing contacts cause all kinds of trouble with 33 readers.  The 
answerback drum in the rear of the machine and the keyboard contacts, 
controlled my the H lever, are both in parallel with the reader 
contacts.

Get out the adjustment manual and check the adjustment of the reader 
feed pawl.  If you need a M33 manual you can get one from Tom 
Kleinschmidt at <[email protected]>

Lots of patience is required when working on M33 ASRs.

Don

>
>>From: Charles <[email protected]>
>>To: [email protected]
>>Subject: Need help with ASR33 tape reader - major frustration!
>>Date: Sun, 06 Apr 2003 21:09:30 -0500
>>Reply-To: [email protected]
>>
>>I can't get my ASR33's tape reader to stop missing occasional
>>characters! I have lubed it and tried setting it according to the
>>procedures in the manual but that is very frustrating since many
>>of the adjustments interact.
>>
>>Using a test tape punched on the same TTY with 72 printable
>>characters per line (incrementing from space through Z and
>>punctuation, then LF + CR at end of each line), if I carefully
>>adjust the detent position I can achieve one (and occasionally 3
>>or 4 in a row) "skipped" characters about every 10-20 lines which
>>is roughly once every 1000 characters on average.
>>
>>I can load short tapes like the BIN loader and then the second
>>short section of 4K FOCAL successfully, but the long first section
>>of FOCAL (which takes over 10 mins. to read in) invariably gives a
>>checksum error. In other words, not good enough.
>>
>>The missing characters are not being read into the data stream at
>>all, nor are the previous or next characters duplicated. I wrote a
>>program to just read the characters into the AC and halt if a NUL
>>(000) is read. All 0's are indeed being read on the missed
>>character and I think this is because the contact pins are all
>>held down if there is a "misfeed" where the tape moves just enough
>>to put the pins between rows of holes, but not far enough to skip
>>to the next.
>>
>>Anyone with experience "tuning" this beast, please give me a hint!
>>thanks
>>Charles
>
>
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