Need help with ASR33 tape reader - major frustration!

From: Charles <charlesmorris_at_direcway.com>
Date: Sun Apr 6 21:12:00 2003

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
Received on Sun Apr 06 2003 - 21:12:00 BST