[GreenKeys] [External] Re: 33 ASR Troubleshooting - keyboard works in local mode but not line, etc.

[Jones, Douglas W]

Thomas Moss needs to check to see if his 33 ASR machines contain the DEC modification.  This modification uses a third pair of wires (pair 1 is receive data, pair 2 is transmit data) to allow for flow control when reading from paper tape.  This involves a reed relay to interrupt the power to the tape-reader's solenoid when the computer isn't willing to receive data.

The reader-run relay mounts on the vertical bracket on the left side of the UCC framework.  See this photo, taken with the reader-run power supply removed:
-- https://homepage.divms.uiowa.edu/~jones/pdp8/UI-8/2014/04/25-TTYreaderRun.JPG

If this is installed, your will not read tape when it's on-line unless a cooperating computer tells it to.

Here's the list of all the things we've fixed on the U of Iowa's 33 ASR:
-- https://homepage.divms.uiowa.edu/~jones/pdp8/UI-8/bugs.shtml#TTY33