[comp.sys.dec.micro] Printing - LA50 XON/XOFF problems

heuer@decus.com.au (Powell HEUER) (12/21/89)

In article <847@tardis.Tymnet.COM>, jms@tardis.Tymnet.COM (Joe Smith) writes:
> The usual causes of this (XON/XOFF problems) are:
>   1) The computer is not configured to respond to XON/XOFF from the printer.
>   2) The cable to the printer is defective, and not passing pin 2 back.
>   3) The motherboard in the printer has gone defective and transmits garbage.
> 
> Case #3 is what I see a lot of.

I have encountered another cause of similar problems.
Unlike most other printers/terminals, it seems that pins 1 and 7 on the RS232
interface (protective and signal grounds) are not tied together at the LA50
chassis.  I found this out the hard way with a faulty cable that had a break in
one of these (I can't remember which).  The symptom was that the printer could
receive and print text but XON/XOFF characters it sent were not received
correctly.

This lack of correct ground could also make the printer more susceptible to
interference and damage to the logic board - a contribution to some of your
case #3's?