[vcf-midatlantic] DIP switches

Mike Loewen mloewen at cpumagic.scol.pa.us
Wed Mar 27 23:12:16 EDT 2019

    Don't neglect them while troubleshooting, especially the little red 
bastards.  :-)  My HP 2647A graphics terminal developed what appeared to be a 
sync problem when displaying more than one line of text.  Swapping the suspect 
cards with known good ones from another terminal didn't change a thing.  All 
self-tests passed, including text RAM and graphics RAM.  Graphics mode worked 
perfectly.  I finally swapped the two RAM cards (32K on each), changing the 
DIP switch configurations on each.  At last, a RAM error.  I excercised all of 
the DIP switches, put everything back together and it worked.

    This is the second time I've had problems with DIP switches in vintage HP 
gear.  The other was in a 2117F I was working on for Dave McGuire.  Same cure.

Mike Loewen				mloewen at cpumagic.scol.pa.us
Old Technology				http://q7.neurotica.com/Oldtech/

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