wtm@uhura.neoucom.EDU (Bill Mayhew) (10/07/90)
Thanks to Gary for re-posting the article I wrote about 3b1 monitor switches. I should add a couple of things. There are several defferent monitor types on 3b1/7300s, as I subsequently discovered. My personal 3b1 happened to be easy to usurp the power because it happened to have a glass mini fuse in a clip holder. Several moniorts I've seen since then don't have a clip-in fuse; they have soldered-in microfuses. The pin-outs for the video connector are on sheet 8 of the Rev J schematics, with functions as follows: JV-1 Video V Sync JV-2 GND JV-3 Video H Sync JV-4 GND JV-5 Video Out JV-6 GND JV-7 +12 VDC Power JV-8 GND JV-9 +12 VDC Power JV-10 GND JV-11 8 ohm speaker, lead 1 (see sheet 26) JV-12 8 ohm speaker, lead 2 The video clock rate is 20 MHz. The screen oganization is 720 bits wide x 348 bits tall. The screen is scanned non-interlaced starting at top left. H Sync and retrace is 11 word times (16 * 11 * 50 nS) = 8.8 uS V Sync and retrace is 1079 word times ( 863 uS) The video field rate is 60 fields/sec. The Unix PC video system is discussed on pages 2-78 through 2-86 of the Unix PC Technical Reference Manual. Remember, if you decide to work on your minotr that you need to follow proper electrical safety and tube implosion avoidance procedures. Untrained persons should not atttempt modifications or repairs. Hope this info helps, ==Bill== -- Bill Mayhew NEOUCOM Computer Services Department Rootstown, OH 44272-9995 USA phone: 216-325-2511 wtm@uhura.neoucom.edu ....!uunet!aablue!neoucom!wtm via internet: (140.220.001.001)