Posted By
JamesC
on 2015-11-27
13:22:05
|  Re: Plus4 video problems
You're losing your 5V somewhere in the system. (C7 staying at 10V means we don't have to worry about the 9V side.)
Two publications to assist you in diagnosing:
1. Sam's Compufacts has the wiring diagram, with expected volatages on each pin of the major ICs.
http://plus4world.powweb.com/publications/SAMS_Computerfacts_CC9_Commodore_Plus4
2. Commodore issued a technical advisory for trouble-prone things. Refer to pages 1 and 2.
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/plus4-troubleshooting-1of4.gif
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/plus4-troubleshooting-2of4.gif
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/plus4-troubleshooting-3of4.gif
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/plus4-troubleshooting-4of4.gif
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