ocr: PLUS 4 Troubleshooting Page 2 2) BAD VIDEO - Scrolling lines on screen - Random blocks on screen - Blurred display A) Check J1-J6 for shorts to ground or each other 0.K. * B) Check reset for correct operation 0.K. * C) Check Ul for proper operation 0.K. If not: 1) Check socket for good solder * 2) Check for bad Ul D) Check U2 for proper operation 0.K. If not: 1) Check socket * 2) Check for bad U2 E) Check RAM data lines for correct amplitude 0.K. If not: 1) Check for hot surface of RAM * 2) Jump out RAM to verify F) Check multiplexers U9, U10 - signals at RP3 and RP4 should be similar in frequ ...
