Apple Performa 6400/180 - Manual (Page 79)

Troubleshooting Symptom Charts/Video - 5
Video
No video, fan is
running
1 Check monitor connection.
2 Try known-good monitor.
3 Replace monitor-out card.
4 Remove all DRAM DIMMs and try replacing them one at a time
to test. Replace any bad DIMMs.
5 Replace logic board. Retain customer’s DIMMs.
6 Replace power supply.
Blurry image over
entire screen at
resolutions of
832 x 624 and
higher.
Power Macintosh 6500 serial number falls within the range from
XB708xxxxx to XB723xxxxx, replace audio/monitor connection
subassembly (P/N 922-2996). To identify audio/monitor
connection subassembly that needs replacing, see Additional
Procedures chapter.