Editing Sinclair QL Troubleshooting Guide (section)

=== Symptoms and what they point to ===

{| class="wikitable styled-table" style="width:100%; text-align:left;"
! Symptom !! Likely cause !! Action
|-
| Picture appears and disappears when the lead is moved or wiggled || Cracked solder joints at J7, or a lifted pad || Reflow all eight pins; inspect pads under magnification; repair broken tracks with wire links
|-
| One colour permanently missing (e.g. no red) || Broken track or cracked joint on that pin — or that output of the ZX8301 has failed || Buzz out the pin from J7 back to the ZX8301; if continuity is good, suspect IC22
|-
| No RGB picture at all, but the machine clearly boots (TV output works, Microdrives run) || Sync or all-colour loss at the connector, or a failed ZX8301 video section || Check CSYNC and RGB at J7; renew IC22 if signals are absent at the chip
|-
| No colour on the monitor at all but a monochrome image is present || Loss of the RGB lines with sync intact || Check the RGB pins and their tracks
|-
| Machine died immediately after plugging or unplugging a monitor lead while powered || ZX8301 destroyed || Renew IC22 (socketed); fit protection before reconnecting
|-
| No colour monitor output (general) || Service Manual: renew IC22 || Substitute the ZX8301
|-
| Blurred picture; picture drifting; gradual colour loss in use || Service Manual: renew IC22 || Substitute the ZX8301
|}

Sources: Service Manual fault-finding guide and the video notes.<ref name="sm" /><ref name="junker" />