Quoted from creepykenny:your two garbled screen shots appear to both be monitor problems - as you mentioned loss of sync and output to the monitor may be ok ?
if possible hook up a different monitor to rule the original out
bad caps in monitor can cause quite a few issues over time
Ditto on the monitor problem. In my particular case it was the connector on the monitor chassis which comes from the VGA. The horizontal sync was intermittent and could be made to come and go by wiggling it. Took the monitor completely apart and found lots of cracked connections needing reflow on the monitor chassis. Been solid ever since.
Bethlehem, PA
