Annoying A1200 screen flicker / wavy on disk access

[F0LLETT]

From memory D215A. Is there a component there?
Fix is normally, ceramic cap across collector and emitter pads.

[F0LLETT]

Yeah... I recapped it long ago... It only happens on disk access so I'm certain its not the monitor.  I noticed its much worse with DF1 disk access than DF0.  It's clearly something to do with noise on the power rail but I still haven't found the source.  It's possible both drives need to be recapped. I may try recapping DF1 to see if it has any effect.

Is D215 populated?
If not, add a ceramic cap or ferrite across the bottom pads.

[F0LLETT]

I previously installed a new 1uF cap across 215A which is unpopulated.  No improvement.

What about C215 and R215. If you have them both populated, try removing R215. If its still same, try putting it back and removing C215. If not, then put it back on.
Just when had this issue in past, either D215A, R215 or 215 solved it.