Amiga 1200 AGA Screen Issues Vertical Lines

[BarneyBear]

Hi, I'm new here so please be kind.

I have owned this Amiga 1200 from new. When I got it out of storage everything seemed to work fine -once I had repaired the floppy drive.
The original hard drive still powered up and all was good except that the screen had thick vertical lines.
On the workbench screen there are 20 lines.
Just tried Turrican II AGA and there are 9 lines.

I have now sussed that these lines are only there when running in AGA or playing an AGA game. Normal older game play flawlessly.

The machine has been recapped and a flash drive put in to replace the original hard drive. There is an original A1200 8MB expansion from back in the 90's - battery still works! but the lines are there regardless of whether that is inserted or not.
The motherboard itself is very clean, doesn't get hot and hasn't been modified in any way.
The result is the same no matter what output or TV/monitor is used.

Anybody have any ideas?

[Boing-ball]

You might have board flex. Try pushing down on the Alice and Lisa chips whilst the computer is on (Try not to touch any pins). Then see if that changes the output for better.
If not Alice or Lisa, could be a Video DAC issue. Possibility of cold solder joints.

[BarneyBear]

Thank you.

I'll have a look at the weekend and feedback.

[BarneyBear]

I finally got round to looking at Alice and Lisa at the weekend and unfortunately it didn't make any difference.
I left the machine on for about 3 hours and again nothing got hot.

One thing that I did notice though, when using WHDLoad older games played without lines even though the machine booted with lines.
Clearly down to kick34005.A500 being executed.

AGA games though, still no go.