🚀 go-pugleaf

I have also experienced the horizontal bars on my atari 800.
However, the common fix of putting capacitors across the power supply
didn't help my situation.
I also looked at the power system with a scope and could find nothing
unusual.
I even had another 800 open at the same time and compared the two systems.
Then i resorted to basics - see if anything feels unusually warm.
I found that one of my large filter capacitors (4700 UF i believe) was
much warmer than the other.
The capacitors on the other 800 i was using for comparison were cool.
I would have thought that a defect of this kind would reflect in high ripple
and/or low input voltage into the regulator but neither was the case.
At any rate, replacing the capacitor fixed the problem.
Good luck.