8-bit acorn hardware • CUB Monitor 1431-MS: Stable Wavy Horizontal Display

I have a CUB Monitor 1431-MS (blue PCB - LCCD03 [3]) with a good bright picture, but a stable wave effect, most noticable along the horizontal sides as pictured. I'd love to get that sorted for some photos I want to use the screen for. Any help would be appreciated.
https://www.dropbox.com/scl/fi/79pakvva ... xtero&dl=0

But for when there's something to display that's not filling the edges with colour, vertical lines look perfectly fine to my eyes:

https://www.dropbox.com/scl/fi/kbw6rlhk ... nhevc&dl=0
I could dial in the pots slightly better to get a more consistant size of text by the way. All the pots work. Nothing cures the wonk.

I've replaced the Tripler (that solved the progressive blurring and sparkles) and lots of the capacitors (see below) which seemd to give a bit more control from some of the pots, which I De-oxited, cleaned and tested.

My feeling is that there's an issue around the VR321 area. I cleaned the pot which out of circuit seems in spec, but in circuit in effect, only gives me two stable settings: bowed in edges, or warped outwards edges as pictured. I'm no genius with this stuff, and don't have an oscilloscope. Just wondered if anyone knows what might be the next step (including give up, send to an expert, and so on).

All replaced:
C11 – 100uF 400V (radial)
C12 – 4.7uF 35V (radial) - 4.7uf - 63V
C23 – 4.7uF 35V (radial) 4.7uf - 63V
C26 – 10uF 350V (radial)
C27 – 47uF 250V 105C (radial)
C28 – 47uF 250V 105C (radial)
C31 – 470 uF 25V (radial)
C34 – 220uF 25V (radial)
C101 – 10uF 35V (radial)
C102 – 10uF 35V (radial)
C105 – 10uF 35V (radial)
C206 – 0.68uF/680nf 50V (axial) - 0.68uF 63V
C207 – 4.7uF 35V (radial) - 4.7uF 67V
C212 – 220uF 25V (radial)
C224 – 1000uF 40V (radial)
C304 – 100uF 35V (radial)
C308 – 10uF 35V (radial)
C311 – 470uF 35V (radial)
C312 – 220uF 25V (radial)

Statistics: Posted by OneSwitch — Wed Oct 01, 2025 9:13 pm

---