Weird fault on Harlequin 128k ZX Spectrum...Help!

[Hagonator73]

Hello,
I have just finished building a Harlequin 128k ZX Spectrum superflo......This is not the first one I have done, However, on completion of this one, something unusual is happening I haven't seen before.
Upon powering up the Harlequin Board boots up into the home screen but there is flickering and some pixel gaps in the title screen. I'll put some pictures up

As you can see from the pictures it kinda works, but dosent.
I rechecked all solder points to rule out any bridging or bad solder joints. - All solder joints appear fine.
I readjusted and rechecked all chip and chip Placements- All appears fine.
Re- soldered the 2 crystals and the barrel jack and checked all caps and resister points.
- all seems fine
I checked all polarity of caps- all seems fine
I swapped the CPU. same problem??
I'm sure it's something quite straight forward that I'm missing bit I just can't see it.
Please, if there is anyone that's seen this before or who can help/assist please let me know, I've spent too many evenings trying to figure it out and its driving me nuts. Thank you
Andy

[redgatemodels]

Is this Composite or S-video?

I get some horrible glitching on one TV only when using S-Video, I have assumed it's the TV.

[Hagonator73]

Hello,
It is a composite connection, However, I have an identical Harlequin board I put together and the picture on the same TV is perfect same connection, So, I have ruled out the TV

[1024MAK]

Not had a chance to watch the video yet.

If the problem is random short white lines across the whole screen on the video picture but without any corruption of the RAM contents, it could be that the contention circuitry is not pausing the Z80A processor.

The Z80A processor has to be paused so that the circuitry that gets the video data from RAM can do this without being overridden by the processor.

Mark

[Hagonator73]

Hello Mark,
I hope you get to see the video, its like a flickering slight image distortion and gaps I the home screen. I did change the CPU with a spare I had but this has had no change to the image. Its immensely frustrating