Sinclair ZX80 / ZX81 / Z88 Forums

siggi wrote: ↑Tue Apr 04, 2017 10:18 am Is the +5V power OK? Or is there a lot of "noise" or peaks or voltage drops? Maybe you have to replace old capacitors (if not already done) ...

Regards
Siggi

Not sure about the power but I imagine that they would have checked such things.

The capacitors have been changed while they had it (as well as the ULA being heat sinked - don't tell Moggy!!) but that didn't fix the issue.

Well - take it sporty. Nobody else has this type of machine. What ever caused the effect, you have an unique machine, that's what counts.

I don't think that this is a timing issue. If data would be read wrong there should be distortions char wide (8 pixels following each other) at least partly. Here is just one single pixel down. I would say this could be an ULA issue even if it does not occur without ZXpand. Did you ever try another ULA ?

PokeMon wrote: ↑Tue Apr 04, 2017 1:45 pm Did you ever try another ULA ?

I tried one and I think MCG who fixed it tried some different ones as well. It was changing the ROM that seems to have finally fixed it.

I'm not sure the numbers of ZXpand and ZX81 are as you suggest.
Some ZXpands are being used with ZX80 computers.
And in my case, the ZX81 ZXpands that I have normally stay attached to the same ZX81 machines. So it is possible that some of mine may have similar symptoms but I would not know.

Mark

1024MAK wrote: ↑Tue Apr 04, 2017 2:55 pm I'm not sure the numbers of ZXpand and ZX81 are as you suggest.
Some ZXpands are being used with ZX80 computers.
And in my case, the ZX81 ZXpands that I have normally stay attached to the same ZX81 machines. So it is possible that some of mine may have similar symptoms but I would not know.

Mark

Fair comment - I was potentially exaggerating a bit to emphasise the fact that in reality not many zeddys have been near a ZXPand as a percentage of how many there are.

Maybe good idea for a retro meeting and exchanging components between different users.

I have just had another sparkly pixel zeddy. This time with a vULA81 fitted.

The cure was to change the ROM. Sadly I am now out of spare ROMs.