Sparkly pixels

Discussions about Sinclair ZX80 and ZX81 Hardware
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: Sparkly pixels

Post by Lardo Boffin »

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.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
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PokeMon
Posts: 2264
Joined: Sat Sep 17, 2011 6:48 pm

Re: Sparkly pixels

Post by PokeMon »

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. 8-)

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 ?
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: Sparkly pixels

Post by Lardo Boffin »

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.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
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1024MAK
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Re: Sparkly pixels

Post by 1024MAK »

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
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Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: Sparkly pixels

Post by Lardo Boffin »

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.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
User avatar
PokeMon
Posts: 2264
Joined: Sat Sep 17, 2011 6:48 pm

Re: Sparkly pixels

Post by PokeMon »

Maybe good idea for a retro meeting and exchanging components between different users. :mrgreen:
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: Sparkly pixels

Post by Lardo Boffin »

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.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
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