Discussions about Sinclair ZX80 and ZX81 Hardware
1024MAK
Posts: 5162 Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...
Post
by 1024MAK » Tue Aug 01, 2023 11:35 pm
Lardo Boffin wrote: ↑ Tue Aug 01, 2023 11:07 pm
I moved the ULA to another zeddy and the hold issue didn’t move with it so I guess I should be ok to refurb this one.
Did you try a different ULA in the suspect board?
Mark
Lardo Boffin
Posts: 2185 Joined: Sat Nov 26, 2016 2:42 am
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by Lardo Boffin » Wed Aug 02, 2023 12:44 am
No but I will do so thanks.
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
Lardo Boffin
Posts: 2185 Joined: Sat Nov 26, 2016 2:42 am
Post
by Lardo Boffin » Thu Sep 07, 2023 11:41 pm
I finally tried a different ULA in this one and got exactly the same issues. I guess the issue is in or related to the modulator?
Regardless I fitted a ZX8-CCB and it now gives a perfect picture.
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
1024MAK
Posts: 5162 Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...
Post
by 1024MAK » Fri Sep 08, 2023 12:50 am
Ahh, the good old tried and trusted process of elimination
Obviously, it’s always the last thing
Mark
Lardo Boffin
Posts: 2185 Joined: Sat Nov 26, 2016 2:42 am
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by Lardo Boffin » Sat Sep 09, 2023 12:13 am
Lacking skill and suitable equipment elimination is my friend!
Having connected up the ZX8-CCB the picture is the same as my Timex 1000. Interesting.
Normally the K is further up the screen and the top row further down the screen.
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
1024MAK
Posts: 5162 Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...
Post
by 1024MAK » Sat Sep 09, 2023 10:48 am
Now, if you had an item of test equipment that could measure frequency, I would be suggesting you test pin 6 on the Z80 to see exactly what frequency it’s running at
I presume you have checked R30 / ULA pin 22?
Mark
Lardo Boffin
Posts: 2185 Joined: Sat Nov 26, 2016 2:42 am
Post
by Lardo Boffin » Sat Sep 09, 2023 12:20 pm
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
Exile
Posts: 48 Joined: Tue Jan 03, 2023 9:50 pm
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by Exile » Sat Sep 09, 2023 1:39 pm
I suspect most of the people buying my zeddies play 3D monster maze a few times and then don’t switch it on again
I'm still using mine regularly, but then I've never played 3D monster maze on it
Looks like I have R30.
I guess that goes with "USA1" being written on the silk screen between the modulator and the ULA
Lardo Boffin
Posts: 2185 Joined: Sat Nov 26, 2016 2:42 am
Post
by Lardo Boffin » Sat Sep 09, 2023 3:54 pm
Excellent on the still being used front!
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
redgatemodels
Posts: 172 Joined: Tue Sep 05, 2023 11:56 am
Post
by redgatemodels » Fri Sep 15, 2023 1:58 pm
Exile wrote: ↑ Sat Sep 09, 2023 1:39 pm
I'm still using mine regularly, but then I've never played 3D monster maze on it
Wasn't that the point of a ZX81