Hi, been a while since I posted and as usual, I need some advice
I am trying to bring a ZX81 rev. 3 back to life. I have socketed all ICs and replaced the transistors. I'm using Andy Rea's ULA81 (I believe its the version 1 as it doesn't have the Altera chip and only has one jumper on top of the board). I'm also using the 32K memory board from http://speccy.pl/wiki/index.php?title=ZX81_32K
I have a 3.24Mhz frequency on Z80/pin 6 and a nice back-porch signal at the ULA and modulator via. This gives a steady white screen on the monitor but no cursor.
The video signal is 2V, has the back porch but no character info. I have connected the via for the signal directly to the video cinch.
Can someone point me to any fitting/configuration instructions for this ULA81?
And is the signal composite compatible directly from the ULA or do I need to use something like Pokemons CCB board?
Dave
Andy Rea's ULA81 Mk1
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Re: Andy Rea's ULA81 Mk1
I have this manual I downloaded for one of these a while back.
- Attachments
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- zxula doc v2.pdf
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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
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
Re: Andy Rea's ULA81 Mk1
Perfect, thanks.
I'll have a cuppa and a read.
Dave
I'll have a cuppa and a read.
Dave