Part working ULAs

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

Part working ULAs

Post by Lardo Boffin »

Having bought one or two zeddys over the years I have seen a few dead ULAs (but more dead Z80s) but also have seen a few that have only part failed.

Currently I have three of these. Danger ULAs as I call them! If I have a dodgy zeddy I can plug one of these in without fear of damaging a good ULA.

Dodgy list:

1) Won’t load from tape. Everything else seems to work ok.
2) Won’t detect keyboard input from the internal connectors. Everything else works fine (including my Memotech external keyboard!)
3) Screen goes garbled when pressing certain keys. Otherwise seems ok.

Anyone else have any part working ULAs?
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
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Part working ULAs

Post by Moggy »

I had the dead "keyboard-works-with-Memotech-only" situation, can't say anything about whether tape load/save worked as, thanks to spands various, I haven't used a tape in over ten years and binned all my tapes (sacrilege I know) but everything is available as P file these days so no worries.
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: Part working ULAs

Post by Lardo Boffin »

To be fair I’m not really using tapes either - Wespi or TZXDuino. :D
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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Flatulentia
Posts: 93
Joined: Sun May 14, 2023 3:58 pm
Location: Cambridgeshire, UK

Re: Part working ULAs

Post by Flatulentia »

I have an early ULA that only loads within an incredibly narrow range of accepted input signal voltage. It's randomly completely blind to 3V3 logic levels on the TAPE IN pin which I'm assured by another member here should work fine.

The plan was to build an internal signal conditioner for this one, but I've given up now as my design runs a dummy load perfectly but this ULA refuses to see it properly.

I'm guessing it's a duffer as my previous ZX81 with the same ULA revision seemed to load everything from almost anything. :?
ZX81 with ZiLOG Z84 CMOS Z80, 32KB battery-backed Toshiba 55257 SRAM with charge status LED, Wilf's "Why Wait?" mod and switch-mode 5V regulator. 50/60Hz mode switch, composite video output with Zigg's back porch mod and 1080p60 HDMI output.
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1024MAK
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Re: Part working ULAs

Post by 1024MAK »

Also having a ZXpand and a ZXpand+, many of my Zeddies have never experienced tape loading since they were acquired my me…

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