Old TV as a ZX80 monitor may not be optimum

Discussions about Sinclair ZX80 and ZX81 Hardware
Moggy
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Moggy »

Yup that does indeed seem to be the wee beasty! :D
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1024MAK
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Re: Old TV as a ZX80 monitor may not be optimum

Post by 1024MAK »

Creator wrote: Thu Jul 28, 2022 4:00 pm Looks like the same product. https://www.ebay.com/itm/174949505611
Yeah, that’s fine. zebranyc (Zebra Systems) has been selling Timex/Sinclair bits for some time.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

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There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
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1024MAK
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Re: Old TV as a ZX80 monitor may not be optimum

Post by 1024MAK »

Moggy wrote: Thu Jul 28, 2022 3:37 pm A note of caution re the ebay video boards especially the ones that have a 555 chip installed. I do believe that some people have had problems with these devices.
The topic where I looked at one version of the video boards based on a NE555 is here. But note that there may well be a number of different versions from different sellers.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
Lardo Boffin
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Lardo Boffin »

Just another voice in support of Pokemon. Or picture…

These arrived today. I think this makes either 55 or 60 of these I will have fitted. The keyboards are excellent as well!

B49834A2-BDA6-4886-B442-DDD0195E4B00.jpeg
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
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Lardo Boffin »

Creator wrote: Thu Jul 28, 2022 3:27 pm
Laedo Boffin
My SDcard project (Xiao, Op Amp, software) is kinda interesting but has its limits, really just a 'can I make this work' kinda thing. It uses existing Load & Save commands so really no speed increase. On Save it monitors the data stream storing all valid pulses then when complete parses and converts to 1's & 0's which are saved to SDcard file so savable ZX80 program size is limited by available memory (currently 32k Xiao). An improvement would be to monitor / parse on the fly but that presents some issues I haven't tackled yet but may in the future. Load is just reading the SDcard file and generating proper pulse patterns for the stored 1's & 0's.
Sounds pretty good to me! I have used TZXDuinos which don’t load any faster than tape in the past. They also don’t allow you to save files. So this would be a big improvement.
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
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Moggy »

By curious happenstance I've just ordered one of those clicky keyboards, hope they are worth their salt unlike the dreadful ZX80 membrane replacement I wish I hadn't bothered with, granite keys would be kinder to the old digits than that horror :lol: .
Creator
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Creator »

OK, ordered the video card, gotta be an improvement. Eyeballing the keyboards ! Went looking for some books on machine language for the ZX80 & ROM deciphering. Haven't done much of either of those since my TRS-80 days, could be fun.
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mrtinb
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Re: Old TV as a ZX80 monitor may not be optimum

Post by mrtinb »

Creator wrote: Thu Jul 28, 2022 9:50 pm Went looking for some books on machine language for the ZX80 & ROM deciphering.
This is the book for machine code on both ZX80 and ZX81.

http://www.users.waitrose.com/~thunor/m ... index.html
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
Moggy
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Moggy »

The ZX80 ROM disassembly can be found here...

https://k1.spdns.de/Vintage/Sinclair/80 ... source.txt
Creator
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Creator »

Received and installed the ZX8-CCB module but sadly there are issues. Seems my video signal is too low to properly drive the circuitry. Level is about 1.1v with or without the OEM circuit connected & about 1.4 v with nothing connected. ZX8-CCB paperwork says a 1.4v signal is needed. I don't have a schematic that shows what I need to look into this (circuit upstream from the ZX80 onboard video 'can'). A pointer to such if it exists would be appreciated. Other comments also welcomed.

EDIT : schematic found http://k1.spdns.de/Vintage/Sinclair/80/ ... matics.gif
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