Hi all
So I bought another zeddy as spares/repairs on Ebay for a bit of tinkering with the intention of adding a composite mod and internal 16K RAM upgrade. However, when I opened it up to take a look I found that it was an early version with the stand-off board on the Z80 to rectify a ROM error as discussed here and on pictures attached:
viewtopic.php?f=7&t=1387
I gather that only 20,000 of these were produced back in the day, so I guess it's quite rare now. Anyway, I fired it up with temporary connections to the composite mod and up came the K prompt with a good clear picture. The keyboard appears original and works fine too.
So that led me to thinking, should I leave this zeddy as is and maybe sell it on to someone looking for a rarer version and get another one to tinker with rather than potentially damaging it with my "upgrades"?
All opinions gratefully received.
Dave
What to do with an unusual ZX81?
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Re: What to do with an unusual ZX81?
I have come across a few of these but haven’t ever refurb’d one. Not ridiculously rare but I wouldn’t change one other than any necessary repairs.
There are probably a few in here!
https://www.sinclairzxworld.com/viewtop ... f=8&t=3312
There are probably a few in here!
https://www.sinclairzxworld.com/viewtop ... f=8&t=3312
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: What to do with an unusual ZX81?
My own personal view is there are more users than collectors out there, myself included. The kludged ones are still deficient ROM wise and any I have come across over the last forty odd years I have happily rejigged. Improve the bugger and let someone enjoy it as it was meant to be enjoyed without worrying about floating point errors and a lousy TV picture.
As far as collectability goes they are Hardly a Rembrandt or Ferrari so no pension plan there, just a simple old 8 bitter wanting one last day in the sun so improve it and set back in the wild, earning its salt rather than sat in some some bods glass cabinet.
Just my thoughts on it and appreciate that others may think differently.
As far as collectability goes they are Hardly a Rembrandt or Ferrari so no pension plan there, just a simple old 8 bitter wanting one last day in the sun so improve it and set back in the wild, earning its salt rather than sat in some some bods glass cabinet.
Just my thoughts on it and appreciate that others may think differently.
- 1024MAK
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Re: What to do with an unusual ZX81?
Hmm, being the electronics nerd that I am, I was thinking that those are a useful source of a couple of 74 series logic chips...
Mark
PS i have plenty of run of the mill issue 1 and issue 3 boards to tinker with. A long time ago in a universe far, far away, I bought around 5 not working, for spares/repairs" issue 1 Zeddies from a seller for not a lot of money. It turns out these were from an educational place and apart from the normal keyboard faults, most had simple faults, like the ROM being placed incorrectly in the socket.
Mark
PS i have plenty of run of the mill issue 1 and issue 3 boards to tinker with. A long time ago in a universe far, far away, I bought around 5 not working, for spares/repairs" issue 1 Zeddies from a seller for not a lot of money. It turns out these were from an educational place and apart from the normal keyboard faults, most had simple faults, like the ROM being placed incorrectly in the socket.
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
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Re: What to do with an unusual ZX81?
Ah, but isn't this the point where the ones which do survive become more valuable because everyone at the time said 'Nah, nothing special...'. Looking into my crystal ball 20 years from now I can imagine people saying 'Do remember that peculiar mod they did to fix the ZX81 ROM, classic 1980's stuff!. Pity nobody preserved an original one'.
Re: What to do with an unusual ZX81?
Thank you all for your thoughts - some mixed views, a bit like my own mixed feelings It's a peculiar bit of computing history really, I don't suppose Apple, Dell or Lenovo would let a product out of their factories looking like that nowadays
Maybe I'll just do the composite mod so that it can still be used but without changing anything drastic, just a couple of snipped wires leaving all of the video gubbins in place and use it with an external ram pack. Like 'ones complement' says there won't be many survivors to tell the story of eccentric British computer companies if they all get modded!
Dave
Maybe I'll just do the composite mod so that it can still be used but without changing anything drastic, just a couple of snipped wires leaving all of the video gubbins in place and use it with an external ram pack. Like 'ones complement' says there won't be many survivors to tell the story of eccentric British computer companies if they all get modded!
Dave
- 1024MAK
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- Location: Looking forward to summer in Somerset, UK...
Re: What to do with an unusual ZX81?
If it's any help, the ZX Spectrum issue 1 (and some early issue 2) boards that have a different "dead bug" daughter board tend not to be modified (unless they were back in the day).
You don't need to snip any wires. Just desolder the two wires going into the modulator from the PCB and secure them so they don't touch anything else.
Mark
You don't need to snip any wires. Just desolder the two wires going into the modulator from the PCB and secure them so they don't touch anything else.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor 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 being good this year.
Re: What to do with an unusual ZX81?
Good point, thanks Mark.