Lardo buys another zeddy

ZX80 / ZX81 hardware and software offered for sale or swapping
Lardo Boffin
Posts: 1283
Joined: Sat Nov 26, 2016 2:42 am

Re: Lardo buys another zeddy

Post by Lardo Boffin »

So its been a while for a zeddie... Or two.

7A412896-08B8-4F9D-8FFC-FB4DE7F74D07.jpeg

An early, bugged ROM issue one.
5E9BDCDD-91D8-4108-8F07-D662CAB6B5EF.jpeg

And a later, non-bugged ROM issue one.
B674A55A-1C4F-4225-8F11-1426AEFABB1F.jpeg
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Spectrum +2a
Lardo Boffin
Posts: 1283
Joined: Sat Nov 26, 2016 2:42 am

Re: Lardo buys another zeddy

Post by Lardo Boffin »

A very nice boxed working issue 3. Won’t be able to do much with it for a while though - I have run out of ZX8-CCBs.

35FC8D25-EA2F-499A-BD47-0B46C33A4CCD.jpeg
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Spectrum +2a
User avatar
1024MAK
Posts: 3140
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Lardo buys another zeddy

Post by 1024MAK »

Ahh, one with a stick on hard key keyboard.

I had a Zeddy with one of those, but the stick on hard key keyboard fell off! :lol:

Mark
Moggy
Posts: 2082
Joined: Wed Jun 18, 2008 2:00 pm

Re: Lardo buys another zeddy

Post by Moggy »

Lardo Boffin wrote: Mon Jun 08, 2020 12:05 pm A very nice boxed working issue 3. Won’t be able to do much with it for a while though - I have run out of ZX8-CCBs.


35FC8D25-EA2F-499A-BD47-0B46C33A4CCD.jpeg
At this point Pokemon sighs and tells his wife he will be working late as Lardo has run out of video boards. :lol:

Looks good by the way but that early filesixty is a bugger to keypress compared to the later neoprene version.
Lardo Boffin
Posts: 1283
Joined: Sat Nov 26, 2016 2:42 am

Re: Lardo buys another zeddy

Post by Lardo Boffin »

Moggy wrote: Mon Jun 08, 2020 2:12 pm
Lardo Boffin wrote: Mon Jun 08, 2020 12:05 pm A very nice boxed working issue 3. Won’t be able to do much with it for a while though - I have run out of ZX8-CCBs.


35FC8D25-EA2F-499A-BD47-0B46C33A4CCD.jpeg
At this point Pokemon sighs and tells his wife he will be working late as Lardo has run out of video boards. :lol:

Looks good by the way but that early filesixty is a bugger to keypress compared to the later neoprene version.
Sadly (for me at least) his shop is shut! My last batch of 5 ‘ccbs ran out a couple of weeks ago. First world problems I guess.

I just noticed that about the keyboard - it needs a lot of pressure!
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Spectrum +2a
Moggy
Posts: 2082
Joined: Wed Jun 18, 2008 2:00 pm

Re: Lardo buys another zeddy

Post by Moggy »

Lardo Boffin wrote: Mon Jun 08, 2020 2:36 pm
Moggy wrote: Mon Jun 08, 2020 2:12 pm
Lardo Boffin wrote: Mon Jun 08, 2020 12:05 pm A very nice boxed working issue 3. Won’t be able to do much with it for a while though - I have run out of ZX8-CCBs.


35FC8D25-EA2F-499A-BD47-0B46C33A4CCD.jpeg
At this point Pokemon sighs and tells his wife he will be working late as Lardo has run out of video boards. :lol:

Looks good by the way but that early filesixty is a bugger to keypress compared to the later neoprene version.
Sadly (for me at least) his shop is shut! My last batch of 5 ‘ccbs ran out a couple of weeks ago. First world problems I guess.

I just noticed that about the keyboard - it needs a lot of pressure!
Damn I didn't know that he had shut down. Pity it isn't a later back porch ULA then at least you could do the transistor mod. :(
Lardo Boffin
Posts: 1283
Joined: Sat Nov 26, 2016 2:42 am

Re: Lardo buys another zeddy

Post by Lardo Boffin »

Moggy wrote: Mon Jun 08, 2020 2:40 pm
Lardo Boffin wrote: Mon Jun 08, 2020 2:36 pm
Sadly (for me at least) his shop is shut! My last batch of 5 ‘ccbs ran out a couple of weeks ago. First world problems I guess.
Damn I didn't know that he had shut down. Pity it isn't a later back porch ULA then at least you could do the transistor mod. :(
It produces a reasonable and bright picture on my CRT telly although as I type it gets worse. I will try and tune it a bit in the modulator (it has helped on occasion) but if not I may need to give it a go. Do you have a link please?
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Spectrum +2a
Moggy
Posts: 2082
Joined: Wed Jun 18, 2008 2:00 pm

Re: Lardo buys another zeddy

Post by Moggy »

Hi Lardo.

This is perhaps the most simple transistor mod (see picture) and also Mark has a superior design that can be found in his signature. On the output it's recommended to add a 100uf,at least 16Volt rating, electrolytic cap(+ side facing the transistor) for DC blocking although most TV's already do that, better safe than sorry. For the 100ohm resistor I use a variable one as the tiny road-star TV I use overloads terribly with normal settings and bleeding more of the signal to earth/ground helps enormously.

This can be made up on a piece of Vero board with the same four wire (video in-5volt-video out-earth) setup as karls video board jobby and mounted in side the modulator(if removing original c/board) in the same manner using the modulators power and video feed from the motherboard after de-soldering the modulators own feed wires and using the modulators output socket .

However this setup does not produce a back porch signal and is really only any good with the later 210 ULA's as far as colour CRT TV's are concerned though ok with B/W.

Also for the transistor I find that if you have a scrap 81 motherboard with no hope of redemption then either of the two onboard transistors work perfectly for this application.

The board looks a little like this example but imagine an extra cap on board(not sure why the 5th wire is added in this example).
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Lardo Boffin
Posts: 1283
Joined: Sat Nov 26, 2016 2:42 am

Re: Lardo buys another zeddy

Post by Lardo Boffin »

Thanks Moggy!
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Spectrum +2a
User avatar
1024MAK
Posts: 3140
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Lardo buys another zeddy

Post by 1024MAK »

:arrow: ZX81 Video Transistor Buffer Amp ;)

There is also a design using a NE555 timer chip to generate a pulse for the back porch. I’m not tried it. Alternatively, there is the ZXVid.

Mark
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