Lardo buys another zeddy

[Lardo Boffin]

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

An early, bugged ROM issue one.

And a later, non-bugged ROM issue one.

[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.

[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!

Mark

[Moggy]

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.

Looks good by the way but that early filesixty is a bugger to keypress compared to the later neoprene version.

[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

At this point Pokemon sighs and tells his wife he will be working late as Lardo has run out of video boards.

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!

[Moggy]

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.

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]

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?

[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).

[Lardo Boffin]

Thanks Moggy!

[1024MAK]

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