Time to go back in time again - ZX80 replica build

[HigashiJun]

@rubber_jonnie

Yes, it's a big step forward.

[rubber_jonnie]

@rubber_jonnie

Yes, it's a big step forward.

:D

[stephen_usher]

Yay! More likely 10K would be better for TTL chips.

[rubber_jonnie]

Yay! More likely 10K would be better for TTL chips.

It was late when I did this, I may have tried 10K and it didn't work. I need to do a bit more work to find out what works best.

[rubber_jonnie]

And we're there:

IMG20251007002132.jpg

Interestingly IC11 died and on replacement I got this.

Perhaps IC11 was marginal all along. Will test the old ic tomorrow but it got very hot all of a sudden. New one is cool as a cucumber.

:girldance:

Time for bed...

[HigashiJun]

:cheer: :yay2: :cheer: :yay2: :cheer:

Have a good night !

[rubber_jonnie]

:cheer: :yay2: :cheer: :yay2: :cheer:

Have a good night !

:lol:

Took me ages to get to sleep as I was a bit pumped :dizzy:

[stephen_usher]

Yay! What was IC11, a flip-flop?

[rubber_jonnie]

OK, the ZX80 is done!!!

:girldance: :girldance: :girldance:

So, it turns out that IC 11 was marginal, and it must have been throwing things off. It did test OK earlier in the process, but last night got really hot, and now it's dead:

IMG_20251007_091912.jpg

Here it is running with a new IC11, a 74LS00:

IMG20251007002132.jpg

IMG20251007091809.jpg

IMG20251007091832.jpg

I'm not sure what the grey fuzzy bits on the screen shots are, seems to be a camera artifact as they aren't there in real life.

In addition to the replacement for IC11 I did also need to slightly increase the value of R25 from 470R to 680R, otherwise no picture, but that was all it took. I was able to hook up a pot and adjust it until the display was nice, then measure that for the value.

Here's the Z8-CCB installed in the modulator can:

IMG20251007091727.jpg

And some gratuitous shots of the machine itself:

IMG20251007091502.jpg

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And with it's brother:

IMG20251007094236.jpg

And hooked up an old stylee to a little B&W (This is a cheat as it has composite but I don't care :) )

IMG20251007095407.jpg

I'd forgotten what fun taking pics of CRTs was...

Pretty happy with the overall result. You could argue it's not fully complete as I have't tested the mic and ear sockets yet, but it's good enough to come with me to CL4 :)

[rubber_jonnie]

Quick lunchtime mod. Inverse video :)

I added some wires to the 'inverse video' pads on the Z8-CCB board and routed them out to a jumper by the mic/ear.

IMG20251007135603.jpg

IMG20251007135620.jpg

And jumper on gives me inverse video. Jumper off:

IMG20251007135640.jpg

And jumper on:

IMG20251007135658.jpg

Only just completed and modded already :) And no, it doesn't interfere with the mic/ear sockets :)