Sinclair ZX80 / ZX81 / Z88 Forums

1024MAK wrote: ↑Sat Jun 13, 2020 8:29 pm 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

I thought I had already pointed out your design in your signature.

I popped the case and it is very shiny!

ULA 2C210E.

Moggy wrote: ↑Sat Jun 13, 2020 10:42 pm I thought I had already pointed out your design in your signature.

You had, but I thought it worthwhile copying said link into a post so that it was crystal clear

Mark

I have adjusted the pot in the modulator and it helps but not enough. Guess I may have to try a transistor mod!
The ZXVid is great but a bit expensive to be able to then sell this on.

Do it lardo you know you want to.

Moggy wrote: ↑Sun Jun 14, 2020 2:12 pm Do it lardo you know you want to.

I have a plan! It involves a weasel.

Or at least stealing the ZX8-CCB from my test rig and putting it in this zeddy and then making one of the comp mods shown and putting it in my test rig.

God that's a cunning plan if ever I heard one!

Moggy wrote: ↑Sun Jun 14, 2020 6:38 pm God that's a cunning plan if ever I heard one!

And done!

I had cut the cables a bit shorter to fit inside my test rig so was faced with a dilemma - fit new cables (eyesight issues with that) or not fit it where I would normally fit.

So I went with option 2.


There are no clearance issues and the red and black cables are fine when routed properly. The board (yes its a green one, thats how old my test rig is / was!) is held by a very strong piece of double sided foam.

Any chance of interference from the PCB? The picture seems rock solid so far.

I also noticed this once I opened the case:


Where is the solder holding the modulator in place?

Lardo Boffin wrote: ↑Mon Jun 15, 2020 12:00 am Where is the solder holding the modulator in place?

You should write to Sinclair and ask them?

Mark

1024MAK wrote: ↑Mon Jun 15, 2020 9:33 am

Lardo Boffin wrote: ↑Mon Jun 15, 2020 12:00 am Where is the solder holding the modulator in place?

You should write to Sinclair and ask them?

Mark

No need for that.

I happen to know that at the time when most companies were turning to lead free solder Timex decided on a more rigorous strategy of using solder free solder and as you can see it works wonderfully.

Having drunk more whisky than usual so early Moggy retires to his settee for a long nap.