Sinclair ZX80 / ZX81 / Z88 Forums

The fun has begun...

As my late father used to say "Now there's a thing of service".

Moggy wrote: ↑Sat Jun 03, 2017 5:27 pm As my late father used to say "Now there's a thing of service".

Well said!
And it is alive! Haven't hooked it up to a screen yet, but I can see a composite signal! Probed around a bit and everything looks okay. Weird thing is it's only drawing 275mA while my original one draws well over 400mA. The only difference is that I am using a CMOS Z80. But I didn't expect that it would make such a difference. Maybe the electrolytic caps need replacement on the original one?

Anyway, next up is to fit the keyboard membrane from Rich (well done!) and swap the CCB to the clone. And I have to find a piece of aluminium (damn spelling checker tried to change that into aluminum ) and turn it into a heat sink. Make an EPROM with both ZX80/ZX81 firmware.

Any found one error so far. Holes for the ear/mic/pwr sockets are a bit to small.

Yep, definitely alive! Even works with the ZX80 RAM pack clone. Last post for today

Great stuff MaFli another one lives!

Seeing as you are fitting a multi-ROM then I assume modding versus originality doesn't worry you.
In which case why not fit a switching regulator and keep it all nice and cool?

The CMOS CPU does make a difference and I would say your power usage without memory pack seems about right.

I have probably mentioned this in other threads but here's a link for regulator anyway and again fantastic job.

http://uk.rs-online.com/web/p/switching ... s/6664379/

@MaFli - nice work

Mark

MaFli wrote:Weird thing is it's only drawing 275mA while my original one draws well over 400mA. The only difference is that I am using a CMOS Z80. But I didn't expect that it would make such a difference.

The Zilog Z80 data sheet gives the Icc supply current as 200mA for the NMOS z80 vs. 20mA (at 4MHz) for the CMOS Z80.

MaFli wrote:Maybe the electrolytic caps need replacement on the original one?

What, all two of them! C10 is used for the CPU reset, so uses very little current. C8 lives near the heatsink though.

Mark

Moggy wrote: ↑Sun Jun 04, 2017 12:44 pm Great stuff MaFli another one lives!

Seeing as you are fitting a multi-ROM then I assume modding versus originality doesn't worry you.
In which case why not fit a switching regulator and keep it all nice and cool?
The CMOS CPU does make a difference and I would say your power usage without memory pack seems about right.
I have probably mentioned this in other threads but here's a link for regulator anyway and again fantastic job.
http://uk.rs-online.com/web/p/switching ... s/6664379/

Yes, thanks. I remember you suggesting me that one.
I'm not too worried about originality indeed. It's a clone and very very close to the original, but it is still a clone
If I use my bench supply set at 9V it remains quite cool. With a Sinclair supply it gets bl##dy hot
So I'll probably do as you suggested and fit some kind of switching regulator. Another user suggested this one:
http://power.murata.com/data/power/oki-78sr.pdf Basically the same thing, but more of a bare board version.

1024MAK wrote: ↑Sun Jun 04, 2017 1:30 pm @MaFli - nice work
The Zilog Z80 data sheet gives the Icc supply current as 200mA for the NMOS z80 vs. 20mA (at 4MHz) for the CMOS Z80.
What, all two of them! C10 is used for the CPU reset, so uses very little current. C8 lives near the heatsink though.
Mark

Thanks! Just desoldered all (...) of them. I have a decent LCR meter and they are still fine. I'd like to keep the original as original as possible, so I'll stick these back in for now. Weird choice to place it so close to the heatsink. Sinclair's mysterious ways...

Hi

Get please send gerber file from zx80 pcb
Sorry my english is bad

Thanks

MaFli
Is possible to send me gerber files?