ZX80 Core - new ZX80 motherboards

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
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PokeMon
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Re: ZX80 Core - new ZX80 motherboards

Post by PokeMon » Thu Jun 12, 2014 7:46 pm

Hmm - let me check this - would explain something.
I think the EEPROM should be write protected.
In my datasheet the enable sequence is:

WRITE ($1555),$AA
WRITE ($0AAA),$55
WRITE ($1555),$A0

I am not sure if there is a difference wether using 28C64 and 28C256.
I do not write protect it again - thought this is automatically write protected.
But unsure now. :shock:

poglad
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Re: ZX80 Core - new ZX80 motherboards

Post by poglad » Thu Jun 12, 2014 9:28 pm

It is different. On the 28C256 it's $5555 rather than $1555. No idea whether it write protects again, but there seem to be no options for sending these codes through the GQ USB software, unfortunately.

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PokeMon
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Re: ZX80 Core - new ZX80 motherboards

Post by PokeMon » Thu Jun 12, 2014 9:55 pm

Unfortunately you are right.
I did send you my program algorithm via email which is quick and dirty now.
I will provide a more useful version for programming in summer.
You could adapt it for you own purposes in the meantime or develop a nice tool yourself, if you like. ;)

poglad
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Re: ZX80 Core - new ZX80 motherboards

Post by poglad » Thu Jun 12, 2014 10:33 pm

Thanks Karl, looking forward to giving it a go! :)

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blittled
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Re: ZX80 Core - new ZX80 motherboards

Post by blittled » Tue Aug 19, 2014 3:11 am

I have an odd thing happening with my ZX80 Core. At a random point when I'm playing a game the screen blacks out and the only way to get the ZX80 core working is a reset. If the ZX80 Core is just sitting there it happily keeps going. I loaded Mazogs and it sat there for an hour displaying the intro but 5 minutes into playing it the screen goes black. I've tried different power supplies at different voltages such as 6, 7.5 and 9 volts. I am using a LDO regulator so the bare minimum voltage it can operate on is 6V.

I'll probably have to get my oscilloscope out and check the video out, clk and data bus to see what's happening. Any ideas on what may be causing this? Maybe it is a special Ram Pack wobble feature? :)
2X Timex Sinclair 1000, ZX81, ZX80Core, 5X 16K Ram Pack, ZXBlast, ZX P file to Ear Input Signal Converter, Elf II

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PokeMon
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Re: ZX80 Core - new ZX80 motherboards

Post by PokeMon » Tue Aug 19, 2014 1:51 pm

Hmmm could be maybe some loose contact, an unsoldered or bad soldered pin, a bad socket (if you are using sockets), something like that.
So as I understood, it is not happening when it is still laying down but using it/the keyboard/mechanical stress.

I would first inspect the backside carefully, especially any socket on the top side.
I would prefer to use sockets with precision contacts only.
Then I would try to press or knock softly on every IC while a program is running.
Even the keyboard.

And you could do a bending test of the board (soft, not to hard) to see if there are any contact problems.
You should wear some isolating gloves but not plastic to avoid inductions with your fingers but also to avoid electrical discharge which could destroy ICs.
So leather gloves would be good enough I think.

Did you solder R100 to the EEPROM ? Depends on which version you have (V1.0 2013 or V1.1 2014).
If you are able you could also try to take another EEPROM or to burn it new or to burn an EPROM instead.

Do you use a case ? It should be best non electrical / non metal.

So these are my first hints to get deeper into this problem.

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blittled
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Re: ZX80 Core - new ZX80 motherboards

Post by blittled » Wed Aug 20, 2014 6:23 pm

Pokemon, Thanks for the info. You are probably right that it is a bad solder connection. I'm busy for probably the next month. When I get a chance I'll check it out and post what I find.
2X Timex Sinclair 1000, ZX81, ZX80Core, 5X 16K Ram Pack, ZXBlast, ZX P file to Ear Input Signal Converter, Elf II

XorA
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Re: ZX80 Core - new ZX80 motherboards

Post by XorA » Mon Apr 30, 2018 10:03 pm

Finally got back to trying to repair my 1.0b board. And I see all the docs/rom image seem to have dissapeared :-(

XorA
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Re: ZX80 Core - new ZX80 motherboards

Post by XorA » Tue May 01, 2018 11:06 am

Found the manual in my backup for 1.1 board.

But Im puzzled, I seem to be getting pixel data but no sign of sync pulses.

Edzard
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Re: ZX80 Core - new ZX80 motherboards

Post by Edzard » Tue Jun 25, 2019 4:34 pm

Hallo,

Is it still possible to obtain a PCB?

Thanks,


Edzard

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