ZXmore - questions and answers (FAQ)

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
dessony
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Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Fri Nov 03, 2017 3:29 am

Hello Pokémon (Karl),
I bought a ZXmore V.1.2 from you. I transferred most of the components from the ZXmore v1.1 to new board and completed it. I hooked it up to a wall transformer and a monochrome monitor. A white screen showed up. No welcome screen yet! :cry: What should I do next?
Wm

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PokeMon
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Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Tue Nov 07, 2017 11:22 pm

Did you use the different CPLD ? (it needs another CPLD programming than the older ZXmore V1).
Did you check jumper settings ?
There are two mods, a 47pF capacitor on the underside and a solder bridge on the 74HCT74 between pin 1 and 2.

dessony
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Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Thu Nov 09, 2017 12:12 pm

IMG_0037.jpg
Back of the IC19 area.
IMG_0037.jpg (20.36 KiB) Viewed 199 times
IMG_0036.jpg
Back of the IC27 area.
IMG_0036.jpg (22.09 KiB) Viewed 199 times
I put the CPLD bearing its label ,"ZXmore V2-19 06/2017" in.

All jumpers are in its proper place in according to the page 8 of the ZXmore - notes for the construction kit, including NTSC jumper(J13).

Also, I burned an EEPROM with a MiniPro Programmer v6.60. This programmer's website can be web-linked to http://www.autoelectric.cn/EN/TL866_main.html .

I have an oscilloscope here.

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PokeMon
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Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Thu Nov 09, 2017 10:16 pm

What kind of CPU do you use ?
I had last time a problem with one UK customer here, using a chinese CPU rated to be a 20 MHz type but in fact it could not handle the 6.5 MHz (just labeled).

For a test you could also wire A16 (pin 2 of ROM/IC 4) to GND which would immediately start the ZX81 instance without ZXmaster. This uses less components on the board and the reduced speed with 3.25 MHz. This will bring up the blue led colour also.

dessony
Posts: 119
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Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Fri Nov 10, 2017 8:52 am

Good old American CPU! Zilog; Z84C0008PEG; Z80 CPU; 1506 XO

An A16 grounding test failed, I still see the white screen, no white "K" within black square yet. :( However, the LED turned blue on as soon as I did the A16 grounding test. After I took an end of a wire off, the multicolor LED was black.

I am considering about hooking up the ZXmore to my oscilloscope to check on its clock and video waves. Do you have any idea which another circuits on the computer do you want me to check it out?

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PokeMon
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Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Fri Nov 10, 2017 7:10 pm

Did you inspect the board for missing or bad solder joints carefully ?
When using this fix to the very first instance 1 (ZX81) then a few components are not in use.
Could you check the orientation of the resistor arrays ?
R1 and R4 have pin 1 to the keyboard direction while all the others have connectors direction.
R6 and R7 are not direction depended as single resistors are used.

Did you buy a complete construction kit or just the board kit and bought the most components yourself ?
You could send me high resolution pictures of both sides to info@ginger-electronic.com and I will take a look at it.
Maybe I find something suspicious.

It would be best to keep it started with pin 2 of ROM wired to GND as it reduces complexity.
You can remove the four 20 pin chips in the row near the keyboard and the 74HC590 and the RTC chip DS1302.
This will result in no keyboard reaction and a line pattern on screen only (like a barcode) but the system will start up and bring the cursor (not a K but a black square).

dessony
Posts: 119
Joined: Tue Oct 29, 2013 1:26 pm
Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Thu Nov 16, 2017 4:32 am

Pokémon (Karl),

Did you receive my recent email and a zippered video folder from me? These data were sent to info@ginger-electronic.com.

I might start tracing a few tracks related to ROM since I only see a bright white screen and nothing another else. Please correct me if I am wrong.

ThanX,
Wm

Shaun_B
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Re: ZXmore - questions and answers (FAQ)

Post by Shaun_B » Fri Nov 17, 2017 7:25 am

Hi PokeMon,

I contacted you on Sell My Retro about an issue that I'm having.

My ZXMore still won't boot to the master/welcome screen. I tried removing the battery and putting it back in and I'm now getting a white screen and nothing else (after a brief flash of the on board LED from blue to nothing).

As I said in my message, it worked for a while but now has stopped working. Yesterday evening was the first time that I could test it as I had to wait to get a power supply with the correct connection which I had to order online and collect.

Regards,

Shaun

dessony
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Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Fri Nov 17, 2017 10:06 am

Pokemon and Shaun,

With an oscilloscope, I could see a few video back porch waves and a few clock square waves from the Z80's pin number 6. Did you see these waves on your own board?

Shaun, is your screen showing only steady white screen? If so, then it is the same thing as mine. :cry:

Thanks,
Dessony

Shaun_B
Posts: 310
Joined: Wed Apr 22, 2009 9:22 am

Re: ZXmore - questions and answers (FAQ)

Post by Shaun_B » Fri Nov 17, 2017 2:26 pm

Yes my ZXMore initially had a black screen (after working for a while, I should say).

I removed the battery and put it back in (thinking that might do some sort of reset on the system or something, obviously after unplugging the PSU). And then I got a white static screen, nothing else on power up.

This is after plugging it in and a quick flash of the on-board LED.

Thanks,

Shaun

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