ZXmore or the ZX80CORE follow-up

[superfo]

You may be right in this point.
But I think there is no particular reason for making the body wider than necessary except an historical.
This is just a waste of space even when it's a common practice.

I forget the real reason, it looks like they want to use the same lead frame size for both 14 and 16 pin package.
you can see that for 16 pin package, pin 1, 8, 9, 16 is smaller than other pins while for 14 pin package every pin has the same size.

[PokeMon]

Well 20 pin dip packages or 8 pin dip packages are that small as 16 pin.
So this must be a relict from the beginning of TTL, I think.

[1024MAK]

Making progress

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Mark

[1024MAK]

Nearly there...

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Now have to wait for the soldering iron to cool down to finish soldering the phono/RCA/Chinch socket and the metalwork of the USB connector. But it's late, so that can wait for tomorrow.

Mark

[1024MAK]

It lives

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A working ZXmore :-)

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Boot screen

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ZX81 mode

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Ignore the coloured patterning, that's an artefact between the monitor (LCD TV) and the camera and maybe the LED lighting. Not seen this effect this bad when I have taken pictures before, so will have to try again tomorrow and see if I can work out why.

A nice kit, thanks Karl

Fitting the regulator: First I did a test fit on the underside of the board to work out where to bend the legs. A nice set of smooth flat nose pliers is great for this. Then, instead of trying to insulate the 0V/GND "via" under the regulator heatsink, instead I put a M3 machine screw through from the underside of the board. Then put a bright plated plain steel washer on the top side of the board over the threaded machine screw. Then applied solder to the edge of the washer and the PCB "track" on the regulator legs side of the washer. This then held the washer in place. The heatsink and the regulator where then fitted, and then secured with a M3 nut. Finally, after tightening the machine screw and nut, I soldered the regulator pins in place. The washer creates a nice gap so that the heatsink does not touch the"via".

Note that the machine screw supplied in the kit is a little too short for this, so I used a slightly longer one. I think I used a 6mm pan head type, but it may have been a 10mm one.

Mark

[1024MAK]

I should add that the washer has to be soldered, otherwise it could move and touch the "via" itself, just.

Mark

[PokeMon]

Thanks for the hints.
Now the supplied screws are a bit longer (2mm). The other ones have been measured out exactly to give the customer not too much clearance.

I am not sure what a washer is - this here ?


By the way - I am now working on the next release with flash programming of ROMs and a configuration tool as well as implementing SAVE on USB an some more features. And any bugs let me know to fix them right in the next version.

[Andy Rea]

i have a question, what is the purpose of the 2 diodes around the regulator ? i have seen it done to say use a 5V Regulator to get 6V instead but i don't quite get why your raising it and then lowering it again with another diode on the output.

also i don't seem to be able to use my sound-card on the edge connector, ZXmore fails to boot.

Regards Andy

[PokeMon]

The purpose of the 2 diodes is decoupling the voltage regulator when the board is powered via USB with a USB power supply for example.
Nothing more.

Regarding your soundcard - is there maybe a conflict with the IO addresses used from ZXmore by default addresses 0x7C-0x7F ?

Karl

[1024MAK]

Karl beat me to it. But I will post anyway...

The diodes are there so that you have the option of using a normal PSU or using a 5V USB type PSU.
The signal diode raises the regulators output by one diode volt drop, which compensates for the diode in series with the output from the regulators output terminal. Hence the +5V rail is still at +5V

Mark