ZX80 RAM PACK DIY clone
Re: ZX80 RAM PACK DIY clone
Speaking about heat sinks,
Does that heatsink on the 7805 look a little weird?
Does that heatsink on the 7805 look a little weird?
In theory, there is no difference between theory and practice. But, in practice, there is.
Re: ZX80 RAM PACK DIY clone
Yes it's quite unusual in this shape.
Re: ZX80 RAM PACK DIY clone
Oooh... That one looks beaten up. Is it still working though? And a weird heatsink indeed. Guess it won't hurt. Mine is running quite warm.
Just checked the PCB manufacturer and if I order 5 or more boards, the PCB costs around 9,60 euro. Toughest part is finding the 2114 RAM chips. I still have a few of these left.
Re: ZX80 RAM PACK DIY clone
Your W buttons are upside down! They should be pushed up through the bottom of the case I believe
Rich Mellor
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Re: ZX80 RAM PACK DIY clone
Awesome work - and looks pretty good!
Hope these pics help:
Hope these pics help:
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000
Re: ZX80 RAM PACK DIY clone
Thanks for that!
I think I may have found a similar rivet here:
http://www.essentracomponents.com/en-gb ... ter=5.8-mm
Requested a free sample, so let's see!
I do sell replacements for the ZX80 case rivets which may well be the same size...
But a free sample is even better
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Re: ZX80 RAM PACK DIY clone
Thanks! Actually got my original version today! And I am still surprised about the markings on the chips. Each 1K of RAM consists of 2 of these chips. One for the high nibble, the other for the low nibble. But why is one half done with an 2114LC and the other with a 2114LC-1. The -1 version has a 300ns access time, whereas the unmarked is 450ns. Same was done in the original ZX80.nollkolltroll wrote: ↑Thu Jun 01, 2017 5:31 pm A very nice expansion, extra credits for time-appropriate chips!
The only thing I can think of, is because of dataline D6' that is used in the NOP code generation during video display and has to be fast enough. That's probably also the reason why it is the only dataline with an additional pull-up resistor to speed it up a bit more. The slower device is less critical and was probably cheaper. Please correct me if I'm wrong
Time to test it and give it a nice bath of RetrObright..
Anyway, here are some side by side photos.
Re: ZX80 RAM PACK DIY clone
And I just noticed the RS logo on the 74LS138. Weird Never knew RS Components had their own 'brand' of logic devices. And no date code either. Fascinating...
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Re: ZX80 RAM PACK DIY clone
At one time RS branded their "RS" logo on all manor of electronic parts and equipment. I've got various chips and other parts with the RS branding.
Mark
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ZX81 Chip Pin-outs
ZX81 Video Transistor Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.