Sinclair ZX80 / ZX81 / Z88 Forums

Speaking about heat sinks,
Does that heatsink on the 7805 look a little weird?

Yes it's quite unusual in this shape.

1024MAK wrote: ↑Thu Jun 01, 2017 12:43 am Ooh, an offer of more hardware goodness. I need a partner for this...

So, yes, I would be very interested

Mark

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.

1024MAK wrote: ↑Thu Jun 01, 2017 12:43 am Ooh, an offer of more hardware goodness. I need a partner for this...IMG_4648.JPG

So, yes, I would be very interested

Mark

Your W buttons are upside down! They should be pushed up through the bottom of the case I believe

Awesome work - and looks pretty good!

Hope these pics help:

Fwapp wrote: ↑Thu Jun 01, 2017 3:37 pm Awesome work - and looks pretty good!
Hope these pics help:

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

A very nice expansion, extra credits for time-appropriate chips!

nollkolltroll wrote: ↑Thu Jun 01, 2017 5:31 pm A very nice expansion, extra credits for time-appropriate chips!

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.
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.

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...

MaFli wrote: ↑Fri Jun 02, 2017 6:19 pm 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...

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