Here's a ZX80 I pick up off ebay about a year ago. It was sold as non-working/condition unknown and without a case.
Still even for a non-runner £45 is a bargain, even if I include any replacement parts.
![Image](https://live.staticflickr.com/1910/44731336075_783543eeee_4k.jpg)
First, the obvious issues. The ceramic resonator X1 is missing.
![Image](https://live.staticflickr.com/1962/45594986622_aa8a8d84dc_4k.jpg)
I have replacement resonators and have also bought a crystal oscillator. I've yet to decide which way to go as regards which one I'll fit.
Secondly one of the 74LS157 multiplexer's is actually cracked right across the package
![Image](https://live.staticflickr.com/1922/45594985272_cb6fca92f9_4k.jpg)
These first two issues are easily solved. However of more serious concern is the EPROM.
![Image](https://live.staticflickr.com/1906/44731334255_f68be31381_4k.jpg)
As you can see the protective cover that should be over the quartz window, is protecting nothing. Now although these types of EPROM's can retain their programming for decades, we all know that exposure to UV light of any source wille eventually erase the contents. I have no knowing how the machine was stored before I came by it, I.e. was it kept in darkness out of the sun or other UV light source.
It's not a total disaster though as have several diffrent EPROM programmers that will reprogram this version of EPROM used in the ZX80, and if the device is faulty it's not too bigger problem as I collect old IC's, processors and EPROM's and I'm sure in my largish collection of EPROM's I will have a suitable replacement. First off though I'll insert the device into one of my programmers to see if it can read back any of its contents. This will give me an idea if the ROM is still viable.
The repair of this machine was started about six months ago, unfortunately some of the other retro computers I have bought have taken a bit more priority.
In the next part I'll detial how I replaced the damaged 74LS157.
Regards
Andy