It’s part two! I honestly gave up trying to fix this machine multiple times. But something just kept making me come back for more. Rest assured there are hours of footage I edited it off this, with a huge amount of work performed off camera too. And this one was supposed to be easy!

In this video, I build a dedicated Z80 CPU tester to help diagnose failed processors found during recent ZX81 and Spectrum repairs. This project focuses on identifying original NMOS versus later CMOS variants, which differ in power consumption, heat production, and undocumented behaviour. The build uses a red PCB from PCBWay and includes an SMD resistor modification to fit a specific footprint. After assembly, I test various Z80s from my parts bins, identifying several dead chips and units with simple bent pins. Important Note on the Current Jumper: The current jumper must be installed by default for the tester to function. While the instructions suggest removing it to measure current with a multimeter, the device will not run or show test activity without the jumper in place. Tester Limitations: This tool primarily exercises address lines using a small test program. Some complex faults, such as issues with the HALT line or other specific inputs/outputs, still require advanced diagnostic tools like the Backbit Chip Tester Pro

How far should you go when repairing a “reluctant” computer? We are about to find out! This ZX Spectrum, from the pile of computers that Paul Universal Retro Boss supplied for repair content, is very poorly. Black and white bars on the screen are not a great clue and diagnostics doesn’t help much either. So join me as I start the deep dive into this sick example of a ZX Spectrum 48k.

In this video, I repair two Sinclair ZX81 computers provided by Paul Universal Retro Boss. Both units arrived with white screen issues, which initially seemed like simple candidates for composite modifications. The diagnostic process for the first unit involved cleaning heavily corroded SRAM legs and troubleshooting a lack of bus activity. I ultimately identified a failed Z80 CPU. After replacing the processor and installing a composite mod board with a 555 timer, the machine was fully restored. The second unit exhibited similar symptoms, including a halted CPU. Swapping the Z80 processor fixed this unit as well, confirming that both computers suffered from bad silicon rather than ULA failure. I also test the original keyboard membranes and discuss challenges with modern capture devices as well as vintage 16K RAM packs.

There is something very special hiding in this ZX Spectrum+ case. Its also broken, which in my eyes just makes it more special and interesting!

Is your Commodore 64 literally falling apart at the seams? You aren’t alone. As these iconic machines hit their 40th anniversary, the ABS plastic is becoming notoriously brittle. Snapped screw posts and broken case clips are often the “death sentence” for a Breadbin… until now.

A rare computer (ZX Spectrum 128k “Toastrack”) inside a rare replacement keyboard (Saga 2+). What are the chances there is another one quite like this out there in the world? I will probably see my inbox full of these pretty soon.

I love rummaging around in jumble sales for bargains. Make that jumble sale happen in a superb computer museum with loads of friends from the community and fill it with stacks of super cheap (for the most part) vintage computer and retro gaming bargains and I am as happy as Larry.

The third KU-14194HB board with capacitor juice damage is up for repair. More bad traces in this one and another fault that made me scratch my head for quite some time!

Another C64 with leaking cap damage. This one a more rare board. Prepare yourself for lots of scraping traces and nasty green goo.