Uploaded June 2026 | Updated September 2026, 2 weeks ago
Special thanks to PCBWay for sponsoring this video.
pcbway.com
Today I have a rubber key 48K ZX Spectrum issue 3B on the bench. This particular motherboard is an unusual dark green color, manufactured in Korea, and it arrived with a completely dead data bus.
Using a diagnostic card and an oscilloscope, I trace the power, clock, and reset signals to figure out why the system refuses to boot. After ruling out the ULA, the focus shifts to the Z80 CPU. I remove the original processor, test a replacement, and install it to see if that resolves the erratic data lines.
Once the repair is done and the display is stabilized with a composite mod, I test the system with a quick run of Manic Miner.
─────────────────────────────
If you'd like to help keep the lights on (and the tools plugged in),
my Patreon is the best way to do it. Patrons get ad-free early access
to videos, behind-the-scenes updates, and entry to a super secret
Discord channel — plus my sincere gratitude, which is worth roughly
what you'd expect.
▸ Patreon: patreon.com/c/morefunmakingit
─────────────────────────────
I also have another channel called More Fun Making It, where I build
things from scratch instead of trying to coax life back into them.
Same shed, different end of the workbench.
▸ More Fun Making It: youtube.com/@MoreFunRetro
─────────────────────────────
There's also the Retro Hardware Discord, where people who enjoy this
sort of thing gather to talk about it. It's better than it has any
right to be.
▸ Retro Hardware Discord: discord.gg/ChH726tbbF
─────────────────────────────
#ZXSpectrum #RetroComputing #Z80
Special thanks to PCBWay for sponsoring this video.
pcbway.com
Today I have a rubber key 48K ZX Spectrum issue 3B on the bench. This particular motherboard is an unusual dark green color, manufactured in Korea, and it arrived with a completely dead data bus.
Using a diagnostic card and an oscilloscope, I trace the power, clock, and reset signals to figure out why the system refuses to boot. After ruling out the ULA, the focus shifts to the Z80 CPU. I remove the original processor, test a replacement, and install it to see if that resolves the erratic data lines.
Once the repair is done and the display is stabilized with a composite mod, I test the system with a quick run of Manic Miner.
─────────────────────────────
If you'd like to help keep the lights on (and the tools plugged in),
my Patreon is the best way to do it. Patrons get ad-free early access
to videos, behind-the-scenes updates, and entry to a super secret
Discord channel — plus my sincere gratitude, which is worth roughly
what you'd expect.
▸ Patreon: patreon.com/c/morefunmakingit
─────────────────────────────
I also have another channel called More Fun Making It, where I build
things from scratch instead of trying to coax life back into them.
Same shed, different end of the workbench.
▸ More Fun Making It: youtube.com/@MoreFunRetro
─────────────────────────────
There's also the Retro Hardware Discord, where people who enjoy this
sort of thing gather to talk about it. It's better than it has any
right to be.
▸ Retro Hardware Discord: discord.gg/ChH726tbbF
─────────────────────────────
#ZXSpectrum #RetroComputing #Z80
