Special thanks to PCBWay for sponsoring this video. https://www.pcbway.com/

Today on More Fun Fixing It, I tackle a Commodore 64 with the classic "black screen" fault. Armed with various diagnostic test cartridges, and the Classic Repair Toolbox software, I chase down a shorted 74LS257 multiplexer and various other faults. What should have been a quick logic chip replacement turns into a much longer journey thanks to a frustrating mistake on the bench. Watch to the end to see the C64 finally pass its diagnostics and to hear about the upcoming Retro Fest 2026 in Swindon.

Live stream where the first part of this repair started: https://youtu.be/vlOT9k2IUi8?t=2415

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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: https://www.patreon.com/c/morefunmakingit

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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: https://www.youtube.com/@MoreFunMakingIt

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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: https://discord.gg/ChH726tbbF

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