Happy Little Diodes is back on the bench to solve a stubborn Raemixx500 Amiga glitch that appeared after completing an Amiga 500 Plus clone. In this video, the host switches from builder to troubleshooter, methodically tracking down the cause of a strange graphical fault.
The Raemixx500, an open-hardware Amiga 500 replica, powered up successfully after hours of soldering. Yet, the joy faded when smeared pixels and overlapping scan lines filled the screen. Determined to fix it, the creator began a careful investigation. Testing started with the Denise chip, the heart of the video output. Switching to composite video confirmed the same distortion, meaning the issue started before the analog stage.
Next came the digital side. The buffer chips were swapped, but the glitch stayed. That pointed toward the Fat Agnes chip, which controls memory access and timing for video data. Since replacement chips are expensive, the creator turned to the Amiga Diagnostic ROM to confirm the theory.
After programming a large EPROM and running the diagnostics, memory and ROM checks passed. However, the scrolling test failed completely, filling the screen with garbage. That test uses the Blitter inside Fat Agnes, confirming it was the culprit. The only solution left was to replace the chip.
With a new Fat Agnes installed, the Raemixx500 Amiga glitch disappeared. The screen displayed perfectly, proving the fix successful. The repair increased the total build cost to about £636, but the satisfaction of a working system made it worthwhile.
The next episode will cover assembling the case, keyboard setup, and peripherals. Until then, this repair story captures the patience, logic, and dedication behind restoring vintage hardware.
