BYTE: Part 3 (Video cable & troubleshooting)

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The Clueless Engineer

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Published on August 4, 2022 12:50:37 PM ● Video Link: https://www.youtube.com/watch?v=IMv8ZlSP1cs

Duration: 15:53

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Apologies, video ran a bit longer than I had planned.

So, doesn't seem to be working exactly. I initially got some random video output, but then after a while nothing ... so perhaps one or more DRAM chips have failed?

I'm assuming my dodgy RGB+S cable is correct ... and I've connected it up to the RGBS input on the GBS8200 board.

Started troubleshooting with my Saleae Logic analyser. Checking the D0-D7 data lines on the UB880 show activity on all lines ... but after an initial burst of activity, it seems to be repeating the same stuff ... which, of course, would make sense if the machine had booted and was waiting for input.

However ... mashing the keyboard didn't seem to produce any noticeable change in the data ...

I was going to make a joystick DE-9-to-DIN converter cable so I could try a regular joystick but not much point if the computer isn't working.

So I think it'll be back to checking the RGB signal side of things, my dodgy cable, plus the ROM & DRAM.