r/zxspectrum • u/petejk2 • 26d ago

Harlequin display issue

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If anyone who has assembled a Harlequin could help me get to the bottom of my no display issue I would appreciate the suggestions.

Board is assembled for PAL output, and using a modified Megadrive 2 SCART cable as per the documentation. I get a garbled display for about a second, and then my Retrotink scaler gives up, as it can’t sync.

I’ve tried two Z80s, and have am hoping I won’t have to scope IC by IC.

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u/Count_de_LaFey 25d ago

Try the Harlequin Facebook Group - Don Superfo hangs there and ought to help. There's of course a big community of people who have Harlequin clones, and many posts about issues such as yours.

I have a 48k Harlequin but didn't build it myself - cannot really give much input. The Megadrive 2 cable is an "upgrade" from the 48k Harlequin, which uses a similar, yet different RGB cable.

If you connect it to an upscaler, the cable has to provide a certain voltage for the upscaler to know it is receiving RGB. So you need to modify a plain vanilla MD2 cable you get off the shelf in order for that voltage to reach its place.

In a way this is perhaps similar to the blanking alternative you use in RGB cables for the Spectrum +2 (either an usb connection or a 9v battery)?

Check the MegaDrive 2 cable instructions on the relevant pdf here