So, this is with the composite cable from the ZX Spectrum 48k into the gcompsw input and another composite cable from the output of the gcompsw and into the back of my PVM.
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If I plug the ZX directly into my PVM with either composite cable, bypassing the gcompsw:
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As for the LED light on the gcompsw, it never blinked when turning on the ZX, neither does it blink while it's on. It says solid-lit whether composite is plugged in, on, etc.
If it's a power issue for the gcompsw, then surely I would get issues with component but it works perfectly fine as demonstrated with my PS2 here (and it will also output to my FM simultaneously)
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Any thoughts? Thanks for your time!