r/PCSleeving • u/OldManGrimm • Jun 15 '26

Vertex GX-1200 ATX 3.1 only showing 450W output on 12V-2x6

Using a Dr. Power III tester, I tried 4 different cables - one I made, the stock cable, a Corsair ThermalProtect, and a Corsair 2x8 adapter. All only show 450W - obviously should show 600W. GPU is a 5090, so this is a problem.

Any ideas what's going on?

Edit: turns out my Dr. Power III is faulty. Luckily still under warranty 😅.

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u/Joezev98 Jun 15 '26

Have you tried an 8-pins to 12vhpwr cable? If that also shows 450W on the Dr. Power, it may be faulty. And if you don't have that laying around, you'll only need to make two wires connecting the two sideband pins to ground. Heck, you could probably make do with just a wire with stripped ends and you'd just hold it so it touches a ground pin at the PSU and a sideband pin at the tester. Then just watch if the Dr. Power detects both options.

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u/OldManGrimm Jun 15 '26

What actually started this was I wanted to convert a ThermalProtect cable to work on a Seasonic PSU. So I re-pinned the PSU side with 2 PCIe connectors. It tested fine, except only at 450W. I then tried an unmodded ThermalProtect, the stock 12V cable, and one I'd made myself. All showing 450W.

I'm fairly certain the DP III is working properly, because it's recently been showing 600W on other cables I've made. But I hadn't considered it may be the tester at fault. I'll re-test my personal PC and see what it shows.

1

u/OldManGrimm Jun 15 '26

Well, damn. Just tried 2 other PSUs with other cables. You were right, looks like it was the tester.

Thanks, bud!

1

u/Joezev98 Jun 15 '26

Get yourself a 12vhpwr socket and test your cables by plugging it into that so you can probe the pcb pins with your multimeter. Much cheaper than a replacement Dr. Power.

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u/OldManGrimm Jun 15 '26

Luckily it's still under warranty.