Question Strange Problem with System Power LED and Motherboard Leads

Apr 4, 2022
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Hello. I hope i've posted this correctly as it's my first post. This pertains to the system power LED light on the CASE.

I have a steel legend b450m Motherboard and a Thermaltake v200 case. Everything on my PC is working and my PSU is delivering proper power to all components. My problem is, when the computer is off but the PSU is on, My system power LED is on. BUT, when i turn the computer on, the system power LED turns off. It's basically reversed.

I can't find another person with this problem anywhere, and I've tried about 20 solutions. I have the PLED in the correct lead, but the light is on when the system is powered off. So there can be no soldering problems at the case, no power problems at the psu, something else is wrong here. Please let me know if you need any additional information.

Thanks very much in advance. Furthermore, I'll add that this systems power LED light worked perfectly before, with the same motherboard. I replaced the PSU and when plugging things back in this problem started. PSU is Corsair CV550. The PSU reaches gaming loads and modulates varying amounts of power to the computer so i doubt it's the new PSU. Finally, I'm using a simple PLED+ and one PLED-. Does this case come with three PLED connections? My mobo manual shows two connections for PLED on the system control header, and 3 connections for something also called "PLED" right next to it. Is it possible there is a third power LED connector I can't find? I have restored original UEFI settings in bios and that didn't help either. Something really messed up is going on here.
CPU: Ryzen 2600
Motherboard: Asrock Steel Legend b450m
RAM: 16 GB (2x8) Corsair Vengeance 2133 mhz (xmp to 3000 mhz)
SSD/HDD: Boot Drive Samsung 980 1 tb + Samsung 850 Evo 500 gb + WD Blue 2 TB
GPU: MSI Ventus 1660 TI
PSU: Corsair CV550
Chassis: Thermaltake v200 RGB glass Edition
OS: Windows 10 version 20H2 (OS build 19042.1526)
 
Last edited:

Lutfij

Titan
Moderator
Welcome to the forums, newcomer!

For your system specs, might want to list them like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:

Breadboard the system innards and see if you get any signs of life/POST from the above build.
 
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Paperdoc

Polypheme
Ambassador
My best guess is that you have inadvertently reversed the way the two wires from the front power LED indicator are plugged in at the mobo System Panel header - mobo manual p. 28, upper left two pins. Try just swapping those two wires at the mobo header. This will NOT damage the LED - connecting backwards can merely cause the LED not to light, or to do the odd things you describe.
 
Apr 4, 2022
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This is the best answer i've gotten (thread is cross posted), however... it doesn't work. Something is simply wrong at the pins. It simply doesn't light when i reverse them. Without different psu/mobo to test with ... i'm at an impass
 

Paperdoc

Polypheme
Ambassador
If the LED simply does nothing when you reverse its connections, then that is the wrong way, and you DO have it plugged in correctly there. The LED itself can't really do this, so it must be odd signals being sent out by the mobo from those pins.
 
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Paperdoc

Polypheme
Ambassador
It occurred to me later, you could test my statement that the LED is not the problem source, if you wish. The front panel LED indicating HDD activity is exactly the same device. So you could temporarily swap the leads for the power LED and the HDD LED at the mobo Front Panel header, and observe. If the odd behaviour stays with the header pins, and does not depends on which LED is connected where, you know.
 
Apr 4, 2022
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I have. when i swap the PLED into the HDDLED pins, what happens is the PLED begins to blink with HDD activity. Basically, the leads/headers are just fine. It's something wrong with the PLED pins. Also, when i swap the HDDLED into the PLED pins, it does the same thing but with the HDD led. It's off when on, on when off.
 

Paperdoc

Polypheme
Ambassador
Right, that's what I expected. That proves the issue is the signals being fed out of the PLED pins of the Front Panel Header. MAYBE ASRock Tech Support can tell you how they are supposed to indicate things. I do not think this odd behaviour results from some power settings in Windows, but I may be wrong there.
 

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