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Oxxidation
Jul 22, 2007
Problem description: I recently changed out my EVGA 750 G1 power supply for a G2 when the fan started failing. Everything is wired up and the computer is functioning, but now the motherboard begins to emit a persistent electrical hiss/buss a few seconds after the computer powers on. The sound continues until shutdown. I've checked all the fans and the PSU itself and narrowed it down to the mobo - it sounds to be coming from somewhere around the CPU power supply socket plug, specifically.

This was my first time installing a PSU and I'll admit I was a little clumsy, but I made sure to keep myself grounded and touch the actual motherboard as little as possible. Is this just coil whine after the installation of the new power supply, or something more severe?

Attempted fixes: Checked all fans, powered on the PSU without the motherboard.

Recent changes: Aside from the new PSU and new cables, nothing.
--

Operating system: Windows 10.

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor
CPU Cooler: CRYORIG M9i 48.4 CFM CPU Cooler
Motherboard: ASRock Z170 Extreme4+ ATX LGA1151 Motherboard
Memory: G.Skill NT Series 16GB (2 x 8GB) DDR4-2400 Memory
Storage: Samsung 850 EVO-Series 1TB 2.5" Solid State Drive
Video Card: MSI GeForce GTX 980 Ti 6GB Video Card
Case: be quiet! Silent Base 800 (Black) ATX Mid Tower Case
Power Supply: EVGA SuperNOVA NEX 750W 80+ G2 Fully-Modular ATX Power Supply
Optical Drive: Asus DVD-E818AAT/BLK/B/GEN DVD/CD Drive

e: also, in case it's helpful, here are the voltages I took with CPUID under normal load:

Hardware monitor Nuvoton NCT6791
Voltage 0 0.59 Volts [0x4A] (CPU VCORE)
Voltage 1 1.70 Volts [0xD4] (VIN1)
Voltage 2 3.34 Volts [0xD1] (AVCC)
Voltage 3 3.33 Volts [0xD0] (3VCC)
Voltage 4 1.02 Volts [0x7F] (VIN4)
Voltage 5 1.02 Volts [0x7F] (VIN5)
Voltage 6 1.02 Volts [0x7F] (VIN6)
Voltage 7 0.00 Volts [0x0] (VIN7)
Voltage 8 0.59 Volts [0x4A] (VIN8)
Voltage 9 1.29 Volts [0xA1] (VIN9)
Voltage 10 1.02 Volts [0x7F] (VIN10)
Voltage 11 1.70 Volts [0xD4] (VIN11)
Voltage 12 1.02 Volts [0x7F] (VIN12)
Voltage 13 1.22 Volts [0x99] (VIN13)

Oxxidation fucked around with this message at 23:56 on Feb 18, 2017

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Actuarial Fables
Jul 29, 2014

Taco Defender
Are you sure you have a motherboard and not a snake? Please don't power up snakes.

Make sure there's no foreign objects in the CPU power plug and ensure that all connections are fully inserted. Make sure to use the cables that came with the G2 and none of the G1's - although they're EVGA branded, the G1 and G2 are made by different manufacturers.

If you have your old PSU still, try swapping back to see if the issue persists.

e. While you're in there checking it out, make sure your motherboard has all its mounting screws in. They ground the motherboard to the case and may potentially cause electrical funkiness if not installed. They should be snug, but not tight.

Actuarial Fables fucked around with this message at 03:18 on Feb 20, 2017

Oxxidation
Jul 22, 2007
Re-checked my connections, all cords were snakes. Was bit repeatedly by snakes. Will return PSU and leave two-star review on Amazon (one extra star because snakes were non-venomous).

Joking aside, I just took another look around the case, saw everything looking OK, then did another pass at Google and decided to turn off C-States in the BIOS. That seems to have eliminated the noise - guess it was coil whine from the CPU. Will there be any long-term consequences for this, or do you think I'm good?

Actuarial Fables
Jul 29, 2014

Taco Defender
From where you've pin-pointed the sound, it seems like it's the VRM on your motherboard that's making the noise (but I can't say for sure). If the CPU itself was making noise then you'd probably be having much bigger problems.

Running with C-States disabled won't harm your components, but it will increase your power bill somewhat as your CPU will be at full voltage all the time. Since it's a desktop, battery life and cooling impacts aren't that much of a concern.

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