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RM650x, idling with 0% load but continues to build up temperature


pvc
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Hi,

 

I've purchased RM650x in April for my simple APU computer with the follow specs:

 

CPU : Intel i5-4590

MOBO: Asus H97-PRO

GPU : -------- (CPU integrated)

SSD : Samsung 850 EVO

 

As you can imagine there is not a lot of power draw here, however, even when I cold start the computer and leave it idle in login screen (debian buster) for 4 hours, it would continue to build up temperature until the PSU back plate is very toasty and the fan eventually kicks in. I have tested this twice and the source of the heat originates from the top right (when looking at the PSU back plate exhaust) where the RM650x logo is.

I've confirmed that the cpu is in reduced power state and is running at cool 30 C so there really is 0% power draw.

 

I just need confirmation that this is not standard behavior. I suspect it's not because I have a corsair 850W powering my gaming computer and a 1000W powering my server that's been online for 4 months with no problems.

 

Cheers

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Hi,

 

I've purchased RM650x in April for my simple APU computer with the follow specs:

 

CPU : Intel i5-4590

MOBO: Asus H97-PRO

GPU : -------- (CPU integrated)

SSD : Samsung 850 EVO

 

As you can imagine there is not a lot of power draw here, however, even when I cold start the computer and leave it idle in login screen (debian buster) for 4 hours, it would continue to build up temperature until the PSU back plate is very toasty and the fan eventually kicks in. I have tested this twice and the source of the heat originates from the top right (when looking at the PSU back plate exhaust) where the RM650x logo is.

I've confirmed that the cpu is in reduced power state and is running at cool 30 C so there really is 0% power draw.

 

I just need confirmation that this is not standard behavior. I suspect it's not because I have a corsair 850W powering my gaming computer and a 1000W powering my server that's been online for 4 months with no problems.

 

Cheers

 

It's normal.

 

Right where that "RM650x" logo is, is the bridge rectifier. It is constantly energized regardless of load. It keeping bus power on the primary side a steady voltage, even in standby.

 

In operation, that part is just going to get hotter and hotter. While it has a pretty chonky heatsink on it, without active cooling (the fan) the heatsink is eventually going to get saturated and the fan will need to turn on.

 

So, in your build that logo is "top right", so that would mean you're using that PSU with the fan pointing down. What case are you using? Can the PSU be mounted with the fan up?

 

I mention this because with the fan down, heat will rise into the PCB. With the fan up, the heat will rise away from the PSU's PCB and the fan shouldn't turn on as often.

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Thank you both for responding.

 

It's normal.

 

Right where that "RM650x" logo is, is the bridge rectifier. It is constantly energized regardless of load. It keeping bus power on the primary side a steady voltage, even in standby.

 

In operation, that part is just going to get hotter and hotter. While it has a pretty chonky heatsink on it, without active cooling (the fan) the heatsink is eventually going to get saturated and the fan will need to turn on.

 

So, in your build that logo is "top right", so that would mean you're using that PSU with the fan pointing down. What case are you using? Can the PSU be mounted with the fan up?

 

I mention this because with the fan down, heat will rise into the PCB. With the fan up, the heat will rise away from the PSU's PCB and the fan shouldn't turn on as often.

 

The case allows either direction but I have it facing down, I always do this because it seperates the air flow from the rest of the system (so it can draw cold air from the bottom instead of whatever is in the case) and to prevent build up of dust inside the psu which can be annoying to clean. I feel this is common given case designs today come with preinstalled psu shroud and also practically every case having bottom fan filters specifically for PSU.

 

I think your suggestion is great and is something I will test out, but something bugs me, I've also got a corsair RM1000i PSU running currently in another system, it's stone cold and been online for days. Obviously because of the price difference (the RMi part is around double the price) the more expensive part probably has a lot beefier heatsink, a different design etc.. , whatever it is, clearly a higher quality and the price reflects that. But my point is and here is the question, If I want to build a simple APU computer for work, something that won't be overclocked and doesn't really draw that much power overall compared to lets say a gaming system, which Corsair PSU best matches this type of workload while at the same time maintaining the high quality parts? Or is the answer just "get a laptop instead" ?

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Turn the PSU so the fan is pointing up. The PSU is rated to run at upwards of 50°C, so worrying about it intaking cold air is a non-issue. Furthermore, if the fan is not spinning, it's not taking in an air at all and only suffering under its own generation of heat which could be rising away from the PCB if the PSU was mounted with the fan pointing up.

 

The higher wattage RMx doesn't necessarily have a higher "quality" BD, per se. The BD used is scaled with the output capability of the PSU. So naturally, a higher wattage PSU at a lower load is going to run cooler than a smaller PSU.

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I've switched the PSU to now point fan up and it has made considerable difference, after 4 hours of idling the exhaust side is lukewarm to the touch instead of hot as it was before, the fan side is now receiving most of the heat so this is clearly a success.

 

Thanks for the explanation and directions. This solved it for me.

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Yes, I discovered this when I was making PC's that were intended to stand on carpets ( syou turn the PSU the right way up because an intake at the bottom of the case would be blocked ). In fact running the PSU upside down is not the best configuration even for smooth floors.
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