PSU trips when CPU is attached

[Andrew Wright]

Hi,

I have a problem with my HTPC that I'm hoping someone can help with. The equipment is listed below for reference;

Streacom FC8 Evo Fanless Case
Pico 160w PSU
AMD A6-5400k CPU
2 x 2GB Kingston memory
Kingston KC300 SSD
ASRock FM2A75M-ITX board

The HTPC was failing to boot whereby the PSU trips immediately after powering on. I did the usual testing of using a known working power supply to rule this out and the issue remained (this power supply was used for the following testing). I then removed each component (with the exception of the CPU) individually and tested each time with the problem remaining. I removed the motherboard from the case and tested with all components disconnected (again, excluding the CPU) and the problem remained. I removed the CPU from the motherboard and the PSU powered on and remained on. I confirmed this by reattaching the CPU and testing then detaching and testing again.

I am now in a position where when the CPU is attached the PSU trips, however, functions correctly when the CPU is removed from the motherboard.

Has anyone seen this before? If so, is it likely to be a problem with the motherboard or the CPU itself? The pins on the CPU are not damaged and it seats correctly. I ask as without an alternative FM2 motherboard or CPU I cannot confirm which component is at fault.

Thanks.

 

[jb6684]

What was the "other PSU" you tried? Systems typically draw 80 to 200 watts that supply sounds Awefully small. Try it with a 350watt supply.....

 

[clutchc]

It's not surprising that removing the CPU stops the fault. When there's no processor in the MB, the system is essentially off. What is the nameplate rating on the 160W PSU? That little thing may be too small for the load the system presents at start up.

 

[Andrew Wright]

Thanks for the reply.

The power supply that was in use previously was only 160w and functioned fine for upwards of 6 months without issue - when in use the HTPC simply streams over my home network. Whilst troubleshooting I have been using a functional 350w PSU from a desktop PC so I'm inclined to suggest it's not the PSU.

 

[Andrew Wright]

Clutchc, as no other components were attached when the PSU worked would you think that would point to a problem with the CPU as it would indicate the motherboard alone is not causing it to trip? I ask as, from my understanding, it could still point to a problem with the motherboard that is only present when the CPU is attached.

 

[clutchc]

Clutchc, as no other components were attached when the PSU worked would you think that would point to a problem with the CPU as it would indicate the motherboard alone is not causing it to trip? I ask as, from my understanding, it could still point to a problem with the motherboard that is only present when the CPU is attached.

Since the system worked before on a 160W PSU, we can assume that is sufficient size. In that case it sounds like there is definetly a problem. The APU would be the last thing I would suspect. The MB would be the first thing I would suspect, however. Have all these components been in service together before?

 

[Andrew Wright]

They have been yes. They were all purchased and installed at the same time and haven't shown any indicative symptoms of potential problems previously.

 

[clutchc]

They have been yes. They were all purchased and installed at the same time and haven't shown any indicative symptoms of potential problems previously.

I believe that is one of those cases that come with a do-it-yourself CPU cooler in which you assemble heat pipes and radiators to dissipate CPU heat, and it comes with a laptop style external PSU, correct? Have you been monitoring the CPU temps to see if it was staying cool? I am wondering if the CPU could indeed be the culprit in this case due to over heating.

 

[Andrew Wright]

That's a very valid point and one worth considering. You are right about the case.

For the first month I monitored the temperatures and they weren't cause for concern. Due to the nature of the case, it dissipates heat through the heat pipes and via a heat sink and so until this heat dissipates the CPU runs hotter than it does once the heat is being transferred, yet still within the operating temperatures. It eventually stabilises at a comfortable temperature.

 

[clutchc]

I hesitate to blame the APU because they so rarely fail if not abused by over heating/over volting/over clocking. My first suspicion is always the MB because it contains the majority of the components that can fail. But in your case, I'm not sure. Trouble shooting from afar is always difficult. And it's not like you can just easily find someone that has the same type processor or MB to swap parts with.

Was this a kit; did it come with an Asrock MB designed for the case? I did a bit of a search to familiarize myself with the Streacom FC8 Evo Fanless Chassis. It looks like an interesting HTPC build. Perfect for an entertainment area where a quiet PC is essential.

 

[clutchc]

How were you able to use a std ATX PSU for testing? Do the MB headers all match up with std connectors?

 

[Andrew Wright]

It wasn't a kit, no. I sourced the components individually. Streacom have documentation on their web site detailing the requirements of a motherboard.

They also suggest a number, 3 I think, of motherboards that can be used with this case based on size and positioning of parts to allow space for the cooling pipes. These are 1150 socket boards which would allow the use of a low TDP chip. The A6 CPU also has a low TDP of 65w, equal to an equivalent Intel CPU that could be used with one of the recommended motherboards and as recommended by Streacom.

The motherboard is a standard 24 pin power plug, as is the PSU I've used whilst troubleshooting.

 

[Andrew Wright]

To update, a replacement motherboard has now been tried and the issue remains. A replacement CPU will be tried tomorrow.

 

[clutchc]

Can that tiny Pico PSU actually handle a 65W processor plus MB components, RAM, etc? Seems awfully tiny. I can't find any good specs on it. What is its +12V output rated at... amps and watts?

 

[Andrew Wright]

http://www.mini-box.com/picoPSU-160-XT

It's only power the AMD cpu, 2 sticks of RAM, a HDMI output and a network port. When testing yesterday, I again used the known working 350w ATX PSU that I know to working fine.

As the only common component here is the CPU, as unlikely as it seems, must be the root of the issue. Once I have a replacement CPU I will update.

 

[Andrew Wright]

So a brand new CPU has now been tried also and the issue still remains. For the purposes of testing and to rule out potential issues with the power switch itself I have attached a CPU fan as an indicator as to when the computer is powering on successfully (where it is being tested it cannot be connected to a monitor) and attempted to power on using jumper tongs.