Re: Help OT: HP DC7100 SFF Power Supply

info@xxxxxxxxxxxxxxxxxxxxx wrote:
I have received back the above unit with remarks that it switches off
for no reason. The customer says there is no pattern to this and when
it occurs there is a total power loss and that the unit will operate
either minutes or hours before this happens. This sounds very odd to
me - have never encountered this type of problem before.

Any help or advice will be useful.

Regards

Kailash

Replies to cdtech@xxxxxxxxx please.


Hi,

Put it on a dummy 25%, 50% and 75% load and see if it still fails intermittently. If so, then it does have a fault and not something external.

Then see if you can trigger the problem by tapping it gently against the workbench, whilst running. If that triggers a failure, then it is a dry joint/hairline track break or similar.

The see if you can trigger the problem by temperature, by directing the air from a hair drier into it. If so, then see if you can pin down which component, probably a big capacitor, which is causing the problem. Look for ones near something hot (eg the recovery diode) as it may have dried out and its impdedance gone out of spec.

There is another interesting little problem that can arise. The over-voltage sense on one of the output rails may be tripping. So look at the voltages on the rails. This can often be brought on by *reducing* the load on the supply - eg fitting a lower consumption hard disk/optical drive, or switching to a power-saving regime where things are powered down when idle. The easiest solution is to disable power saving and increase the load and see if it then is reliable.

HTH
Sue
.

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