pooter powersupply

[HELModels]

I got to write this quick as she's getting ready to meltdown. The fan on my computer power supply cuts out after only a few minutes post boot. I tried an aircompressor to blow out the dirt and I've tried nudging it with a plastic stick, but nothing. Is it the fan? Is it something fixable? Why would the fan run for a minute or 2 and then stop and not restart? let it cool down and boot and the same thing - fan runs then stops.

[Andrew0820]

This a bit OT, but here are some options.

(1) If the fan bearings are bad, usually the fans will not start, but if they do, they tend to continue to run. If it spins freely when flipped with a pencil or stick, then bearings can normally be ruled out.

(2) Some power supplies have an internal thermal fan speed controller to hold fan noise down. These controllers many times will start the fan at full speed, then slow it down. The controller may be going bad. You can identify the controller as a small daughterboard, usually screwed to one of the heatsinks, with input coming off the PS PCB, a thermistor held to the heatsink with a small bracket (thermistors look like capacitors and are most always green or brown) and output going to the fan. You can cut this controller out of the circuit and wire the fan directly to a 12v source.

(3) Some PS have sensor wires running to a processor heat sensor on the motherboard. On occasion, I found that unplugging this sensor will keep the fan running at full speed.

(4) Your fan may be faulty -- they are cheap and easily replaced. Fan sizes are determined by the outside dimension of the fan housing -- usually 80 or 90 mm for most supplies.

andrew

[HELModels]

Thanks for such a thorough answer, Andrew.

It is not the bearings as it spins nicely, but it must be something as you described. I found a deal on a gamer's 500 W PS and that should solve it.
As for this being OT, I disagree as the hurtin powersupply might be fixable enough for battery charging. How do I avoid shock therapy when I tear it open?

Anyone?

[Andrew0820]

How do I avoid shock therapy when I tear it open?



Let it sit for 24 hours -- most of the caps will bleed down in a few minutes anyway.

[Pete P]

I had the same problem with an old Flex-ATX PS rated 90W :-P

I simply took the fan out, and used a regular fan (same size) with wires coming out of the PS and plugged back into it.... Lost thermo-controlled fan though, but always on isn't a problem. Also, try and match amp-rating... You get similar airflow.

Wear leather gloves and use plastic tools, if you have the option. You may zap-a-cap but you wont zap yourself :-)

[Malc C]

You may zap-a-cap but you wont zap yourself :-)

Pete,

takes me back to my apprentice days... we came across a couple of old capacitors that were several thousands of uF (they were about the size of a coke / red bull can), and someone (I'm not mentioning who :rolleyes: ) thought it would be a good idea to short one out using a large screwdriver.... kept seeing the "black spot" before my eyes caused by the arc for hours afterwards :) - it almost welded the screwdriver to the terminals... :)

[Pete P]

I have a couple of those, old server backups :-) Ever repeated said operation with a car battery :-D?

[HELModels]

O.K. so to get a PS suitable for charging batteries, all it takes is bypassing the multispeed thermosensor numbnut circuit after waiting 24 hours for the jumbo sized capacitors to leak their leathal charge. Believe me, I'm in no hurry to short a giant capacitor.
I seen it done once and it wuz excitin. With the mothaboard and all my peripherals removed, there is plenty of room for an ammo box and a lipo charger.

Thanks for the help everyone!!.

[Malc C]

I have a couple of those, old server backups :-) Ever repeated said operation with a car battery :-D?

Nope.. but I have seen an exploded car battery :eek:

I bought an Vauxhall Senetor 3.0, what a lemon... Jumped in one morning, turned the ignition... BANG ! - what I though was steam coming from under the bonnet turned out to be acid ! - the battery resembled an un-wrapped slice of bread, all the plates were soreading apart !!

The car was the 5th electrical issue we had with the car in as many days as as the car was still under warranty and eneded up going back this time for a full cash refund !

Getting back on topic (slightly ;) ) I wonder what current was drawn from the battery to cause it to explode like that (half the plastic casing had completely gone)

[Andrew0820]

O.K. so to get a PS suitable for charging batteries, all it takes is bypassing the multispeed thermosensor numbnut circuit after waiting 24 hours for the jumbo sized capacitors to leak their leathal charge.

I takes a little more work to get your supply functioning as a standalone PS. Incidentally, 15 minutes will clear most of the caps in your PS. Here are some converstion instructions (http://web2.murraystate.edu/andy.batts/ps/powersupply.htm).

[HELModels]

Andrew, yup, I took a look at that and will heed.

[HELModels]

Wow, just installed the ULTRA 500W X-connect powersupply and that is a really good one. Atleast compared to the one I've been talking about repairing. I hope the old ps is even good enough for charging lipos. The ULTRA runs quiet and cool while the futurepowerfailure 300W is hot and lousy after only a few minutes. Even my keyboard works better now, seriously.