Minor problem here - my pc power sullpy died at 18 months old.

I was going to hand this in, because I only have the use of one hand. But I noticed that the cooling fan doesn't run. From my pc fixing days in the last millenium, all the cooling fans were mains powered, weren't they? Is that still the case?

I bought a pre-built PC, and the power supply and it's dozens of very long leads are all wound into and knotted through the box. So it's going to be torture to remove.

Is there any common faults I can check for on the mains end of the PSU but internal to the caged bit of the PC? There must only be half a dozen components there. I was a hardware techie but it's very different now. I can still talk a good job, but you need 2 hands to even solder!

The case fans are typically 12VDC and more commonly now days plugged into the motherboard. The 12VDC is also used to power 3.5 inch hard drive motors.

Hi,

The PSU fans are connected internally to the unit. If that fan is out then it's probably certain that the PSU could be faulted or in need of replacement. I know how hard it is to be limited due to manual problem with one's hands. I've learned several techniques for the problem with one hand to do things. Thankfully I have my full dexterity back. It's a bear to do things one handed, even if your ambidexterity minded. Try putting on a bracelet on your off hand. My wife always helped me with that. Now I use tape to hold the bracelet in place and use my opposite thumb and forefinger to open the clip. Sounds silly but it does work.

I do have magnetized tools to aid in screw or nut holding. Slotted screw is not a problem when you have a screw gripper driver/starter screw driver. If you have a hand injury it can be a pain to do normal things. Sometimes you need to think out how to handle the situation.

I hope your problem is just the need of a PSU replacement.
Hope this helps.

If you mean PSU fan doesn't run, that may be normal until some heat builds up in the PSU. It's one way to "save the planet" by using less electricity. I think it's stupid, because a running fan indicates the PSU isn't stone dead, the closest thing to smarts most PSUs have.

Thanks. I've learned several one handed techniques as well. but I've other issues as well and passed down my rather extensive toolkit. I was repairing industrial electronics and down to component level on PCBs back when that was possible. I used also repair my family's two and 4 wheel transport.

Now it seems nobody in this country has a soldering iron.

Agreed. But if the mains powered fan is out, that's a mains fault, which doesn't really touch all the low voltage stuff. So what I was hoping for was a hint about pcb fuses or whatever, because if power is getting to the bridge rectifier, my dud power supply is going in the bin. But I'd fix a dry joint, pcb fuse or broken switch getting there, and save myself effort.

I'm realising everyone throws power supplies out without thinking in line with Rule #2 of maintenance: "If it ain't worth it, don't fix it!" I don'tmind the money, but I do mind the pain of replacing it. That's what tempted me to look. My worst nightmare would be buying a psu, fitting it, and still having a problem .

There probably is a soldered fuse.

Any fan I have seen in a PSU in the last 20 years or so has been a standard 12V fan of some sort, much the same as a typical case fan, often using the same connector, either connected to the PSU PCB internally, or to a connector on the PC motherboard via the wiring loom.

Most fairly modern motherboards have some manner of surface mount indicator LED. Just connect up with the case open and see if that lights. If it doesn't and there's no response or you're not sure if that LED is present, you could just unplug ATX power connector and try shorting pin #14 (green wire) to any ground (black wire) and see if the PSU powers up.

Short answer: No.

There's a 90% chance the fan is powered directly from the 12V rail, as mickaelk pointed out. If it's a mid- to high-end PSU there might be a temperature-controlled regulator involved as well. Edit: There should be a sticker at the center of the fan showing the operating voltage and current draw. It may be possible to read it through the grill.

Most ATX PSUs fail due to bad capacitors. Yes, decades after the "capacitor plague," this is still a common issue. On the low voltage side, that is; the bulk capacitors rarely fail.

Do you have a multimeter? The presence or absence of 5V standby power could potentially tell you a lot about what's wrong.

If there's no standby power, you either have a non-working standby circuit (very common) which in turn will prevent the entire PSU from powering up, or there's been a catastrophic failure on the HV side (which will probably have blown the internal fuse).

If you have standby power and you still can't start the PSU, bad capacitors on the low-voltage side is the most likely cause.

In either case, some soldering will be required to get the unit up and running again. I'm very sorry to hear that you're not able to use both arms, because it sounds like you'd otherwise be more than capable of performing the necessary repairs.

Thanks for the detailed reply. While in business, I would never have taken a Computer PSU to fix, because anything with low replacement cost didn't get looked at. For me this psu has high replacement cost, purely because I'v only one hand and my son is a musician. We do the odd job together with my brain & his hands. He can do stuff, he just doesn't want to.

With the PSU only 18 Months old. I'm not thinking of capacitors first. What you're saying makes me feel I'd have to go playing with the PSU. In which case, I'll hand in the box and let some young nerd thread the new one, and jangle his nerves & patience. I'd need a quick fix or nothing.

Hi,

You would have to open the PSU to find a potential inline fuse. Most you would have to check the line side of the fuse and the output side to see if the fuse is open. Hopefully you could ID the current requirement for that inline fuse.

As to thermal control PSU fans, most newer designs do have a thermal sensor circuit to switch the fan on/off PWM relative to the temp air flow of the PSU. I've seen four pin IC I2C chips for PWM fan speed and for temp control but yet to see a PSU manufactures circuit diagram or from someone that traced out the circuit. It's doable using several packaged I2C modules for PWM and temperature control.

My time is worth a lot to me and would not get hourly charges to cover the cost of troubleshooting internally a PSU circuit so a shot gun of the PSU would be cheaper for the client and myself.

At one time when PSU were not really disposable but would need capacitor replacements but most today are just shotgunned because of the replacement cost factor vs labor charges.

I'm sure you are aware of the one hand rule when circuit checking levels to prevent reactionary results when a ground situation occurs when probing.

I remember one incident when a tech was probing a HV circuit and a personal discharge caused a physical reaction when the tech inadvertently grounded himself and physical reaction caused a serious injury cutting his hand badly.

I would tell my students to be very cautious when troubleshooting electronics/electrical circuits. Better safe than sorry!

Hope this helps.

On the power supply: It's sorted. I'll buy, my son will fit. He'll find out how hard it is, but it's too late then

I remember the One Hand Rule well. I cut my teeth on valve TVs with 21-25KV on the tube, and about a third of that on the L.O.P.T. Burns were common. Another trick was to touch something you thought was not live with the back of your hand. Your instinctive reaction was to close the fingers. So you'd disconnect yourself when you discovered it was live.

The lethal things were RF generators. They had 5-30KV or even more at over one amp of current. At 10K ohms body resistance, you could pass half an amp, and consume 2.5KW in the process! They were usually on concrete floors; So you'd be working there too.

Hi,

I remember repairing early TV's and having to discharge the anode using a discharge probe. Man even with the probe it can be unsettling for a first timer.

I remember my early days working on electronics/computers at a local newspaper. I would have to discharge the static generators for the press to make repairs. I have been hit a few times by residual charge and that was not comfortable. Worse than an electro-static discharge.

My uncle was a trickster and would place a model T coil and switch it on when we approached his car. Boy would we get hit since we were bare footed. Other times he would put a discharge point(spark plug) at his exhaust and rich the gas a little and would that ever back fire shooting out a big flame.

Sorry for the Off topic but memories do come back from long ago. The climate change people would go nuts for anyone doing such today.

Welcome the OT - I was being OT myself!

We never had tools for discharging tubes, but we did have wooden flooring,often very cheaply done, over concrete. I'd usually risk a shock with two long plastic handled screwdrivers with the long metal bits in contact. I was pretty immune to shocks. Otherwise, wrap a wire around the business end of a long screwdriver, and earth the other end of the wire. You would have to remember that the wire's insulation was useless.

Woe to anyone who let a finger reach over the end of the plastic handle, though. But lightning strikes heal quicker than cuts, and they're sterile.