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#11
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Can I make my power supply fan turn faster?
Steve Hough wrote:
Rene Lamontagne was thinking very hard : WARNING !!!!!! IF you open up the PSU be warned that the large Caps can store a very dangerous Voltage. If your not familiar with This stuff, leave it alone and buy a new PSU. Rene Indeed. As the o/p has already managed to squirt the wrong oil into it. I'm surprised so many others here advocated opening the thing up. And if he waas familiar with this stuff, I doubt he would have uses WD40 in the first place. If the fan is soldered to the PCB, I would not attempt to replace the fan. If the fan uses a connector, you may be able to unplug the connector. The most dangerous part, is trying to use tools to torque the connector to get it loose. If a tool slips off, it could hit a high voltage item. In any case, this is one reason the fan connector is on the periphery of the PCB and not in the middle of it. You don't have to get "up close and personal" with the main cap, to change out a fan. ******* There is as much danger in making the main caps "safe", as there is in working around the main caps. To see which caps are dangerous, there is a sample schematic here. Modern PSUs don't use the same architecture (they do double forward conversion), but in terms of safety issues, this is a good primer. http://www.pavouk.org/hw/en_atxps.html Capacitor C5 and C6 are larger devices (tin cans), which are charged to 300VDC or higher. If you work out 1/2*C*V^2 , the number of joules involved is similar to that of a microwave oven cap. *Do not* stick a screwdriver across the two wire ends of a C5 or C6 cap, as the noise is loud enough you could lose an eardrum. 1/2 * 0.000470 * 300 * 300 = 21 Joules Resistor R2 and R3 are bleeder resistors. They're in the circuit, to drain C5 and C6 after about an 8 minute delay. That's a safety feature. If we didn't need safety, R2 and R3 would not even be in the circuit. They only have one reason for being there. (I count waiting five time constants as being long enough.) But technicians working on a circuit like this, assume R2 and R3 are defective and have gone open circuit. And they further assume C5 and C6 are fully charged (it's a bit like defusing a bomb). If a technician wanted to solder something on the bottom of the PCB of the power supply, they would use an *external* bleeder resistor to quietly (and slowly) discharge C5 and C6. There is always the danger of getting a shock, while making the caps safe! (If you make a bleeder, you make yourself some Plexiglas handles to position it, and so on.) If I see that the fan connector is "off to the side" and I can work on the low voltage fan connector without getting near C5 and C6, I'll do that. If the fan is soldered to the PCB, I would probably decline to work on the project and just buy a new PSU. I only got one decent shock in all my time doing electronics. I got my "teaching" shock as a kid, working with an ignition coil. One minute I was at the workbench, the next minute I was getting myself off the floor, and I apparently had jumped backwards and hit the floor when the shock got me. I'd laid something on top of some wires, and didn't see a HV wire underneath something else, and that's how my little experiment "got me" :-( I've worked on high voltage since then, with no other incidents to report. For example, I have a flyback circuit with a tripler on the output, for HV work, and that circuit has never managed to get me. It would likely burn as much as shock. But the reason I've not had a shock since, is the first lesson was *the best* :-) You couldn't ask for a better lesson. I presume I passed out for a moment, but I'm not really sure. Because I don't know exactly how I hit the floor. Some of my other experiments as a kid, did more damage. That one wasn't the worst. A good lesson is one you learn without bleeding or a concussion. Paul |
#12
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Can I make my power supply fan turn faster?
Paul has brought this to us :
Steve Hough wrote: Rene Lamontagne was thinking very hard : WARNING !!!!!! IF you open up the PSU be warned that the large Caps can store a very dangerous Voltage. If your not familiar with This stuff, leave it alone and buy a new PSU. Rene Indeed. As the o/p has already managed to squirt the wrong oil into it. I'm surprised so many others here advocated opening the thing up. And if he waas familiar with this stuff, I doubt he would have uses WD40 in the first place. If the fan is soldered to the PCB, I would not attempt to replace the fan. While you are patently very knowledgeable on electronics, is it not possible sometimes to answer people with just one sentence. When it comes to the o/p, I would just presume that someone who just squirts the wrong oil in and hopes, is too stupid to be openeing up a PSU. |
#13
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Can I make my power supply fan turn faster?
On Tue, 10 Jul 2018 12:26:56 +0100, Steve Hough
wrote: o/p, I would just presume that someone who just squirts the wrong oil in and hopes, is too stupid to be openeing up a PSU. No one taught me how to work on Killer Amps - 500V on vacuum tube plates and some relatively huge capacitors. Or fabricate from a 600 amp 220V welder. Enough to where I can fix the more obvious mechanical issues, taking a plastic prod to a live amp to find cold solder joints. Rebias fresh tubes, or amazing things like keep patched vehicles running out of junkyard parts. Yes, and even steal fans from an otherwise dead PSU. At one point I'd even have made the classical disconnection with electrical contacts and WD40. There's just one thing better than stupid and that's scared: Not being mindful of not being the foremost expert when approaching hazardous work is stupid. But that applies to anything with a will. I watched a guy next door climb to trim a tree, bright and early one morning, singing like a bird at the top of his voice. He got up there, touched a nearby power wire and fell on the chain-link fence below. He obviously didn't have a will to stay put. So they carted him off in a helicopter that landed in the adjacent intersection. A grain of salt may not help while driving and losing brake lines, the steering box dis-coupling at the steering column. Nor will a slew of uselessly stinky reviewers scratching their collective asses on YouTube instructional videos. But I still watch, if I need the help over leaving it. A "professional FWIW" viewpoint. It's where leaving it -- on the second time up -- is a given that there's definitely some aptitude that wasn't before. - Appraisals: $75 an hour. Correct Appraisals: $150 an hour. Stupid Looks: Still free if you act now. |
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