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#1
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PSU type compatibility?
I know of 5 PC: PSU types, based on the connectors:-
1. with 2 side-by-side, single row sockets that plugged to the PC single row of pins. 2. with 2-rows of 10 sockets to 20-pins of PC. 3. above "2" plus 2x2=4-way socket yellow-black wired. 4. above "3" plus extra 2x2=4-way socket which can slot onto 2x10=20-way socket to fit 24-pins of PC. 5. as above "4", but with one-piece 2x12=24-way socket . I seem to remember that I once ran a PC without the yellow-black 2x2=4-way socket feeding the 4 pins. Is that possible? And that I ran a 24-pin MOBO with a 20-pin PSU? Clearly, many of the wires supply in parallel, to cater for the increased current, as the PC evolved, and the PCB tracks couldn't be increased in width. I bought a spare MOBO, which can handle SATA & IDE, and which you can't buy new here. After testing it with my PSU of my normal SATA & IDE MOBO, I wanted to connect it as a standby. So I plugged a "type 3 above" PSU, which had been running an old IDE only MOBO. The CPU-fan didn't run although I "reset" the same pins as for the successful test. After a minute, an electolytic capacitor exploded. Later someone with a fancy PSU tester said the PSU was dud. What happened? The 20-sockets PSU had been running the old IDE-only MOBO, but the 2x2=4-way socket yellow-black hadn't been used. No MOBO pins. If the 2x2=4-way yellow-black supply had been drastically faulty, the old IDE-only MOBO, would not have detected the problem. Not connected. I guess? |
#3
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PSU type compatibility?
In article , Paul wrote:
wrote: I know of 5 PC: PSU types, based on the connectors:- 1. with 2 side-by-side, single row sockets that plugged to the PC single row of pins. 2. with 2-rows of 10 sockets to 20-pins of PC. 3. above "2" plus 2x2=4-way socket yellow-black wired. 4. above "3" plus extra 2x2=4-way socket which can slot onto 2x10=20-way socket to fit 24-pins of PC. 5. as above "4", but with one-piece 2x12=24-way socket . I seem to remember that I once ran a PC without the yellow-black 2x2=4-way socket feeding the 4 pins. Is that possible? And that I ran a 24-pin MOBO with a 20-pin PSU? Clearly, many of the wires supply in parallel, to cater for the increased current, as the PC evolved, and the PCB tracks couldn't be increased in width. I bought a spare MOBO, which can handle SATA & IDE, and which you can't buy new here. After testing it with my PSU of my normal SATA & IDE MOBO, I wanted to connect it as a standby. So I plugged a "type 3 above" PSU, which had been running an old IDE only MOBO. The CPU-fan didn't run although I "reset" the same pins as for the successful test. After a minute, an electolytic capacitor exploded. Later someone with a fancy PSU tester said the PSU was dud. What happened? The 20-sockets PSU had been running the old IDE-only MOBO, but the 2x2=4-way socket yellow-black hadn't been used. No MOBO pins. If the 2x2=4-way yellow-black supply had been drastically faulty, the old IDE-only MOBO, would not have detected the problem. Not connected. I guess? Verify the 2x2 has the wires in the right place ? The 2x2 is 'keyed' and can't be misconnected? This 2black+2yellow wires wasn't used in the previous PC, which worked ok with this PSU. http://www.playtool.com/pages/psucon...onnectors.html WoW!! Thanks, nice info. I'm not sure there's a good reason for the electrolytic to explode. An electrolytic will explode if you apply a reverse potential across it. That shouldn't have happened in this case. An electrolytic can fail if you exceed the working voltage That could happen, for example, if the 12V rail shorted to the 5V rail, lifting the 5V rail to 12V. Yes, but how could any reverse or excess voltage exist, when the PSU was tested/confirmed: running the old PC previously. Unless it was from the previously unused 2x2. You didn't confirm that using a 20-way-socket on a 24-way MOBO can't cause damage, because the extra 4 are in parrallel to spread the increased current, as the PC industry used more current? If you draw overcurrent from the supply, that increases the ripple current flow in the output capacitors. But I don't know if ripple current through the ESR of the capacitor, will cause it to explode like that. I don't really know what a ripple current failure looks like. Power supplies can have OCP and OVP, but they can be set so high that they don't trigger. And in the case of a cheap power supply, the feature may be missing entirely. A $20 PSU might not have OCP and OVP. If it was my supply, I would take it outdoors, remove the four screws from the top of the PSU, remove the cover and take a picture. Don't poke anything in there, just look. Then put the cover back on (so no one else can poke in there either). Write "blown" on the lid, so when your neighbor finds it in the garbage can, they won't be plugging it in :-) You may be able to tell from which capacitor is blown (one of the tiny ones on the output side), as to what the failure mechanism was. If the explosion was really loud (caused temporary deafness), it could be the primary side capacitor that failed. That's the bigger one in there, and those don't normally blow. Paul If I get a new PSU, it may be destroyed by the now destroyed MOBO? What incremental tests can I do? == TIA. |
#4
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PSU type compatibility?
wrote:
You didn't confirm that using a 20-way-socket on a 24-way MOBO can't cause damage, because the extra 4 are in parrallel to spread the increased current, as the PC industry used more current? You can run a 24 on a 20, or a 20 on a 24, as long as the alignment is correct. To do a 24 on a 20, where the 24 is a solid strip, there cannot be any components in the way, in the overhang area. (The Playtool site has pictures of these cases.) If you plug a 20 PSU into a 24 motherboard, there is only one yellow wire and not two. If you plug in two NVidia 6600 video cards (2x4=8amp load), this is more than you might recommend for a single 6amp wire. So yes, 20 onto 24 works, but don't use too many video cards. They draw 12V from their PCI Express slot. And the more expensive the video card gets, the less power it draws from the slot. And the more power it draws from the 2x3 or 2x4 end connectors. An expensive video card draws 2 amps from 12V, from the slot. You could easily run two expensive cards from a 20 pin PSU, but of course, you would be entirely lacking the number of 2x3 or 2x4 connectors, so the application would be a failure. You won't find a 20 pin PSU with four PCI Express power connectors on it. But if you have an el-cheapo build, an Intel CPU where the GPU is inside the CPU, you can easily run the 24 pin motherboard in that case, off a 20 pin, with nothing to worry about. If I get a new PSU, it may be destroyed by the now destroyed MOBO? What incremental tests can I do? == TIA. Absolutely that can happen. That is called a "domino failure", where damage is passed from item to item. Some posters to the newsgroups ruin three items before they determine "maybe I should stop". This is one of the recognized dangers of being a home repair person. Most of the time, you figure it out and fix it. But sometimes, instead it becomes very expensive and you curse your luck. In your case, you can: 1) Use an ohmmeter and check the readings between rails. Is 3.3V shorted to 5V ? Is 5V shorted to 12V ? Are any of them shorted to ground ? You will need a lesson from someone, in interpreting dynamic readings. If the multimeter reading rises and rises, you're charging a capacitor. That's an example of a response pattern. 2) Open the power supply, and visually figure out which rail the failed cap was on. Then, when ohming out the motherboard, you use that information, to select what wires to start checking for short circuit conditions. And I measure risk with symptoms. Plenty of people have a PSU quit, when the OCP or OVP kicks in and the circuit stops. They can mix and match components at home, and learn stuff. If a second combination causes the PSU to quit, that's a data point. There's no explosion. Whereas, you've had an explosion. That means there is a definite risk factor, compared to the guy where the PSU just switched itself off and played dead. If your symptoms are bad enough, you might never use either item again. This is your call to make. And while it may not seem fair, I sometimes recommend people take their broken kit to a computer shop. And have it blow up some of their gear. Which is the alternative if you simply must get the box working again. You can tell them exactly what happened, so they can weigh the danger to their collection of scrap equipment. I've not heard of a computer shop refusing to test something, but there is always a first time. And there are certainly "safe" pieces of test gear. There are professional power supply testers, that are fully protected. And there are bed of nails motherboard testers, that can survive insults on the production line. And if you do manage to blow one of those, the circuit cards can be individually removed and replaced. So at the factory, they "have no fear", because they have very expensive test equipment. ******* We can take this supply, and perform a thought experiment on it. http://www.pavouk.org/hw/en_atxps.html Look on the right hand side of the diagram. Now, short +5V to -12V. The 5V circuit has much lower impedance, and it "wins". It charges C28 to 5V. But, the potential is applied the wrong way around. C28 is reverse biased. The supply driving +5V is muscular and won't take no for an answer. C28 explodes. So if I traced the wire loom on the 20 or 24 pin, saw which colored wire was joined to that exploded C28, I might start checking how the -12V wire, got shorted to something with a more positive potential. On the motherboard end, I check from -12V to +3.3V, -12V to +5V, looking for signs of a dead short (a rail-to-rail short, rather than a rail-to-ground short). Paul |
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