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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Computer power supply capacitors - generic question
I have a generic power supply that had the two main 470uF/200V caps
fail about a year ago (physically leaking, one had the top pretty well opened.) I replaced them with new caps from mouser (computer grade caps and 105c rated), and all was working well. This year, the power supply is again exhibiting problems..upon a cold boot, the computer will do about two reboots before it finally powers up. I was wondering if these voltage ratings on the caps, were too low..seems like they should have higher rated caps then this I would think. On the -12V line, C1 is rated 16V On the +12V line, C2 is rated 16V On the +5 or -5V line, C3 is rated 16V On the +5 line, C4,5 is rated 10V On the +3.3V line, C6, C10 are rated 10V and 50V respectively On the +5VSB (+5 Standby I am guessing?), C11,C12, and C13 are all rated 16V Reading from the BIOS, the computer shows these voltages: CPU Co 1.69v +3.3 is reading 2.94V +5V reads 4.99V +12V reads 11.49V -12V reads 11.86 -5 reads -5.25 Battery Voltage (should be 3V) reads 2.88V Standby Voltage (should be +5) reads 4.80V As you can see, +12 Volts is pretty low, as is the +3.3 volt line. I suspect these are what is causing the computer to reboot about two times. Are the 10 volt ratings of C4,C5,C6 all too low? Seems to me they should have put some capacitors that had a little higher rating in order to better handle transient surges, etc? Are the 16V caps also too low for the +/- 12 volt lines? Would 25V have been better or perhaps 50V caps? Or is 50V too high? |
#2
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Computer power supply capacitors - generic question
Actually the measurements are fairly nominal but as cheap as good power
supplies are now days I'd just replace it. At least try a new one in your system to see if it rectifies the boot up problem. "Sal Holland" wrote in message ... I have a generic power supply that had the two main 470uF/200V caps fail about a year ago (physically leaking, one had the top pretty well opened.) I replaced them with new caps from mouser (computer grade caps and 105c rated), and all was working well. This year, the power supply is again exhibiting problems..upon a cold boot, the computer will do about two reboots before it finally powers up. I was wondering if these voltage ratings on the caps, were too low..seems like they should have higher rated caps then this I would think. On the -12V line, C1 is rated 16V On the +12V line, C2 is rated 16V On the +5 or -5V line, C3 is rated 16V On the +5 line, C4,5 is rated 10V On the +3.3V line, C6, C10 are rated 10V and 50V respectively On the +5VSB (+5 Standby I am guessing?), C11,C12, and C13 are all rated 16V Reading from the BIOS, the computer shows these voltages: CPU Co 1.69v +3.3 is reading 2.94V +5V reads 4.99V +12V reads 11.49V -12V reads 11.86 -5 reads -5.25 Battery Voltage (should be 3V) reads 2.88V Standby Voltage (should be +5) reads 4.80V As you can see, +12 Volts is pretty low, as is the +3.3 volt line. I suspect these are what is causing the computer to reboot about two times. Are the 10 volt ratings of C4,C5,C6 all too low? Seems to me they should have put some capacitors that had a little higher rating in order to better handle transient surges, etc? Are the 16V caps also too low for the +/- 12 volt lines? Would 25V have been better or perhaps 50V caps? Or is 50V too high? |
#3
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Computer power supply capacitors - generic question
i have fix a few pc supplys,
try replaceing the caps and resistors that connect to the bases of the two main switching transistors, you see some values like 470k around them as well. check all resistors around them transistors, you may fine one or two near open or high. and check for bad soldering joints. these caps and resistors i call starting resistors and caps. be cairfull thay are dangeres! john "Sal Holland" wrote in message ... I have a generic power supply that had the two main 470uF/200V caps fail about a year ago (physically leaking, one had the top pretty well opened.) I replaced them with new caps from mouser (computer grade caps and 105c rated), and all was working well. This year, the power supply is again exhibiting problems..upon a cold boot, the computer will do about two reboots before it finally powers up. I was wondering if these voltage ratings on the caps, were too low..seems like they should have higher rated caps then this I would think. On the -12V line, C1 is rated 16V On the +12V line, C2 is rated 16V On the +5 or -5V line, C3 is rated 16V On the +5 line, C4,5 is rated 10V On the +3.3V line, C6, C10 are rated 10V and 50V respectively On the +5VSB (+5 Standby I am guessing?), C11,C12, and C13 are all rated 16V Reading from the BIOS, the computer shows these voltages: CPU Co 1.69v +3.3 is reading 2.94V +5V reads 4.99V +12V reads 11.49V -12V reads 11.86 -5 reads -5.25 Battery Voltage (should be 3V) reads 2.88V Standby Voltage (should be +5) reads 4.80V As you can see, +12 Volts is pretty low, as is the +3.3 volt line. I suspect these are what is causing the computer to reboot about two times. Are the 10 volt ratings of C4,C5,C6 all too low? Seems to me they should have put some capacitors that had a little higher rating in order to better handle transient surges, etc? Are the 16V caps also too low for the +/- 12 volt lines? Would 25V have been better or perhaps 50V caps? Or is 50V too high? |
#4
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Computer power supply capacitors - generic question
You haven't specified the Wattage rating of the PSU or the system you expect
it to power. If the boot up problems are caused by the supply being borderline then no amount of swapping caps is going to fix it. A new higher power supply is going to be a lot less trouble and probably the cheapest solution in the end. Pete "Sal Holland" wrote in message ... I have a generic power supply that had the two main 470uF/200V caps fail about a year ago (physically leaking, one had the top pretty well opened.) I replaced them with new caps from mouser (computer grade caps and 105c rated), and all was working well. This year, the power supply is again exhibiting problems..upon a cold boot, the computer will do about two reboots before it finally powers up. I was wondering if these voltage ratings on the caps, were too low..seems like they should have higher rated caps then this I would think. On the -12V line, C1 is rated 16V On the +12V line, C2 is rated 16V On the +5 or -5V line, C3 is rated 16V On the +5 line, C4,5 is rated 10V On the +3.3V line, C6, C10 are rated 10V and 50V respectively On the +5VSB (+5 Standby I am guessing?), C11,C12, and C13 are all rated 16V Reading from the BIOS, the computer shows these voltages: CPU Co 1.69v +3.3 is reading 2.94V +5V reads 4.99V +12V reads 11.49V -12V reads 11.86 -5 reads -5.25 Battery Voltage (should be 3V) reads 2.88V Standby Voltage (should be +5) reads 4.80V As you can see, +12 Volts is pretty low, as is the +3.3 volt line. I suspect these are what is causing the computer to reboot about two times. Are the 10 volt ratings of C4,C5,C6 all too low? Seems to me they should have put some capacitors that had a little higher rating in order to better handle transient surges, etc? Are the 16V caps also too low for the +/- 12 volt lines? Would 25V have been better or perhaps 50V caps? Or is 50V too high? |
#5
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Computer power supply capacitors - generic question
Switching power supplies can be very dangerous, so be careful when you are working on the unit. Given the prices of decent supplies today, I wouldn't waste your time troubleshooting or replacing caps - just replace the supply. Several supply manufacturers, such as Antec, etc. offer excellent supplies for a very low cost. Go to www.newegg.com, or other good online sources, and find you best price on a 300 to 400 watt supply. Don |
#6
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Computer power supply capacitors - generic question
Larry
Computer power supply capacitors - generic question had a cheap PSU where the 16V capacitors for the +12V rail were getting 50V peak spikes, but I saw nothing that high in a better PSU's +12V. From one who has replaced a lot of capacitors. DC voltage plus signal voltage/ripple times two. In your case DC plus ripple times two. . Use milspec capacitors. I suspect the computer grade thing is more marketing hype than anything else. Bob AZ |
#7
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Computer power supply capacitors - generic question
if you buy a new supply, dont throw away the old
one, you can use this supply on other things like op amps. i built a 16 input mixer useing a pc power supply. to run this supply without a computer, connect a 5watt 100 ohm resistor across the 5 volt out to ground, its a dummy load. same for ATX supplys, to fire up an ATX, ground the SP-ON wire. john "Sal Holland" wrote in message ... I have a generic power supply that had the two main 470uF/200V caps fail about a year ago (physically leaking, one had the top pretty well opened.) I replaced them with new caps from mouser (computer grade caps and 105c rated), and all was working well. This year, the power supply is again exhibiting problems..upon a cold boot, the computer will do about two reboots before it finally powers up. I was wondering if these voltage ratings on the caps, were too low..seems like they should have higher rated caps then this I would think. On the -12V line, C1 is rated 16V On the +12V line, C2 is rated 16V On the +5 or -5V line, C3 is rated 16V On the +5 line, C4,5 is rated 10V On the +3.3V line, C6, C10 are rated 10V and 50V respectively On the +5VSB (+5 Standby I am guessing?), C11,C12, and C13 are all rated 16V Reading from the BIOS, the computer shows these voltages: CPU Co 1.69v +3.3 is reading 2.94V +5V reads 4.99V +12V reads 11.49V -12V reads 11.86 -5 reads -5.25 Battery Voltage (should be 3V) reads 2.88V Standby Voltage (should be +5) reads 4.80V As you can see, +12 Volts is pretty low, as is the +3.3 volt line. I suspect these are what is causing the computer to reboot about two times. Are the 10 volt ratings of C4,C5,C6 all too low? Seems to me they should have put some capacitors that had a little higher rating in order to better handle transient surges, etc? Are the 16V caps also too low for the +/- 12 volt lines? Would 25V have been better or perhaps 50V caps? Or is 50V too high? |
#8
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Computer power supply capacitors - generic question
"Mr TUBEAMPS" youfinedout@thomuusnonsence wrote in message
u... if you buy a new supply, dont throw away the old one, you can use this supply on other things like op amps. i built a 16 input mixer useing a pc power supply. to run this supply without a computer, connect a 5watt 100 ohm resistor across the 5 volt out to ground, its a dummy load. same for ATX supplys, to fire up an ATX, ground the SP-ON wire. john Shouldn't a 1/2 Watt 100 ohm resistor be sufficient? 5V / 100 Ohms = 50 ma. 50 ma * 5V = 250 mW, right? Norm |
#9
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Computer power supply capacitors - generic question
On Mon, 28 Jun 2004 15:38:59 +1000, Mr TUBEAMPS youfinedout@thomuusnonsence wrote:
if you buy a new supply, dont throw away the old one, you can use this supply on other things like op amps. that's like using a used bulldozer for a boxgarden. |
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