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#1
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No Power (DELL)
A few days ago a storm came through and kicked the power off for a few
hours. There was no lightening strike involved close by to the best of my knowledge mostly wind. I have one pc {Dell Inspiron i537-3492} hooked up to an expensive ass a.p.c. 500 ( Its surge protection plus battery back up) unit and the other {eMachine} hooked up to a cheap ass bar unit surge protecter only. Go figure the "Dell" is the one that will not power on now. The reset button only slides from left to right as far as I can tell. I've un plugged it and let it sit for a day and tried to power on with the reset in both positions and it will not power on. There is a green light just below the reset button. It's on when you have it plugged into the wall and goes off several seconds after you unplug it. I have the side panel off. I see no visible fuses or breakers. I'm guessing taking out the power supply is next but I am waiting for some advise before going any further. I hope I can fix this my self with a little help from you guys. :-) YIA, DS p.s. and yes... when testing I am pluging directly into a "confirmed working outlet". |
#2
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No Power (DELL)
Doomed Soul wrote:
A few days ago a storm came through and kicked the power off for a few hours. There was no lightening strike involved close by to the best of my knowledge mostly wind. I have one pc {Dell Inspiron i537-3492} hooked up to an expensive ass a.p.c. 500 ( Its surge protection plus battery back up) unit and the other {eMachine} hooked up to a cheap ass bar unit surge protecter only. Go figure the "Dell" is the one that will not power on now. The reset button only slides from left to right as far as I can tell. I've un plugged it and let it sit for a day and tried to power on with the reset in both positions and it will not power on. There is a green light just below the reset button. It's on when you have it plugged into the wall and goes off several seconds after you unplug it. I have the side panel off. I see no visible fuses or breakers. I'm guessing taking out the power supply is next but I am waiting for some advise before going any further. I hope I can fix this my self with a little help from you guys. :-) YIA, DS p.s. and yes... when testing I am pluging directly into a "confirmed working outlet". I don't see a lot in the way of controls on that thing. http://img29.imageshack.us/img29/1551/inspiron537.gif http://support.dell.com/support/edoc...n/sm/index.htm And I don't see a "reset" slider here. There is a jumper for clearing the password. And another jumper for clearing the rest of the CMOS RAM (256 bytes of parameters, which store BIOS settings of one sort or another). http://support.dell.com/support/edoc....htm#wp1200202 ******* The green LED on the motherboard, should be connected to +5VSB from the power supply. The power supply consists of two parts (like, two separate regulators). AC ---- HVDC ------ 5VSB regulator ------ Regulator for 3.3V, 5V, 12V main rails If you want to see a PSU in more detail, to see what I'm talking about, there's a full schematic of one, here. http://www.pavouk.org/hw/en_atxps.html So if the green LED comes on, that means the fuse isn't blown in the ATX supply. And a portion of the supply (+5VSB) is working. For the motherboard to turn on the system, it has the following. +-------------+ PSU --- +5VSB -----------| | | Motherboard |--- PS_ON# --- back to PSU Power_button_on_front ---| | | If the motherboard was severely damaged some how, such that it couldn't send PS_ON#, that would prevent it from starting. If the power supply is damaged on the PS_ON# input, then that could stop it. Some power supplies become "deaf" to their PS_ON# input, and it doesn't matter whether logic 0 or logic 1 is sent to the supply - nothing happens. And that would be a dead supply. To test the supply, we'd normally pull it (making a diagram of where all the wires go, and what color wire is on which side of the connector). Then, using a paper clip, we'd connect PS_ON# to COM. That would be performing the same function as the motherboard was performing, namely, pulling the PS_ON# signal towards ground or zero volts. If the PS_ON# signal is floating, it floats up to a 5V potential. And to turn on the main rails, the motherboard "tugs down" on the PS_ON# signal, sinking a couple milliamps, and the logic low level on PS_ON# tells the supply to start, spin the power supply fan, and so on. The wiring information for a 24 pin supply is here, page 37. You could test the power supply, stand alone, by connecting pin 15 to 16 (black and green wires). Any black wire would do, but 15 is pretty close to 16. The "best practices" recommendation, is to have a dummy load connected to the supply, when connecting pin 15 to pin 16. If you have an old disk drive, that would be an example of a dummy load. (If I don't mention that, someone will only complain :-) ) The idea of the dummy load, is to draw an ampere or two from some rail on the supply, as the supply is not push-pull in design, only pushes, and a slight load performs the pull function and helps keep the supply regulated. I've not had a problem here, testing without a dummy load, but I have to mention the dummy load for sake of completeness. Some supplies, on the label, actually mention they have a minimum load spec. I no longer see supplies with such a crappy design feature. http://www.formfactors.org/developer...public_br2.pdf So your progress so far, is 1) Green light = good. Means +5VSB is present. That should power enough of the motherboard, for the motherboard to assert PS_ON# to ground level, when the front bezel power button is pressed. 2) Either the power supply is not responding to PS_ON#, or the motherboard is no longer capable of sending PS_ON# to the supply. We can't be sure which has failed. If you owned a multimeter, you can probe the 24 pin connector, while it remains connected to the motherboard. You set the multimeter to volts, like 20V full scale, and clip the black lead to the chassis. The chassis is grounded, same potential as any black wire on the harness. Clipping onto the chassis, is to avoid the danger of shorting something. I use a shiny screw, like on a rear I/O connector, for my electrical connection. With the red lead, you can touch the exposed metal, which sits just inside the plastic shell of the 24 pin connector. Start from power off at the back of the computer. (Note - do *not* change the 115V/230V slider on the supply!) Turn on the power at the back of the computer. The green LED should come on. With the multimeter, verify pin 9 (purple, +5VSB) reads 5.0 volts. Now, check pin 16 (green, PS_ON#) as well, and it should be very close to the same 5.0 volt value. Next, press the front panel power button. Go back to pin 16 (green, PS_ON#) and verify the voltage is very close to 0.0 volts. Acceptable, might be less than 0.8V or so. If it's riding around 2.0V, then the motherboard is having a problem pulling the signal all the way to ground. Closer to zero volts at that point, would be better. Anyway, post back, report your pin 16 readings. The power supply also has a status signal, PWR_OK on pin 8. That's only important if the power supply fan is spinning. It's possible, for the power supply to withhold PWR_OK, even if the power supply fan is spinning. The computer can't boot, until the power supply says it is OK to boot. But that's not even a consideration (don't need to measure it), unless the power supply fan starts to spin. The status is only important, if you get as far as the main rails come on, and the 3.3V, 5V, 12V are present, and the motherboard still won't run. In such a case, you could then check PWR_OK and see if the state indicated it was ready to run. The motherboard has its own internal "I'm OK" logic as well, but tracing that down is a lot tougher. Without a multimeter, about all you can do, is pull the supply, and connect PS_ON# to COM for a test, with the switch on at the back of the supply. If the fan spins, the supply could be OK, and maybe the motherboard has a problem. If the fan doesn't spin, then maybe the main portion of the ATX supply is bad. That's about the best we can do, in terms of diagnosis without a multimeter. Using the multimeter, if the chassis isn't too crowded, might be a bit easier than pulling the supply, if you haven't done it before. The multimeter can't tell the whole story, except in certain cases (like, you see a good level of zero volts on PS_ON#, 5.0 volts on +5VSB, and the supply still won't start, in which case the second half of the supply is bad). Another small note - in the event the computer will not respond to the front power button, you switch it off at the back for one minute, then switch it on again. Certain faults detected inside the computer, are "latching" type. To clear the latching faults, you remove all power from the computer and let it drain. And then, it should be "re-armed" to detect faults again. I think you've already done that, but again, I have to mention it. Letting it drain, is going to happen when you do your tests above anyway. Paul |
#3
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No Power (DELL)
"Doomed Soul" wrote in message
... A few days ago a storm came through and kicked the power off for a few hours. There was no lightening strike involved close by to the best of my knowledge mostly wind. I have one pc {Dell Inspiron i537-3492} hooked up to an expensive ass a.p.c. 500 ( Its surge protection plus battery back up) unit and the other {eMachine} hooked up to a cheap ass bar unit surge protecter only. Go figure the "Dell" is the one that will not power on now. 1. Unmentioned here is that you reset the APC UPS correctly. The larger ones require a reset after a power outage. 2. APC's advertising stresses their hardware's capacity to protect you from damage. APC has an interest in restarting your Dell a.s.a.p. -- Don Phillipson Carlsbad Springs (Ottawa, Canada) |
#4
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No Power (DELL)
Paul Wrote:
I don't see a lot in the way of controls on that thing. And I don't see a "reset" slider here ------------------------------------------------ Thanks I didn't realize that fact. I've had this same event occur in the past with older models and All I had to do was press a reset switch in the back. When I originally posted I was hoping there was a simple reset-switch/ breaker/fuse or some sort of safety mechanism i was missing. Big thanks on posting the diagnostic instructions. It will be at least a few more days before I can dig that deep into it. Luckily the tower is not crowded at all and most everything is easy to access. The power supply should be fairly simple to remove. I can buy a multi meter fairly cheep. ------------------------------------------------ Paul Wrote: To clear the latching faults, you remove all power from the computer and let it drain. And then, it should be "re-armed" to detect faults again. I think you've already done that, but again, I have to mention it. Letting it drain, is going to happen when you do your tests above anyway. ------------------------------------------------ After I read this I pulled the BIOS battery and let it sit for another 36 hrs just in case it matters.lol Well it didn't :-( Oh and there is no fan running at any time. I have the voltage switch on back set on 115v. (I live in U.S.) One more question before I take out the supply. Is it possible that there may still be a simple safety mechanism (reset/fuse/switch) I'm missing? ------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------- Don Wrote: 1. Unmentioned here is that you reset the APC UPS correctly. The larger ones require a reset after a power outage. ----------------------------------------------- Yes I did. :-) ----------------------------------------------- 2. APC's advertising stresses their hardware's capacity to protect you from damage. APC has an interest in restarting your Dell a.s.a.p. ----------------------------------------------- Thanks!! I hadn't even thought of that angle. I will pursue it. Thanks again, D.S. |
#5
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No Power (DELL)
Doomed Soul wrote:
One more question before I take out the supply. Is it possible that there may still be a simple safety mechanism (reset/fuse/switch) I'm missing? You tell me you have a green LED glowing, when the power supply is plugged into the wall AC, and the rear switch on the supply is in the ON position. That tells me the fuse inside the ATX supply is good. And, that the +5VSB half of the supply is running. We don't know whether it is making exactly 5.0 volts on the +5VSB rail. It could probably tolerate some error in that department and still start. If there is some +5VSB present, the supply main cable (24 pin) is connected up, then it's a matter of the motherboard sending that PS_ON# signal, to get the fan running on the power supply and the main 3.3V/5V/12V rails along with it. There are other faults that could happen, but the fans would be running when that happens. If there is no "main" set of rails running, it's pretty hard for other things to foul up. The power supply could be "deaf" to PS_ON# (damaged). The motherboard could be refusing to send PS_ON# (damaged). One or the other or both could be at fault. In rare cases, you could replace the supply, still no joy, replace the motherboard, and then hear fans. The power supply can be tested stand-alone with the "paper clip test". And some diagnosis of the motherboard, attempted with the multimeter while things are wired up. Paul |
#6
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No Power (DELL)
Start from power off at the back of the computer. (Note - do *not* change
the 115V/230V slider on the supply!) Turn on the power at the back of the computer. The green LED should come on. My dad had me wiring up 3 way toggle switches when I was 6, but I've never taken any electronics courses, All I know is what my Father taught me growing up. I do know how to use an Ohm meter tho and your instructions are easily understood so please be patient with me. I have no idea what the position was originally on the 115/230. Right now I have it set to 115v. I thought it was a reset button like on the older models I've owned in the past. I see no other On/Off switch in the back. Unless 115/230=On/Off? DS |
#7
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No Power (DELL)
Doomed Soul wrote:
Start from power off at the back of the computer. (Note - do *not* change the 115V/230V slider on the supply!) Turn on the power at the back of the computer. The green LED should come on. My dad had me wiring up 3 way toggle switches when I was 6, but I've never taken any electronics courses, All I know is what my Father taught me growing up. I do know how to use an Ohm meter tho and your instructions are easily understood so please be patient with me. I have no idea what the position was originally on the 115/230. Right now I have it set to 115v. I thought it was a reset button like on the older models I've owned in the past. I see no other On/Off switch in the back. Unless 115/230=On/Off? DS That switch is only fatal to the computer, if you live in a 230V country, and switch it to 115V by accident. If you did that, double the rated voltage would get applied to the main capacitor. If you live in a 115V country, and switch it to 230V, the power supply will behave "weakly". Once it is switched back to the 115V position (while powered off), the supply should be its old self again. It is best to only move the slider, with the power off. (Like, if you were in a 230V country, moved the switch, then thought better of it, and moved it back. Doing it with the power off, gives you another chance to think about what you're doing :-) ) The slider can be seen in the schematic of this power supply. It fiddles a connection between the bridge rectifier and the main caps. The 470uF caps store a lot of energy, and help the supply "ride through" short power outages of under a second. The 470uF caps are also why we can use cheap UPS boxes, without the computer crashing when the UPS switches over. The hold-over of the supply is what makes the difference. http://www.pavouk.org/hw/en_atxps.html ******* To use the multimeter: 1) Stick the red and black wire set, in the "volt/ohm" holes, not the "current" hole. I generally *never* measure current with my multimeter. My meter leads always stay in the same two holes. Most of my diagnostics can be completed with voltage. I have a separate meter for current measurements, with a tremendous operating range (up to 400 amps). 2) The meter should be rated for the job. If you're going to measure something which is 1000V, then the meter has to be rated for it. I remember seeing a multimeter ruined in the lab, when an idiot connected one to a super-high voltage supply. The guy was working on his Masters degree in electronics. 3) Set the multimeter to the volts range. If there is something that distinguishes between "AC" or "DC", set that as well. Inside the PC, the voltages are "DC". The only AC would be on the primary side of the power supply. And there is no reason to be working inside there! 4) Clip the black lead to the chassis, which is ground. The chassis is safety ground on the AC side, and is also the zero volt DC potential level of the secondary side. If you have probe tip test leads, you slip an alligator clip over the probe tip, then clip the alligator tip onto a shiny I/O screw in the I/O plate area. You do it this way, so there's no way to short the probe tips together. Big sparks could result if the tips got shorted, and you were measuring +12V. Now, you can make voltage measurements with the red probe, and only move the red probe around. You can stick the red probe, into the back of the 24 pin connector, and get it to touch metal in there. The plastic shell of the connector, prevents the probe tip from shorting two adjacent wires. 5) The multimeter can either be autoranging (which I find annoying), or manually set. Select a voltage range suitable for checking 3.3V/5V/12V like the 20V full scale range. If you set it to 200V full scale range, then the readings will have one less digit to offer you. If you set it to 2V full scale, then all the readings will be "overrange" and the display will flash its displeasure. The meter is only accurate to perhaps +/- 1.5% or so. That's how much the meter can be off by. There are various voltage references, and in a "real" lab, there would be a requirement to calibrate the instruments at regular intervals. I used to get a laugh at work, when these dudes with "extra white" dress shirts would show up, while the rest of us were wearing jeans and casual attire, and they'd spend a week calibrating stuff. I'd never seen any of our test gear, that far out of calibration, but doing the whole lab like that was considered to be some part of ISO9000 compliance. The "extra white" dress shirts were calibrated I guess. Whereas our dingy clothing was in the uncalibrated state. At least it was easy to keep track of where they were located. HTH, Paul |
#8
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No Power (DELL)
I finally found time to open this thing up and look around. Before I
start attempting to perform the readings you posted I first wanted to see if I could find a switch, fuse, reset, or anything. I even pulled the power supply and removed the casing and I could not find anything at all. As far as I can see there is no visible on/off switch or fuse. Only switch I can find is the main switch at the front of the tower. I'm not saying it's not there, I'm just saying I can't find it. In case I'm missing something,... I just wanted to post this before I put everything back together and start testing. DS |
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