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#1
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Dell PC blinking yellow
Dell Optiplex 755 is not boot up and flashing yellow only not power go through MB. Google search is all saying there is problem either on PSU and the mother board. I connected other PSU on Dell and found no problem and I am using that PSU on Dell PC now. I also connected the Dell PSU on other computer and found no problem either. So basically Dell PSU and MB are Ok. Why the Dell PSU is not only working on Dell PC? |
#2
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Dell PC blinking yellow
On 08/01/2019 01:39 PM, RainbowMan wrote:
Dell Optiplex 755 is not boot up and flashing yellow only not power go through MB. Google search is all saying there is problem either on PSU and the mother board. I connected other PSU on Dell and found no problem and I am using that PSU on Dell PC now. I also connected the Dell PSU on other computer and found no problem either. So basically Dell PSU and MB are Ok. Why the Dell PSU is not only working on Dell PC? https://duckduckgo.com/?q=optiplex+b...ight&ia=videos I followed this link https://www.ifixit.com/Answers/View/448789/Blinking+Orange+Light+Only because it specifically mentioned 755. I'm not going to watch the video because I don't have a Dell, don't want to ever have one, Dell sucks, F*CK DELL. |
#3
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Dell PC blinking yellow
On Thu, 1 Aug 2019 22:43:56 -0700, Banders wrote:
I followed this link https://www.ifixit.com/Answers/View/448789/Blinking+Orange+Light+Only because it specifically mentioned 755. I'm not going to watch the video because I don't have a Dell, don't want to ever have one, I don't have one either but I was curious. He performed witchcraft with the power supply wires. Scary. Dell likes to make non standard changes to standard things like the ATX power connector. Maybe they wanted to be proprietary like IBM mainframes back in the 70s. That strategy helped IBM corner the mainframe market, but drove them out of the PC market. Too bad Dell didn't learn the lesson. |
#4
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Dell PC blinking yellow
T. Ment wrote:
On Thu, 1 Aug 2019 22:43:56 -0700, Banders wrote: I followed this link https://www.ifixit.com/Answers/View/448789/Blinking+Orange+Light+Only because it specifically mentioned 755. I'm not going to watch the video because I don't have a Dell, don't want to ever have one, I don't have one either but I was curious. He performed witchcraft with the power supply wires. Scary. Dell likes to make non standard changes to standard things like the ATX power connector. Maybe they wanted to be proprietary like IBM mainframes back in the 70s. That strategy helped IBM corner the mainframe market, but drove them out of the PC market. Too bad Dell didn't learn the lesson. Dell only used non-standard ATX wiring for a couple of years. They switched back to standard after that. The video referenced, is a horrible idea. The dude is playing with PS_ON# , that's an input to the PSU, and is a "level". You ground PS_ON# for as long as you want the PSU to run and the fans to turn. The computer has a button on the front. It is a normally open, momentary contact, push button. When you depress the switch for a fraction of a second, one of the "edges" of the pulse signal causes the logic on the motherboard to "latch" the pulse and present a "constant level" on the PS_ON# signal. That's the green wire. This stuff is all detailed in the ATX spec, of which there are three versions, and this picture is from the newest version. The newest version, with 24 pins, was created to suit the PCI Express era and the need for a bit extra +12V current. And that's carried on a yellow wire in the four pin section added to the connector. https://i.postimg.cc/4xY5d4XK/standa...-pin-power.gif ******* This does not explain why the light is flashing on the front panel. Front panel LEDs can use one or two-color LEDs. The front panel LED flashes when the computer is asleep. On older computers, the steady level on the LED might be a red LED, and when the computer is sleeping, that red LED blinks once per second. You can, however, use a two-color LED, two wires, and two GPIO signals to control it. For example, a green-yellow LED. GPIO_0 ----+----+ GPIO_0 GPIO_1 | | --- --- 0V 0V (no light) green \ / /\ yellow 5V 0V green --- --- 0V 5V yellow | | 5V 5V (no light) GPIO_1 ----+----+ This makes it possible for a two wire pair, running from two GPIO signals, to run one bi-color LED. And make two colors of light. If GPIO_0 is held at 0 volts, you can "flash" a 5V signal on GPIO_1 and make a "flashing yellow" light. ******* Well, this is great and all, but the mystery part is: "What feature of a Dell power supply is different enough, to flash the front panel at startup?" I don't know the answer to that. There was at least one Dell model, where the power supply itself had a LED on the back, and it was a "self-test" LED. It was never clear what the self-test was doing. If that supply was bad, it would light the LED on the back. The supply has the "PWR_OK" signal, which is supposed to assert when all levels are "close to full value". When the 12V signal is 11V or greater, that would be a good time to show "PWR_OK". That typically happens about 35 milliseconds after PS_ON# is asserted to the supply. Now, is there an additional signal from the power supply ? Is the additional signal carried on a separate wire pair ? Dunno. These are things a clever repair person would be looking for. Differences. Differences between "bog standard" and "what Dell has done". But the grossly wrong wiring pattern (wires moved around on the 20 pin nylon shell), that was a few years before the Optiplex 755. And if you miss that, plugging in the wrong supply, can ruin stuff. If this is a self-test feature, then there needs to be a means to get the intelligence from the supply to the motherboard (or directly to the front panel LED). All the pins on the main connector have a function, so Dell can't really hijack them for fun. Paul |
#5
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Dell PC blinking yellow
I reset the bios and reflush Dell the PSU and MB( because some voltage still left over even though I completely turned off the system as some online user recommend) and tried again it was working again. I thought I fixed finally but the next morning I turned on again this time it is completely dead. But the PSU still ok and the MB is ok too. I am using 24-pin other PSU and no problem. Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA (since this PSU only has 2 SATA cable) and the strange thing is Windows reported SATA drive as PATA drive I guess since the 3.3V orange wire is unconnected. |
#6
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Dell PC blinking yellow
RainbowMan wrote:
I reset the bios and reflush Dell the PSU and MB( because some voltage still left over even though I completely turned off the system as some online user recommend) and tried again it was working again. I thought I fixed finally but the next morning I turned on again this time it is completely dead. But the PSU still ok and the MB is ok too. I am using 24-pin other PSU and no problem. Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA (since this PSU only has 2 SATA cable) and the strange thing is Windows reported SATA drive as PATA drive I guess since the 3.3V orange wire is unconnected. On SATA, the 3.3V rail hardly matters. Both SATA and IDE drives of the 3.5" variety, use 5V and 12V on the SATA. At 2.5", 5V alone is usually sufficient for the task (even on SSDs). 3.3V is used on some SSDs with microSATA connectors, which is a case where you'd want the 3.3V to be present. I have not seen a reference to such things for some time, and suspect they disappeared from the market. And there is one other case where the 3.3V is important. PWDIS. https://web.archive.org/web/20181223...isable-pin.pdf "There is a simple fix if you find yourself in a situation where an Ultrastar SATA HDD is not spinning up. By using a simple “Molex to SATA” power (no 3.3V power...) connector (Figure 1) to supply power to the HDD, you can usually eliminate the problem. Changing the power connector effectively removes power from P3 (Pin 3) and allows the drive to spin up normally." A pinout listing PWDIS is shown here. I think Pin 11 can drive a LED, as an activity indicator, but I've not heard of anyone hacking that and proving that all drives have that capability. https://pinoutguide.com/Power/sata-power_pinout.shtml Paul |
#7
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Dell PC blinking yellow
"RainbowMan" wrote in message
... I reset the bios and reflush Dell the PSU and MB( because some voltage still left over even though I completely turned off the system as some online user recommend) and tried again it was working again. I thought I fixed finally but the next morning I turned on again this time it is completely dead. But the PSU still ok and the MB is ok too. I am using 24-pin other PSU and no problem. Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA (since this PSU only has 2 SATA cable) and the strange thing is Windows reported SATA drive as PATA drive I guess since the 3.3V orange wire is unconnected. I read, a long time ago, that holding the power button in after isolating the power, drains the charge in the capacitors. Whether this is true, I don't know, but I've done it ever since. -- Regards wasbit |
#8
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Dell PC blinking yellow
wasbit wrote:
"RainbowMan" wrote in message ... I reset the bios and reflush Dell the PSU and MB( because some voltage still left over even though I completely turned off the system as some online user recommend) and tried again it was working again. I thought I fixed finally but the next morning I turned on again this time it is completely dead. But the PSU still ok and the MB is ok too. I am using 24-pin other PSU and no problem. Only adjustment is I converted 4-pin PATA pinout to 15-pin SATA (since this PSU only has 2 SATA cable) and the strange thing is Windows reported SATA drive as PATA drive I guess since the 3.3V orange wire is unconnected. I read, a long time ago, that holding the power button in after isolating the power, drains the charge in the capacitors. Whether this is true, I don't know, but I've done it ever since. The power drains on its own too. It depends on which "edge" of the power signal which is latched, as to when the draining occurs. 5--------------------- \ +5VSB voltage 0 \ ----+ +--------- | | \ Front panel button +------+ \ (low is active) -----------+ | PS_ON# (low is active) +-----------xxxx no-drive when no-5VSB starts to drain There are two converters running off a common 300V+ capacitor. The +5VSB converter is always running when the switch at the back is on. After about 30 seconds, the +5VSB drains on its own when there is a loss of AC. Pressing the front panel switch and releasing, starts the main converter running. It cannot run for too long, since the caps have limited holdup time (16msec maybe at full load). The main converter may die out first, as at some point there isn't enough 300V+ left to operate it. Or, the PS_ON# transistor may lack the ability to keep PS_ON# at zero volts. The +5VSB is probably the last one to wink out. This changes the +5VSB discharge time from 30 seconds to a couple seconds. Since no active element clamps 3.3,5,12V outputs, we can't say with certainty what residual voltage is present. The VCore motherboard converter would tend to drain +12V to maybe +6V. The VCore converter does not run all the way down to zero volts. The informal evidence, is the secondary outputs drop to zero pretty well, without needing any additional help from users. So while pressing the button accelerates the process a bit, in the end the result is about the same. You save about 28 seconds of the sequence. On Asus motherboards, a green LED on the motherboard is tied to +5VSB. When that LED goes out, it is safe to work on the PC inside. Other brands do not have this. For the brands that do not have this, pressing the button reduces the wait time, but the multimeter is your best bet for determine +5VSB is gone. There is a schematic showing the two halves of a supply, here. But this does not show the motherboard logic that controls PS_ON#. PS_ON# comes in around the middle-left of the schematic. http://www.pavouk.org/hw/en_atxps.html Paul |
#9
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Dell PC blinking yellow
On Friday, August 2, 2019 at 2:34:53 PM UTC+8, T. Ment wrote:
Dell likes to make non standard changes to standard things like the ATX power connector. Maybe they wanted to be proprietary like IBM mainframes back in the 70s. That strategy helped IBM corner the mainframe market, but drove them out of the PC market. Too bad Dell didn't learn the lesson. Not just Dell, I have a couple of HP Prodesk SFF PCs. Haswell i7, so still adequate for lots of stuff. Unfortuately non-standard power supplies. If they die, then they will be tossed onto dung-heap. |
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