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Unable to turn off the PC -- weird

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    Unable to turn off the PC -- weird

    Hi everyone. The motherboard is an ASUS P3B-F. It uses an ATX power supply. When in DOS, the only thing installed on the machine, the power button acts like a reset switch, and reboots the machine rather than turning it off. At first I thought this was an issue with the momentary switch. But I tested by plugging in the switch normally used for reset instead, and the behavior was the same. Is this normal? Could it be the power supply?

    BTW, If I press the power button during post it will turn off the machine, but then the BIOS thinks something went wrong with the cpu/bus frequencies because the machine was not able to complete the post. So now the only way I have to turn the machine is by unplugging it from the wall.

    Thoughts?
    Thanks!

    #2
    What happens if you hold the power button in for 5-10 seconds?

    Comment


      #3
      What the power switch does on ATX systems can be set up in the BIOS. Change it to "Instant off".

      Comment


        #4
        Originally posted by Robbbert View Post
        What happens if you hold the power button in for 5-10 seconds?
        Originally posted by Timo W. View Post
        What the power switch does on ATX systems can be set up in the BIOS. Change it to "Instant off".
        Thanks for the replies!!

        It has 2 modes: Soft Off and Suspend. Soft Off immediately restarts the computer like the reset switch. Suspend puts the screen in suspend mode (blackens it) though the HDD still spins… till a keyboard key is pressed. Then it comes back up.

        Holding the power button for 4-5 seconds turns the computer off and it remains off till you release the button. When you release it it boots back up again.

        The way I’m turning it off now is to reset it, then on booting up enter the bios, and once I’m on the bios screen I can press the power button, and from there it turns it off.

        Comment


          #5
          That sounds like a broken PSU then. Could be just the button's debouncing cap, or something more serious.

          Comment


            #6
            Originally posted by Timo W. View Post
            That sounds like a broken PSU then. Could be just the button's debouncing cap, or something more serious.
            Okay. I replaced the PSU. The case calls for an odd size, a hair less tall than modern PSUs, and the motherboard connector only has 20 pins instead of 24. I tried the only PSU I had that had an ATX with 24 pins where 4 were in a separate breakaway molex. But this replacement turned out to have the -5 rail at -6.1. It booted, and the motherboard told me the issue with the -5 rail.

            The behavior was… the power button still acting as reset button, but if pressed for 4-5 seconds the computer would turn off and stay off, as opposed to boot back up as before.

            Would you try to get another 20 pin capable PSU with a good -5 rail? Thoughts? Thanks!

            Comment


              #7
              ATX is ATX, the PSU size should be the same. The only difference between PSUs now vs. back then is that most PSUs now have bottom mounted fans, where as PSUs back then were usually rear mounted fans. This can cause the size discrepancy you're talking about from the fan grille. There are still a few decent rear mounted fan units out there, they're just a bit hard to find.

              What PSU did you get? It sounds like an IED.

              Also, you don't need the -5v rail at all, unless you have some ancient ISA card that requires it. -5v stopped being relevant in the late Pentium era when the ISA bus did, because that's the only place it's used. Some boards do annoyingly have power protection circuits that prevent the board from booting when the -5v rail is missing, but I wouldn't think yours would have that.

              As for the 20+4 pin ATX, you should be able to use a 24 pin ATX connector and just overhang the four pins that aren't used, it looks like there's enough room to do it. Many of the lower wattage PSUs still have 20+4 pin standard though.

              Comment


                #8
                There are also 24-to-20 pin short adapter cables, but those never made any sense to me for the reason posted above. Somewhat akin to using a 4 pin fan on a motherboard with a 3-pin connector--just ignore the extra.

                That ASUS board didn't come out of an HP PC, did it? HP was notorious for checking for all manner of strange things.
                Reach me: vcfblackhole _at_ protonmail dot com.

                Comment


                  #9
                  Hi everyone, thanks again for all the help!

                  Originally posted by Chuck(G) View Post
                  There are also 24-to-20 pin short adapter cables, but those never made any sense to me for the reason posted above. Somewhat akin to using a 4 pin fan on a motherboard with a 3-pin connector--just ignore the extra.

                  That ASUS board didn't come out of an HP PC, did it? HP was notorious for checking for all manner of strange things.
                  This seems to be a custom build, not HP. I managed to get a 3rd power supply. This one has the 20 pin connector. So...

                  I replaced
                  - The Power Supply by a 3rd one (see pics)
                  - The Power Button by a new one (see pics)

                  Behavior is:
                  - DOS boots, press the power button, computer turns off and immediately turns back on
                  - If I press the power button before DOS boots, it does turn off the computer normally
                  - Board still complains about -6.1V, which leads me to believe the diagnostics is bogus, as these are totally different power supplies (Anted and Seasonic)

                  I checked the ASUS website https://www.asus.com/us/supportonly/...HelpDesk_BIOS/ and next I'll try and update the firmware. Currently running 1003.A. Updating to 1006.


                  20210914_130148913_iOS.jpg 20210914_130143961_iOS.jpg
                  Last edited by Phase; September 14, 2021, 06:11 AM.

                  Comment


                    #10
                    I updated the BIOS and still have the same problem. I also removed all cards but the video card, and swapped in a new set of memory modules. None of it made a difference. It seems that the motherboard is the culprit.

                    Comment


                      #11
                      Is 'PWR Up On PS2 KB/Mouse' enabled in the bios? According to the manual (https://www.asus.com/us/SupportOnly/...lpDesk_Manual/) the power supply needs to supply at least 300mA on the +5 standby line. Maybe the standby is getting pulled down and causing a reset?

                      BTW, awesome of ASUS to keep the manual available.

                      Comment


                        #12
                        You need to open that Antec PSU and check it for failed capacitors. Antec PSUs from 2000-2008 are known to use shit capacitors that leak and fail. I've personally recapped at least two dozen of those "Basiq Power" models. The one you have is an oddball, the Basiq Power model started in the early 2000s, but the case on yours has the design from later 2000s True Power models.

                        The -5v rail being so far out of spec could definitely be caused by a failed capacitor.

                        If you open it, you'll likely find a mix of Fuhjyyu, Asia X, Teapo and OST capacitors, all of them are garbage, but Fuhjyyu is the worst of the bunch.

                        Comment


                          #13
                          Originally posted by GiGaBiTe View Post
                          You need to open that Antec PSU and check it for failed capacitors. Antec PSUs from 2000-2008 are known to use shit capacitors that leak and fail. I've personally recapped at least two dozen of those "Basiq Power" models. The one you have is an oddball, the Basiq Power model started in the early 2000s, but the case on yours has the design from later 2000s True Power models.

                          The -5v rail being so far out of spec could definitely be caused by a failed capacitor.

                          If you open it, you'll likely find a mix of Fuhjyyu, Asia X, Teapo and OST capacitors, all of them are garbage, but Fuhjyyu is the worst of the bunch.
                          Thanks!! The Antec is the second alternate power supply I tried and in both the mobo reported the same -6.1V. I’m getting a brand new Seasonic Focus GX-550 today for another build and I’ll try it here first, though the 24 to 20 pin cable may only arrive in a few days. Will see if the mobo reports the same problem with the 3 of them.

                          Originally posted by eswan View Post
                          Is 'PWR Up On PS2 KB/Mouse' enabled in the bios? According to the manual (https://www.asus.com/us/SupportOnly/...lpDesk_Manual/) the power supply needs to supply at least 300mA on the +5 standby line. Maybe the standby is getting pulled down and causing a reset?

                          BTW, awesome of ASUS to keep the manual available.
                          Thanks!! I generally like ASUS, until when something happens… lol. It is still one of my go to brands. All automatic power up/wake up functions are disabled in the BIOS already. So the issue remains

                          Comment


                            #14
                            The only ATX power supplies with -5v would be the very earliest versions. It was removed from the spec in version 1.3. I think the only cards that used it were a version of the Pro Audio Spectrum, one of the Roland midi cards, and one other card. Very unlikely that a power supply with a 24-pin connector (version 2.x?) has -5v.

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