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Asus P4c800 Deluxe no POST

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    #21
    Re: Asus P4c800 Deluxe no POST

    I think the MOBO doesn't start without CPU but I'm not sure at 100%.

    I hope some experienced member can clarify it.

    Gianni
    "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
    H. J. Brown

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      #22
      Re: Asus P4c800 Deluxe no POST

      For what i've gathered lurking in these forums, older motherboards will turn on without a cpu installed. I've tried it with a couple of pentium ii era motherboards, and they turned on. But it seems newer boards will not, because the voltage regulation module (vrm) chip requires an input present in its vid pins. Through these pins the vrm chip learns the voltage the cpu installed requires. I guess what happens without cpu installed depends of the particular vrm chip used. A more experienced member provided a vrm chip datasheet in another thread, which explicitly described that without a cpu installed, this vrm chip in particular wouldn't provide any output voltage and would shut the power supply down.

      for more information, search the thread titled "Does LGA775 need a CPU to power on? - Gateway Intel D915GAG (Augsburg)"

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        #23
        Re: Asus P4c800 Deluxe no POST

        Ok. So I have two problems. Or MB doesn't work or CPU doesn't work. I can't test CPU because I haven't other socket 478 MB (and CPU) .
        To test if CPU is faulty: the MB beeps and talks are CPU dependent ? If the power on, as you said, is CPU installed dependent, it means a working CPU or whatever CPU ?
        Thanks.
        Bye
        nicolati

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          #24
          Re: Asus P4c800 Deluxe no POST

          q: To test if CPU is faulty: the MB beeps and talks are CPU dependent?
          a: I guess it depends of how the motherboard manufacturer implemented these features. I'm used to deal with the cheapest motherboards, specially pcchips. A pcchips motherboard seems to need a functioning cpu and RAM to emit beep codes. Example: if you don't have a good dimm module installed, the system seems dead. It will turn on but it will not POST. This makes sense if the beeps are implemented via software, (a BIOS program). Without cpu and RAM, you can't execute this.
          Better hardware seems to implement the beep codes closer to the hardware. I have a i845 based intel motherboard that emits beeps even without any RAM installed. I guess this needs more electronics.

          q: If the power on, as you said, is CPU installed dependent, it means a working CPU or whatever CPU ?
          a: The more experienced users of this forum recommend testing the motherboard without a cpu installed after changing bad capacitors on the board, in order to avoid frying the CPU if the work is badly done. They only connect a PSU to the motherboard and turn it on to measure with a multimeter the vrm output voltage, to make sure this voltage is at least in range. You don't accomplish much with this test. It's very basic. If it turns on, it only means there isn't a short circuit on the motherboard that is obvious to the vrm chip and PSU protection circuits, or a V5sb shortcircuit.

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            #25
            Re: Asus P4c800 Deluxe no POST

            fire it up and measure vdimm,vcore.
            hopefully you have a dvm.

            Comment


              #26
              Re: Asus P4c800 Deluxe no POST

              Originally posted by jpdoe
              q: To test if CPU is faulty: the MB beeps and talks are CPU dependent?
              a: I guess it depends of how the motherboard manufacturer implemented these features. I'm used to deal with the cheapest motherboards, specially pcchips. A pcchips motherboard seems to need a functioning cpu and RAM to emit beep codes. Example: if you don't have a good dimm module installed, the system seems dead. It will turn on but it will not POST. This makes sense if the beeps are implemented via software, (a BIOS program). Without cpu and RAM, you can't execute this.
              Better hardware seems to implement the beep codes closer to the hardware. I have a i845 based intel motherboard that emits beeps even without any RAM installed. I guess this needs more electronics.

              q: If the power on, as you said, is CPU installed dependent, it means a working CPU or whatever CPU ?
              a: The more experienced users of this forum recommend testing the motherboard without a cpu installed after changing bad capacitors on the board, in order to avoid frying the CPU if the work is badly done. They only connect a PSU to the motherboard and turn it on to measure with a multimeter the vrm output voltage, to make sure this voltage is at least in range. You don't accomplish much with this test. It's very basic. If it turns on, it only means there isn't a short circuit on the motherboard that is obvious to the vrm chip and PSU protection circuits, or a V5sb shortcircuit.
              Q1: I remember that I removed BIOS chip and beeps there are, so hardware implementation I think. And one time it said me "No CPU installed", when CPU there wasn't.
              Q2: that's problem. My MB doesn't power on without CPU. It try, but after 1 sec or less it shot down.
              Bye
              nicolati

              Comment


                #27
                Re: Asus P4c800 Deluxe no POST

                Originally posted by kc8adu
                fire it up and measure vdimm,vcore.
                hopefully you have a dvm.
                Ok, but where i test vdimm and vcore. I don't know the points.
                Bye
                nicolati

                Comment


                  #28
                  Re: Asus P4c800 Deluxe no POST

                  I long for the days when all you had to start a pc was flip a switch. ATX and ACPI complicated things. I don't really know the components involved in an atx motherboard startup. I have an amd k7 motherboard I can't start up, and I have been looking for information in this forum about it. I didn't find much. I learned quite a lot in the process, though. But I'm still a newbie troubleshooting motherboard electronics.
                  I suppose the options are:
                  1- burned chipset
                  2- burned power on circuitry
                  3- shorted V5sb circuitry
                  4- shorted non V5sb circuitry (circuits feeded by other voltages)

                  In case 4- you will see the system fans (inside the PSU, on the cpu heatsink) twitch when you push the ON button.
                  In case 1- you're out of luck.
                  In case 2- I can't help you. I skimmed a few datasheets of the chips in my k7 motherboard, and it seems the chip that implements the legacy i/o ports (The Low Pin Count -LPC- Interface chip) and southbridge are involved. At that point I gave up.
                  In case 3- I've seen people recommend measuring the V5sb voltage at the atx connector, with the PSU connected to the motherboard, or even better, in some point in the motherboard. I don't know which are those points, tough.
                  If you feel confident enough (IF YOU GET ZAPPED IT'S NOT MY FAULT) you could look for the atx PSU, PCI and dimm pinouts (http://pinouts.ru/ is good) and start testing. The idea is to determine if some device is shorted, and getting all the V5sb amperage for itself.
                  In case 3- It would be nice if there was a way to avoid this circuit by forcing the PSU to start, while connected to the motherboard. I never tried it, and it seems a bit dangerous to me.

                  Comment


                    #29
                    Re: Asus P4c800 Deluxe no POST

                    Sorry for the last post. Just now I understood that your motherboard, without cpu installed, starts and then shuts down after less than 1 second. I've never seen that behaviour. Maybe someone else can help you.

                    Comment


                      #30
                      Re: Asus P4c800 Deluxe no POST

                      Originally posted by nicolati
                      Ok, but where i test vdimm and vcore. I don't know the points.
                      Bye
                      nicolati
                      vcore is across the large lytics nearest the cpu.
                      vdimm lytics nearest the dimms.

                      Comment


                        #31
                        Re: Asus P4c800 Deluxe no POST

                        For what it's worth, I think every time I've tried measuring Vcore without a CPU I just got 0.0v. Seems to be typical behavior, but I haven't done it very many times. I expect most VRMs are designed to do this in the lack of a VID signal. If it produces something huge then at least you'll know it's not safe to plug a processor into it.


                        For memory, it's not always obvious which caps are connected to Vmem. I've worked this out at the socket before so I've attached a picture (I'm assuming you have 184-pin DDR). I had to crop it to make it small enough to post, but the picture is showing the short side of the socket (short side of the notch key). It's showing the underside of the board but you can translate that to the top side so you can measure from above.
                        To confirm you're in the correct corner of the socket - the 5th and 13th pin from the end are both on Vmem and should measure no resistance to each other. Once you've confirmed that, you can use either point on the positive probe and put the negative on some easy ground point (I use the PSU casing).

                        Not sure what to expect at Vmem with the way it's shutting itself off. But I guess if it shoots to 5V or something you'll know you have a problem.
                        Attached Files

                        Comment


                          #32
                          Re: Asus P4c800 Deluxe no POST

                          Originally posted by kc8adu
                          vcore is across the large lytics nearest the cpu.
                          vdimm lytics nearest the dimms.
                          If you say electrolitic caps, I have one big near DIMM and several near CPU socket.
                          Bye
                          nicolati

                          Comment


                            #33
                            Re: Asus P4c800 Deluxe no POST

                            Hi, nicolati. Please check the CMOS battery voltage. You should read around 3Volt. Some ASUS mobos won't power up if CMOS battery is flat.

                            There is a possibility that the BGA 478-pin socket (CPU) has solder crack. This is very common for P4-478 mainboards. Intel designed CPU heatsink put too much stress onto the mainboard. You can see mainboard warp after installing the heatsink From my past experience, if ur mainboard doesn't beep or post even all voltages, eg. CPU Vcore, Vdimm, Vagp are fine, and no IC gets hot, it could be due to BGA socket problem.

                            In the past, I had successfully resurrected few mainboards by heating up the solder side of 478-pin BGA socket using Hakko Hot Air blower.

                            Comment


                              #34
                              Re: Asus P4c800 Deluxe no POST

                              Hi, battery is fine (3 Volt). I opened the socket and fixed some pins with my hands; maybe I have to fix much.
                              Bye
                              nicolati

                              Comment


                                #35
                                Re: Asus P4c800 Deluxe no POST

                                Hi guys, after my last passed exam at university, I'm free to check this MB.
                                I opened the socket and there is one part of it with pins much in and one part much out. But NOW the MB start without processor. It was only rested for a month... The processor was checked by a friend on another P4C800 and it start for a while, after go in protection and the system shut down. I noticed that the silver thermal compound, if it is out of processor, the system doesn't boot up; so I removed all the compound and much out of hole in the processor (this procedure done AFTER my friend check).
                                However some parts on the MB are cold, like SB, RAM, CPU. I didn't check the regulator voltage yet.
                                Bye
                                nicolati

                                Comment


                                  #36
                                  Re: Asus P4c800 Deluxe no POST

                                  mhhh... would be interesting if you get that board back to life..

                                  i've got a P4C800-E Deluxe here.. doesn't do anything useful..
                                  random beeps, no POST (never seen that thing POST...)

                                  tried everything... caps are okay... voltages all OK.. CMOS reset.. reflashed the BIOS on another board... but still nothing...
                                  and the beep codes are some weird ones that aren't even documented.. what the hell..?!?


                                  last thing i thought about was the socket...
                                  but i don't know how to fix that one as its a BGA type one... and i don't have a hot air gun or something like that :/

                                  Comment


                                    #37
                                    Re: Asus P4c800 Deluxe no POST

                                    Neither I have an hot air station, but the problem could be the SB. I have to re-check the voltages... I have NO BEEPS or voice in speakers.
                                    Bye

                                    Comment


                                      #38
                                      Re: Asus P4c800 Deluxe no POST

                                      hello
                                      my P4C800 is dead psu cks good unpluged, but pluged in (everything removed) ps fan turns for around .5sec
                                      row of caps near cpu mesures 9 ohms
                                      shorted?
                                      how do i find the shorted one short of taking all out?
                                      thanks for any help

                                      Comment


                                        #39
                                        Re: Asus P4c800 Deluxe no POST

                                        Answered in poly mod thread.

                                        https://www.badcaps.net/forum/showthread.php?t=13001

                                        Please DO NOT post in more that one thread as it confuses everyone who is answering.

                                        T
                                        veritas odium parit

                                        Comment

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