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Problem with QDI US491P3 mainboard - dead?

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    Problem with QDI US491P3 mainboard - dead?

    Hi there!

    Here I am with this 486 mainboard recently purchased at a flea market. I cleaned it well, changed the big blue battery with a button cell and powered it on. It does nothing, no beeps, nothing.

    I tried to:

    - Use various CPUs. Tried a DX2-66, a SX-20 and a SX-40. Tried every possible jumper configuration. No results.
    - Use various DRAM modules, following the instructions and configurations from this manual: http://stason.org/TULARC/pc/motherbo...-US486-P3.html. This manual is for the US486, mine is US491 but they have the same layout. No results.

    I used the multimeter on the AT power pins and all gave correct values.

    Do I miss something? What do you think?

    Thanks for you help

    #2
    Originally posted by [UFO] View Post
    Hi there!

    Here I am with this 486 mainboard recently purchased at a flea market. I cleaned it well, changed the big blue battery with a button cell and powered it on. It does nothing, no beeps, nothing.

    I tried to:

    - Use various CPUs. Tried a DX2-66, a SX-20 and a SX-40. Tried every possible jumper configuration. No results.
    - Use various DRAM modules, following the instructions and configurations from this manual: http://stason.org/TULARC/pc/motherbo...-US486-P3.html. This manual is for the US486, mine is US491 but they have the same layout. No results.

    I used the multimeter on the AT power pins and all gave correct values.

    Do I miss something? What do you think?

    Thanks for you help

    The board is looking well? Maybe the bios chip isn't there, take a look. Also, remove the battery, and try again. The cpu warms up?

    Comment


      #3
      Yes, the board looks well, no rust, no dirt. The BIOS chip is there (AMIBIOS). CPU warms up, it was one of the first points I checked.

      I will post some pics later to let you have a graphic reference

      Comment


        #4
        Originally posted by [UFO] View Post
        Yes, the board looks well, no rust, no dirt. The BIOS chip is there (AMIBIOS). CPU warms up, it was one of the first points I checked.

        I will post some pics later to let you have a graphic reference

        Are you certain that the speaker is good? the power supply is 100% ?




        I've seen boards that won't boot with a bad battery, and boards that won't boot without a battery, try to remove it, also remove all the cards from the system, if nothing happens, try it only with a vga.

        Comment


          #5
          Does the motherboard have the cache chips? Just asking because it will not POST unless some external cache is installed, the AMI BIOS defaults to external cache enabled and that will prevent the POST if there is no cache, even if the motherboard is configured for no cache. It would go to default configuration when there is no power supplied to the board fom the battery.

          Edit: With the cache removed it may or may not have screen activity when the BIOS goes to default settings.

          One more thing to try, hit the [Delete] key a few seconds after powering on the motherboard and see if it gets you to the BIOS setup.
          Last edited by RJBJR; February 8, 2012, 02:07 AM.

          Comment


            #6
            Hey!

            Here is a macropic of the board, zooming each corner (took it with a cell phone camera, sorry):

            http://img84.imageshack.us/img84/2595/486c.jpg

            Cache chips are all there (down-right). Down-left is the speaker. Well, it is a piezoelectric buzzer, like in the modern mobos.

            RAM is 1MB divided in 256K SIMMs.

            Comment


              #7
              Originally posted by [UFO] View Post
              Hey!

              Here is a macropic of the board, zooming each corner (took it with a cell phone camera, sorry):

              http://img84.imageshack.us/img84/2595/486c.jpg

              Cache chips are all there (down-right). Down-left is the speaker. Well, it is a piezoelectric buzzer, like in the modern mobos.

              RAM is 1MB divided in 256K SIMMs.

              I see that the power supply connector is plugged... are the board properly grounded(hook a ground cable to the holes where you put a screw when the board is on a regular at case)? Did you removed all the cards? Remove even the keyboard and try again. If the IDE cable is connected wrong, the sytem will power up dead like yours(no beep, no post, nothing)

              did you tried to fill all memory banks?

              also, 256k SIMMs, never seen this!
              Last edited by lucasdaytona; February 8, 2012, 04:59 AM.

              Comment


                #8
                Originally posted by lucasdaytona View Post
                I see that the power supply connector is plugged... are the board properly grounded(hook a ground cable to the holes where you put a screw when the board is on a regular at case)?
                Yes, it is grounded.

                Originally posted by lucasdaytona
                Did you removed all the cards? Remove even the keyboard and try again. If the IDE cable is connected wrong, the sytem will power up dead like yours(no beep, no post, nothing)
                Yes, I removed all the cards, although you can see a video card connected in the pics. Removed the keyboard and no results. There's no IDE connected. Should I connect a HD?

                Originally posted by lucasdaytona
                did you tried to fill all memory banks?
                According to the manual, it is not necessary to fill all the banks. However, did not try. Will do it.

                Originally posted by lucasdaytona
                also, 256k SIMMs, never seen this!
                I picked them up from a board I found near the trash bin and worked! Hahaha

                Comment


                  #9
                  Originally posted by [UFO] View Post
                  Yes, I removed all the cards, although you can see a video card connected in the pics. Removed the keyboard and no results. There's no IDE connected. Should I connect a HD?
                  No, when diagnosing things like this it's best to strip it down to the bare essentials to isolate the problem. The board should beep and post with nothing but the monitor and power attached. If it's not doing that, the fault is on the board.

                  I'm not sure if faulty RAM would cause a "dead" response. Others might know. If so, it might pay to swap it out.

                  Tez
                  ------------------------------------------------
                  My vintage collection: https://classic-computers.org.nz/collection/
                  My vintage activities blog: https://www.classic-computers.org.nz/blog/
                  Twitter: @classiccomputNZ ; YouTube Videos: (click here)

                  Comment


                    #10
                    Originally posted by tezza View Post
                    I'm not sure if faulty RAM would cause a "dead" response. Others might know. If so, it might pay to swap it out.

                    Tez
                    I have boards that play "dead" with bad or no RAM. What I don't know is if any of them *don't* play "dead" with bad or no RAM.
                    PM me if you're looking for 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

                    Comment


                      #11
                      Is the CPU known-to-be-good? Does the CPU work on another motherboard?

                      Comment


                        #12
                        Originally posted by Pepinno View Post
                        Is the CPU known-to-be-good? Does the CPU work on another motherboard?
                        Yes, it does. Tested with a 486SX-20, a 48SX-33 and a 486DX2-66, which is the one I have now on the board.

                        Comment


                          #13
                          Are all the jumpers correctly set for your exact hardware configuration (cache memory size, CPU type, CPU speed), according to the (no exactly the same) motherboard documentation you posted?

                          I see you have closed pins 1 and 2 for JP4, and the documentation says for it "Jumper information unavailable", so I would try with this jumper open on its three pins.

                          Comment


                            #14
                            So it sounds like you know:
                            1, CPU is good
                            2. PSU is good
                            3. RAM is good

                            Correct?

                            How about the video card?

                            I'd say plug the board into the PSU w/ a cpu installed and the speaker plugged in (with nothing else, no video card or RAM) and turn it on. If you get a ton of beeps or a long continuous beep, then shut it down and plug the RAM in and try it again. Once again if you get a ton of beeps then go ahead and plug the video card in and turn it on.
                            • If it does not beep with the RAM and video card absent then it is most likely a dead board (since we know the cpu is good), but I would check the manual and do a proper BIOS reset and try again, and also double check all the jumper settings on the board.

                            • If it does beep without the RAM installed, but you get no beeps at all when the RAM is installed then it is a problem with the RAM, possibly the configuration; try using 4 identical SIMMs.

                            • If it beeps with the RAM installed and an absent video card; but does not beep or throw out a ton of beeps (basically anything but a single beep) with the RAM and video card installed then it is most likely your video card, try another one.

                            • If you get a single short beep with the RAM and video card installed but no display then I would try another video card and try again.

                            • If all of this yields no beeps at any stage then it is most likely a dead board.

                            Hope this helps.

                            IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
                            IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
                            Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

                            Comment


                              #15
                              Originally posted by Stone View Post
                              I have boards that play "dead" with bad or no RAM. What I don't know is if any of them *don't* play "dead" with bad or no RAM.
                              In my experience having no RAM on a board causes some interesting beeps, I've never seen a board play dead with no or bad RAM.

                              Here is a list of AMI BIOS beep codes for anyone who is interested.

                              IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
                              IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
                              Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

                              Comment

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