Using a PC Post Card Tester • 1 Shut Down the Computer and Unplug the Computer from Its Power Source

Using a PC Post Card Tester • 1 Shut down the computer and unplug the computer from its power source. Press the power button again to discharge any remaining power for safety. • 2 Remove the side of the computer and insert the PC post card into a free compatible upgrade slot. PC post cards can be bought to support most types of upgrade slots. • 3 Power on the system but be careful if you do not replace the side. As the computer attempts to boot, the PC post card will try to analyze the problem. • 4 Read the code that is output by the PC post card. Most PC post cards will beep or blink when they are done diagnosing the system. • 5 Compare the output code with the card's manual. Each code is specific to a problem. Once the problem is diagnosed, power off the computer, remove the card and repair the problem. The most common method for testing motherboards is via a speaker, it plugs in right next to your power switch, reset switch, power led connections on your motherboard. If a motherboard is turning on but has errors, you'll hear a beep code. You can then relate that beep code to a chart that will tell you the problem. Whenever you power on your computer, the ROM BIOS runs a diagnostic test of the hardware, called the Power On Self Test (POST). Each stage of testing generates a two-digit hex code. By tracking these codes, you can view a progress report of the boot-up process and diagnose computer problems. By monitoring POST codes using a POST diagnostic card, which plugs into a machine's ISA or PCI port, you can troubleshoot a computer right on the bench, without needing to hook up a monitor, keyboard, or even a disk drive. These cards allow you to make quick work of fixing components and avoid the usual time-consuming method of swapping them out one at a time and retesting. In this Daily Feature, I'll examine how you can use POST diagnostic cards to quickly gather information when troubleshooting a system failure. POST codes vs. BIOS beep codes You may already be familiar with BIOS beep codes (if not, see my previous article"Deciphering BIOS beep codes"). Beep codes use audible signals to alert users to computer problems—an especially useful feature if a hardware failure occurs before the video card is initialized. While some sets of beep codes, such as those generated by the latest Phoenix BIOSs, can provide extensive troubleshooting information, others are less revealing. There may be only 10 beep codes—a tiny subset of the up to 255 two-digit POST codes that can be displayed right on a POST diagnostic card, via digital readouts (Figure A). Figure A This POST diagnostic card, called POSTmortem, plugs into an ISA port. In addition to digital readouts, the POSTmortem also includes four LEDs to diagnose power-supply voltage problems. POST card quick facts POST codes are most often sent to port 80h, although some manufacturers use different ports. Compaq, for example, uses port 84h. POST cards either automatically detect the port or contain jumpers for setting it manually. In addition to providing digital readouts of POST codes, these cards typically include LEDs for troubleshooting power-supply voltages. For example, the POSTmortem ISA card pictured above contains four LEDs for testing +5V, +12V, -12V, and -5V power supplies, as well as five contacts for testing these voltages with a probe. For a more complete troubleshooting solution, get an ISA card if possible. (Your motherboard will likely have an ISA legacy port.) Sometimes PCI ports do not show all the available codes, for two reasons. First, ISA busses are initialized before PCIs—the PCI bus will only receive the codes that are generated after it is initialized. Second, ISA busses connect to the South Bridge chip; motherboards with damaged North Bridge chips may not be able to send codes to the PCI bus at all. POST card makers and code sources You can obtain ISA or PCI cards from these manufacturers: Xetal Systems Inc., maker of POSTmortem; Microsystems Development Technologies Inc., maker of Post Code Master; and PC Certify Inc., maker of several models of diagnostic cards. You can find more manufacturers by conducting a Web search. Before using a POST diagnostic card, you'll need a code manual. A good source for this is The BIOS Companion, published by Electrocution Technical Publishers. This comprehensive guide presents a catalog of POST codes of many models. It also includes a manual of many current and legacy BIOS beep codes and a vast description of BIOS settings. It can be purchased online (as a PDF file) for $15 or printed for $45, or as part of a larger set, called The PC Engineer's Reference Book. The Companion is especially useful if your enterprise stocks many brands of recent and older PCs. If you prefer to get your information on the Web, Mr. BIOS (http://www.mrbios.com/techsupport/award/postcodes.htm) is a useful online source. Note, however, that computer makers constantly tinker with their BIOSs, so check with your manufacturer for the latest specs to be sure your POST codes are accurate. POST card usage As simple as POST cards are to use, they do require some care. Not all models, the POSTmortem included, have protection circuits built in. Therefore, be careful not to install these cards in reverse or upside down. Doing so could burn out the card. A marker shows which way to orient the card. After you plug in the card, power up the machine and follow the progress of the POST test (Figure B). Figure B The POSTmortem card is in place among the components of a legacy Compaq Presario tower. The code you'll see is sent to the card just prior to the start of each test. In Figure B, the code displayed (53) indicates the start of a video display ROM test. The four lit LEDs indicate normal power from the power supply. Should the computer fail during the POST, the failing test number will be the last one displayed. Consider the failed test as only a possible indicator of the real problem at hand—another component may, in fact, be the culprit. For example, a failed memory test could indicate a badly seated chip or a motherboard problem. What POST codes tell you Table A illustrates the type of information you can derive from POST codes. The listing is a sampling of some diagnostic tests run by current (post-1995) American Megatrends Inc. (AMI)BIOSs. These BIOSs are used by many computer makers and are included in off-the-shelf motherboards. Click here for a complete manual of AMIBIOS POST codes. Table A: AMIBIOS POST codes (sample selection) POST time As Table A suggests, POST codes can give detailed information useful for diagnosing computer problems. More informative than many sets of BIOS beep codes, POST codes are a solid diagnostic tool that can save the technician time in comparison to the standard method of swapping out suspected faulty parts. A.)GENERAL TESTING TIPS. Before you begin, download a few of our Diagnostic Software Tools to pinpoint possible problem areas in your PC. Ideally, troubleshooting is best accomplished with duplicate parts from a used computer enabling "test" swapping of peripheral devices/cards/chips/cables. In general, it is best to troubleshoot on systems that have been leaned-out. Remove unnecessary peripherals (soundcard, modem, harddisk, etc.) to check the unworking device in as much isolation as possible. Also, when swapping devices, don't forget the power supply. Power incompetency (watts and volts) can cause intermittent problems at all levels, but especially with UARTS and HD's. Inspect the motherboard for loose components. A loose or missing CPU, BIOS chip, Crystal Oscillator, or Chipset chip will cause the motherboard not to function. Also check for loose or missing jumper caps, missing or loose memory chips (cache and SIMM's or DIMM's). To possibly save you hours of frustration i'll mention this here, check the BIOS Setup settings. 60% of the time this is the cause of many system failures. A quick fix is to restore the BIOS Defaults. Next, eliminate the possibility of interference by a bad or improperly set up I/O card by removing all cards except the video adapter. The system should at least power up and wait for a drive time-out. Insert the cards back into the system one at a time until the problem happens again. When the system does nothing, the problem will be with the last expansion card that was put in. B.)RESETTING CMOS. Did you recently 'flash' your computers BIOS, and needed to change a jumper to do so? Perhaps you left the jumper in the 'flash' position which could cause the CMOS to be erased. If you require the CMOS Reset and don't have the proper jumper settings try these methods: Our Help Desk receives so many requests on Clearing BIOS/CMOS Passwords that we've put together a standard text outlining the various solutions. C.)NO POWER. Switching power supplies (the most common used PC's), cannot be adequately field-tested with V/OHM meters. Remember: for most switching power supplies to work, a FLOPPY and at least 1 meg of memory must be present on the motherboard. If the necessary components are present on the motherboard and there is no power: 1) check the power cable to the wall and that the wall socket is working.

Load more