TROUBLESHOOTING.

BIOS/CMOS

THE BOOT SEQUENCE

CABLING PROBLEMS

IRQ and I/O Address Problems

PRINTER ERRORS

BASIC NETWORK & COMMUNICATIONS

REMOVING COMPONENTS

© 2002 Ferdinand Valiente Home Page. All rights reserved.

The most common problem that occurs when reassembling a computer is that the BIOS is reset.  On many motherboards this is no longer a problem, as they load in a set of bootable settings anyways.  On older boards that don't have this ability, you have to re-install your basic settings for the computer.

The most common problem is lost IDE settings.  This is obvious because your hard drive won't boot.  Go into your BIOS and look under the IDE Settings page.  It should have a setting to state something to the effect of "Re-Initialize IDE Settings".  Basically, you want the motherboard to search for your hard drives.  Once it's done, save and exit the BIOS and the computer should boot.

There are also about 40 more settings in your BIOS that you shouldn't touch.  Stuff lime SDRAM Timing, AGP burst speed, and CPU cycle speed should be left until you have the system working.  If you mess with those settings before you have the computer operational, you may never find the source of your problem.  If you change one of these settings and you don't know how to change it back, you can always choose the Load BIOS Defaults option to restore your BIOS to it's factory state.  (Although you'll probably have to re-search for your IDE properties again.)

See other links to BIOS CMOS MEMORY UPDATES & TIPS, Clearing all Mother board BIOS setup.

DOS Boot Sequence

1. The computer scans for a Master Boot Record on either Drive C: or A:, depending on which drive is present and the order set in the CMOS.
2. The Master Boot Record (MBR) and DOS Boot Record (DBR)  is loaded.  The MBR loads if booting is occurring from a hard drive, and is followed by the DBR.  The DBR only loads if booting is occurring from a floppy.  Once the boot record is loaded, the boot partition is located.  
3. The DBR loads IO.SYS and MSDOS.SYS.  IO.SYS loads CONFIG.SYS.
4. COMMAND.COM loads.  COMMAND.COM then loads AUTOEXEC.BAT.
5. COMMAND.COM displays the command interface.

Windows 3.x Boot Sequence

The Windows 3.x Operating System technically does not boot on it's own.  It uses the DOS boot sequence because it runs from a command inserted in AUTOEXEC.BAT called WIN.COM.  Windows 3.x can NOT run without a prior DOS installation because of it's dependence on DOS.

Windows 9x Boot Sequence

1. The POST is run by the BIOS.
2. All Plug-And-Play devices are configured by the BIOS.
3. The partition table is loaded, and the boot record initiates IO.SYS.  The Real Mode section of the boot begins.
4. MSDOS.SYS initiates any Windows 9x boot paramaters, including Multi-Boot.  
5. If file compression is present, DRVSPACE.BIN loads.
6. SYSTEM.DAT is checked, and when validated loads the registry.
7. The computer is scanned for new hardware.  Any new hardware is identified and the computer looks for drivers for that equipment.
8. If CONFIG.SYS or AUTOEXEC.BAT have any instructions in them, they are initiated by IO.SYS.  Real mode ends and Protected mode begins.
9. WIN.COM loads.  All virtual device drivers and Virtual Memory Drivers are loaded, including SYSTEM.INI and VMM32.VXD.
10. The GUI, Kernel, and User interfaces are loaded.  Internet Explorer begins, and network support is loaded.
11. Any files with a RunOnce registry key are loaded.
12. Any files in the Startup registry key are loaded.

Boot Error Messages

You'll need to know some of the basic boot error messages.  DOS errors are fairly easy to deduce, as Microsoft hadn't realized how useless they could make their messages yet.  When Windows 3.x came around, the messages got longer and less useful.  By the time Windows 95 came around, error messages required a secret decoder ring to figure out.  None the less, you are required to know these basic errors.

Quick Tricks For Diagnosing Boot Errors

There are some easy tricks to remember when diagnosing boot errors in both DOS and Windows.  Here are a few;

1. Most DOS boot errors are directory errors in CONFIG.SYS or AUTOEXEC.BAT.  Always check to make sure you have the correct directory path and that the file name is correct.  Also, make sure the file is present where you're telling the system to look for it.
2. In DOS, use the PATH command to add functionality to the system.  The PATH command allows COMMAND.COM to automatically load commands into the interpreter by simply listing the command in the PATH line.  Adding the Windows directory to PATH can give you Windows setup capability within DOS.
3. Most problems with loading Windows 3.x occur because of swap file problems.  If possible, try to set up a permanent swap file of sufficient size to keep your system running.
4. If you can't load Windows 9x, press F8 when the "Starting Windows 9x" line shows up after the POST.  Choose Step-By-Step Confirmation.  This will ask you before loading any file, and can help you isolate a problem that Windows is not giving you an error for.  (This happens ALL the time.)
5. If you want to see where a Windows 9x boot is failing, check the BOOTLOG.TXT file.  You also can boot in Safe Mode using the same F8 command as #4 to boot the system with minimal drivers and no network support.

OTHER LINKS TO: SETTING UP/STARTING/SHUTTING DOWN
 

With all the cables you've had to run, it's not uncommon to turn on backwards or forget to hook one up.  This includes your power, which can cause all sorts of weird errors if not hooked up correctly.

Here is  a link detailed connection of the PC.

  Here's a quick list of errors and their symptoms;

Another common problem is for the I/O addresses and IRQ settings of individual components to conflict.  This often occurs because of new components being installed or old components being installed in different slots.  This can also occur if you remove the CMOS battery or reset the BIOS to defaults.

If you have a Plug-and-Play BIOS, this is easy to fix.  Simply go to the BIOS, look in PnP settings, and hit PnP Reset.  This will tell the motherboard to re-assign all it's IRQ and I/O addresses, and as long as all your equipment is PnP it will eliminate the problem.

If you don't have a PnP BIOS or all your equipment isn't PnP compatible, it's time to start looking at jumpers.  Try to find two pieces of equipment that are set to the same IRQ or I/O address and change one of them.  

The last common problem is with serial ports.  Often times when you install a modem it's default is to use the same IRQ as COM 2.  If you have COM2 enabled on your motherboard, you'll get a conflict and Windows may crash when you try to use your modem.  Simply disable COM2 (If you're not using it, which you most likely aren't) and this problem goes away.  PnP modems will avoid this problem all together, but PnP didn't really take hold in the modem market until well after it was established everywhere else in the computer.  Older modems can be a pain in the hind quarters, so watch for this problem.

There is a fair amount of information on fixing printer errors that you will see.  Finding printer problems involves a fairly involved process to define and deduce these errors.  Below is a table to explains each step in the process, and why you should perform the steps in that order;

Troubleshooting Network PCs

The first rule of troubleshooting Network PCs is the same as with any computer system; Look for the obvious.  You'd be surprised how many times people kick a switch with their foot or pull a cable out of it's socket and never realize it.  Before you troubleshoot ANY PC, do a quick look to make sure it isn't something simple.  This also gives you time to look at what equipment is in the computer and how it is connected to the network.

If it's a network-specific problem, check to see whether you're connected to the network or not.  This is done by attempting to open a network folder or drive.  If you double-click My Network Places and you see other computers on the network, you know the computer is logged in.  If you don't, you must attempt to find out why.  (We'll cover more on this in a bit)

If the problem is non-network related, you should take a couple steps before attempting to service the PC.  First, back up the files on the PC.  (Again, you should be doing this anyways)  Secondly, examine the network structure before attempting to make changes.  If you remove the cable from a bus or ring topology, you bring down the whole network.  Determine what format of network you're dealing with, and decide your action from there.

If you must disconnect a computer from a Bus or Ring network, try to keep the cable plugged into the NIC.  Although the computer is not functioning on the network, the network doesn't fail.  Star networks don't care, so feel free to unplug them.  (When the computer is turned off of course.)  If you have to take down a network, make sure you tell someone first, and set a realistic time table for how long they will be without network services.

If the trouble with the PC is network related and you can't log on to the network, more skill is required. 

1. Look for kinks, breaks, and folds in the cable leading up to the network.  Broken cables can isolate PC's on a network, and can often lead to a total network failure.

2. Look at the Protocols that have been installed on the PC, and then look at other PC's in the network.  If you're missing a network Protocol, try re-installing it.

3. Make sure the User Account on the computer was logged in to.  If someone hit the Escape (ESC) key instead of typing in the password, the computer won't log on to the network.  Also make sure the user account is present on the server.

4. Try plugging in a different NIC.  A defective NIC can be a pain to troubleshoot, and often won't show in the in the device manager as defective.  

If after those steps you still can't log on, I suggest asking a certified network technician for advice.  They have methods of determining problems quicker than the standard "Hunt and Peck" method, and will say you time and your customers money.  Read up about Frame Types for IPX networks, permissions for NT networks, and other networking issues in our MCSE tutorials for hints as to how to solve networking problems.

A Quick Lesson In TCP/IP

Because the Internet has become so widespread, learning the basics of the TCP/IP protocol is imperative for any computer technician.  Therefore, here is a quick lesson in the Transmission Control Protocol/Internet Protocol.

Terminology

TCP/IP - Transmission Control Protocol/Internet Protocol - The primary protocol used on the Internet.  TCP controls how packets are broken down to be  transmitted on the Internet, and IP states how individual nodes are addressed and re-assembles the packets on the receiving end.  

IP Address - TCP/IP uses a numerical address to distinguish nodes.  This address consists of 4 8-bit numbers separated by decimals.  For example, 123.92.145.17 is a valid IP address.  The first 2 sets of numbers are the network identification portion of the address.  The second 2 sets are the host identification portion.  Computers on a network will share the same network identifier, but must have unique host identifiers.

Domains - A domain is a distinct network in a TCP/IP system.  All nodes in a domain share IP addressing properties and security systems.  They also share a common domain name.  For example, all computers on a network assigned to a specific IP can be found by a simple <name>.com system.  ABS-CBN.com is a domain name, and all computers associated with ABS-CBN.com networks share the same IP network identification and structure.  Domain names are used because they are easier to remember than the IP number.

HTML - Hypertext Markup Language - The basic format used to present information for web browsers on the internet.

HTTP - Hypertext Transfer Protocol - The protocol used to transfer HTML documents on the Internet.

IP Addresses

As we stated before, IP addresses are always 4 sets of 8-bit decimal numbers.  This makes IP addresses 32-bit.  Each 8-bit segment is called an octet, and has a maximum value of 255.   This makes a maximum total number of IP addresses of 4,294,967,296 on the Internet.  Although this may seem like a large number, it is not.  (IPv6 will be released shortly that will deal with this problem.  It has a maximum number of IP addresses in the trillions.)

 IP addresses can be assigned in two different ways.  Static IP addresses are addressed to a node permanently.  Dynamic IP addresses change every time a node logs on to a network.  Static IP addresses are necessary for computer that always must be associated with a single IP address, such as servers.  Dynamic addressing is used for nodes that don't require their IP address to always remain the same, such as workstations.  By mixing Static and Dynamic addressing, you avoid problems with running out of IP addresses while maintaining the structure of the Internet.  Dynamic addresses is performed by a Dynamic Host Control Protocol Server, or DHCP server.

DNS

For large networks, changes in the domain structure can confuse network users.  If a domain switches IP addresses or a new computer is added, these changes must be shown to all the computers on the network.  This is done through a Domain Name Service, or DNS server.  A DNS server keeps track of all the IP addresses on a network, or on the Internet.  When a person types in a domain name to access, the DNS server examines it's files for the location and routes the request to the right area.  This allows changes in the network or the Internet to be noticed by all the computers on the network without having to tell each individual computer.  It also allows you to type in a domain name.

WINS

Windows Internet Naming Service operates the same as DNS, but with a couple differences.  First off, WINS is only functional on Windows networks, and can't be used by UNIX or OS2 systems.  Secondly, it keeps track of Dynamically Assigned IP addresses as well as Static.  This means you can find more computers easier, but only on Microsoft networks.

Network

So the printer looks okay, but it's on this funky connection that doesn't go straight into the computer.  How do you deal with this?  The first thing you MUST be able to do is identify a computer that is on a network, and then understand how to deal with that computer.  (You don't need to know everything about networking, just enough to identify simple problems.)

The easiest way to tell a network computer is the interface.  All network computers have one of three devices installed; A NIC, a modem, or a Wireless NIC.  The first two have cables that attach directly to a card on the motherboard or ISA/PCI bus.  A wireless NIC has an antenna coming from either the Monitor, or a PCMCIA card installed in a slot on the computer.

Once you've identified a computer is on a network, there are several precautions you must take.  The first is to find out what kind of network the computer is on.  Disconnecting a network cable from a Token Ring network or disconnecting a server can bring down the entire network.  Star and Mesh networks can usually have a single computer removed from the system without any problems, but you should try to keep the computer connected unless you know for certain or there is no other way.

Common Network Problems

The most common software problems that occur when dealing with networks are listed in the table below with a couple quick descriptions;

Before You Begin - Make Some Notes

Most experienced technicians skip this step.  As you become more acquainted with a computer, you normally will be able to as well.  The trick is to be able to recognize something that you haven't seen before, and document it so you can duplicate the setup.  Basically, if you don't know what it is, document it before you take it apart.

Removing Adaptor Cards

The first step to disassembly is to remove the adaptor cards.  Most of them simply plug into an ISA, PCI, or AGP slot, and are held in with a single screw rear the rear of the case.  Assuming you've already removed any attached cables, remove the screw and store is safely.  (You have no idea how frustrating searching for screws can be.)  Now pull the card away from the motherboard.  You should pull straight if possible, as it is less destructive to the card.  If you have to wiggle it a bit, try not to pull it too far, as the pin contacts can damage the inside of the ISA or PCI slot.  Don't touch the chips or the circuits if you can avoid it, as this will also do damage to the card.

Put each card inside an anti-static bag as soon as you can.  You won't do any damage to the card right away by leaving it exposed, but every bit of dust and electrical charge it picks up shortens it's life in the long run.

Storage Drives

Next you must remove the hard drives and other drives mounted in the case.  First remove the cables plugged into the back of each device.  Most of the cables are pretty standard, and don't require you to remember exactly what drive they were plugged in to.  We'll deal with that when we re-assemble the computer.  The only exception is older CD-ROM drives that plug into the sound card.  Make sure you make a note of this, because it can be a pain trying to remember it later.

Now you must determine how the drives are held in.  99.44% of the time they are held in by 2, 3, 4, 5, 6, 7, or 8 screws.  (Looking at my main hard drive, it has 1 holding it in right now.......   Bad technician... BAD TECHNICIAN!!!)   If it's not held in by screws, prepare for another screwless case debacle.  You'll have to figure out the right combination of levers and slides that allow you to remove the drive.

Remove all the screws that connect the drives to the metal chassis ONLY.  Don't unscrew the chassis screws that connect to other parts of the chassis unless the case is so poorly designed you have to.  Then slide each drive backwards or forwards until it is free of the computer.  Store your screws with your adaptor card screws, and store the drives in anti-static bags.

Disconnecting Power

Next we're going to separate the power supply from the motherboard.  This comes in two stages.

Stage #1 - Look for the AT or ATX-style power connector.  It is either two-9 pin connectors (AT) or a single 20 pin connector. (ATX)  The ATX connector just needs to be unlatched and pulled off.  The AT connectors might require unlatching and a little force.  Pull them straight up, and then move them forward to pull them off their slides.  (Remember when you go to put them back on that the black wires ALWAYS go beside each other.)

Stage #2 - Look for the connectors that connect the power supply to the pin connectors for the case.  AT cases will most often connect straight from the power supply to the front panel on the case.  ATX cases do this through the motherboard.  Pulling these connectors straight up will remove them, and you might as well disconnect all the other wires from the case to the motherboard at the same time.

BUT WAIT!!!!  Notice how there's between 5 and 8 connections there?  Did you happen to mark them down?  Each motherboard has it's own pin layout for how those connectors work.  Some work in both directions, meaning you can't put a cable on backwards.  Others will stop the system from booting when put on backwards.  Mark the position AND polarity of each connection before you even think of pulling it off.  

And if you pulled them off before you read this paragraph, you have just learned a valuable lesson.  ALWAYS read the entire instruction set before attempting to start a project.  It's better to find a problem exists before you start working on a project than to be half-done and stuck.  Hopefully you didn't yank any wires, and hopefully you'll think twice before you ever do again.

Removing The Motherboard

Now comes the fun part.  If you're lucky, you can remove two or three screws now and one side of the case with the motherboard attached will come loose.  If not, look again...  95% of cases do this.  It's just finding out how that's the problem.  The whole metal plate should come out of the case with the motherboard attached.  If you unscrew the plate and it doesn't come loose, make sure you have ALL the adaptor cards and cables removed.

Once you have the motherboard on the chassis in front of you, look for the screws that attach it.  Normally there will be a minimum of 3 and a maximum of 7.  Unscrew each connection.  Make sure you save the screws AND the washers.  lift the motherboard off, and examine how it was connected to the plate.  Normally standoffs of a plastic or metal variety are used.  If they are metal, look for more washers.  

If you plan on re-using the case, make sure you store the standoffs, screws, and washers all in a safe place.  You'll need them again later.

Cleaning Up

Place your motherboard on top of an anti-static bag on top of a non-conductive surface.  You'll notice there are RAM SIMMs/DIMMs still attached, as well as the CPU and fan/heat sink.  Let's work on the RAM first.

If you have 30 or 72 pin SIMMs installed, you'll notice little metal tabs on either side of the SIMM.  Pull then back, and push the SIMM forward.  The SIMM will come out.  DIMM's use levers on either side of the DIMM as well.  Push the lever away from the DIMM and the DIMM will come loose.  Store each SIMM and/or DIMM in it's own anti-static bag.

Next, examine the latching mechanism for the fan/heat sink.  Normally it's hooked on, and the hook merely has to be pushed down to release the fan and heat sink.  ZIF socketed processors only need the ZIF socket level released to loosen the processor.  PGA requires you to pull the chip out like an adaptor card.  Personally, I'd leave the chip in unless you A) need the chip somewhere else B) need to put a new chip in, or C) have a death wish.  All those little pins on the bottom have to be pointing straight down.  Ever tried straightening one of those damn things?  It's not fun.  So keep the chip on the motherboard as long as you can, or if you can store it safely.

Be careful with processors.  If you take them out too quickly, they can be quite hot.  If your 200 Degree processor contacts your 80 degree fingers, the next contact will probably be the processor and the floor.  I've dropped a processor before.  They crack real nice.  And all those tiny wires in there won't work ever again, because you can't fix a processor.

Finally, place all your extra items lying around into proper packaging.  Components go in anti-static bags, tools back in your tool box, and screws and washers store nicely in sandwich bags with zip lock tops.  Anything you loose will make it that much harder to re-assemble next week.

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Acknowledgements

Portions of this data are based in part on the work of Ferdinand Valiente and in the help of Yahoo! GeoCities - Your Home on the Web®. Copyright © 2002 Ferdinand Valiente Home Page. All rights reserved.

This product includes software developed by the other company and its contributors.

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©2002 Ferdinand Valiente Home Page All rights reserved.