...Just been looking on a Dell forum and someone has written that if replacing keyboard does not help motherboard needs replacing.
Any suggestions please? Thanks in advance.
You may not have to replace the mobo. It may simply depend how handy you, a friend, or a repair center is.
The PS/2 port often still uses an actual one-time fuse for the +5V output (needed to power the keyboard). In other words, you overload the connector one-time, and it's kaput until the fuse is replaced.
Other motherboards use an auto-resetting "fuse" (phase-change technology) but the problem remains that if it is overloaded, it will not provide power to the keyboard. Even if the problem is corrected, it can take a few minutes for the phase-change device to cool-down enough to reset itself. So, you may not be able to immediately fix the problem, re-power up and expect it to work. You may have to wait a minute or two.
The upper-limit can vary from mobo to mobo, and some of the new keyboards take a lot of power, perhaps more than some mobos can provide before the fuse kicks-out. I know I've seen one mobo PS/2 port limited to 300mA, and I've seen a PS/2 keyboard that required 500mA...so that combination wouldn't work. (as an aside, the USB device standard limits USB devices to pulling a maximum of 500mA from the USB port)
An PS/2 port overload can be caused by a transient, or even mis-alignment while plugging/unplugging the keyboard while power is on (not good to do with PS/2 connection for other reasons, too)
Checking/Replacing the "Fuse"
If you can detect +5V at the PS/2 port pin4, then a "blown" fuse is not your problem. In some cases, an external device may indicate the presence of +5V by lighting an LED(s) even if the device itself is non-functional. Otherwise, you can just measure pin4 for +5V using a volt-meter. If you do not verify the presence of +5V at pin4, then it's time to check the fuse itself.
If you can locate the fuse (on the mobo), it's easy to test with an ohm-meter or continuity tester. The fuse is usually the last component in-line between pin4 (+5V) of the PS/2 port and the rest of the mobo circuitry.
You may be able to easily replace it. You can order small PC-board fuses from electronic supply shops. In some cases, a suitably sized "wire-link" fuse constructed from a single strand from a small-gauge stranded wire may suffice. Even a larger single 32ga. wire-wrap wire may do in a pinch. Whatever you do, make sure it will "blow" at an appropriately safe current level.
Rather than remove the old fuse and try to solder in a new fuse, I have sometimes just soldered the new fuse on top of the old one.
If this is your problem, the repair can take as little as 10 minutes.
edit to add-
a bit of info about alternative phase-change technology "fuses"
edit to add-
a bit more info on the slightly easier task of checking for +5V at the PS/2 port before having to check on the fuse itself
edit to add-
minor clarification on why there is +5V at the PS/2 port (should be last edit...really)
I checked the voltage at Pin 4 and found it to be the required 5 volts. I will try a USB keyboard when I can get one.
It is annoying that manufacturers deviate from standard ATX power pinouts. I could buy a motherboard/CPU/RAM bundle for less than a Dell motherboard.
I read that later Dell computers used standard pinout on some machines and decided to check mine at the same time as I checked the PS2 socket. Pin 18 on standard ATX should be -5 volts DC but the Dell gives no reading for that pin. I guess I cannot use anything other than a Dell motherboard unless I also buy a new PSU.
...I guess I cannot use anything other than a Dell motherboard unless I also buy a new PSU.
Not necessarily. Starting a few years ago, -5V was required less and less in many modern mobo designs.
The bigger problem you're likely to face is physical form-factor requirements of the Dell case's motherboard mounting issues and output port location requirements.
However, you'll likely find your Dell PSU is fairly low-power output as well, and if you change to a half-way decent configuration you'll want a beefier PSU anyway. Again, physical form-factor may turn out to be your biggest problem in fitting a new PSU into the Dell case.
Some OEM cases are more physically compatible with standard hardware than others.
I could buy a motherboard/CPU/RAM bundle for less than a Dell motherboard.
If you're going to replace your mobo, I wouldn't buy another Dell. You would likely have much more flexibility with a board that wasn't specialized for a specific computer model.
However, I don't know your experience level, but you should understand that if you are planning to simply buy a new mobo (whether it's Dell or not), plug in your current hard drive, and expect it to boot-up and work....that probably won't happen.
If your operating system was pre-installed by Dell, then it is highly unlikely that it will work with any other motherboard, including a different model Dell motherboard.
To be able to use a different motherboard, you need a version of the standalone Windows installation media, and of course any special drivers unique to that specific motherboard. Your computer's "Recovery" installation media or partition won't work on a different motherboard either.
Did you try a USB keyboard yet?
By the way, another thing you can try is to boot from a "LiveCD" disc such as "Knoppix" while still using the PS/2 keyboard. That could give some additional insight as to whether this is a hardware or software problem.
Knoppix can boot a large number of hardware configurations. I've often used one to determine whether I'm looking at a hard-drive/OS/software problem, or a motherboard problem. And if by doing so, I find it's a hard-drive or OS problem, Knoppix provides some built-in tools to help recover data, fix files, etc.
I have tried Suse Linux 10.1 live CD and was unable to get beyond the error message at boot up.
I do appreciate the problems regarding fitting motherboard to Dell case. I can buy a case (including psu) and ASRock socket 478 motherboard for about half the cost of new Dell motherboard. I can use processor, RAM, hard drive and DVD drive. The software was preinstalled on the Dell. Please tell me if I am wrong but I understand that as there is a licence for the Windows XP Home Edition that was preinstalled, I can use my Full Installation Windows XP disk to install the operating system (using the key on the side of the Dell) and that would be legal.
I bought a new ATX Midi tower case and a new ASRock socket 478 motherboard and a new CPU heatsink/fan. I carefully removed the hard drive, CD RW drive, processor and memory modules from the Dell computer. I wore an anti-static wrist band at all times.
I installed all the components into the the new case. All components are compatible with the motherboard. I then installed my Windows XP operating system and other software. All was well. I had a functioning computer that was quite fast.
The following day I decided I would like to replace the CD RW that had been in the Dell. I bought a new LiteOn DVD writer and installed it. I happened to discover that one of the screws that fastened the motherboard the the case was loose and that the mother board was not firm on one corner. I could not tighten the screw any more and did not feel I wanted to leave it like that.
I removed the motherboard so that I could replace the brass mounting that would not allow the screw to be fully tightened. I replaced the motherboard and all screws could now be tightened properly and the board was firm. I connected all the cables as before.
When I tried to start the computer it would not boot. No white text on the monitor just a black screen, no flashing cursor and I cannot even press F2 to enter BIOS as I could the day before. The green power light on the front of the computer came on but the one that indicates HDD activity did not as it had the previous day. I checked and rechecked the connections but my computer still does not work. I tried the bootable Windows Xp installation disk to see what happened but there was no reponse. I disconnected the new DVD writer wondering if that had caused a problem but doing so made no difference.
I cannot understand what can have gone wrong. I had a working computer one day and the next day it would not boot. All the time I was working on the computer the power cable was plugged into the wall socket but the power was turned off. I did this (as advised) so that I could earth the case and clip my anti-static wrist band the the case. I wonder if I may have momentarily forgotten to put the wrist band on and touched the motherboard.
...All the time I was working on the computer the power cable was plugged into the wall socket but the power was turned off. I did this (as advised) so that I could earth the case and clip my anti-static wrist band the the case....
When you say the power "was turned off" are you saying a power switch on the PSU itself was switched-off or just that you turned off the computer using the main front panel power button? If you mean the former, then that's good. The latter means possible damage to components.
As for requiring the system's "earth" or ground connection...that is not required, and can in fact be undesirable. The important thing is to ensure you are at the same electrical potential as the system. The absolute minimum is an ESD wrist-strap clipped to the system frame...but that isn't really sufficient, and in fact the system's power cord should be unplugged from AC mains. A better arrangement is using an ESD mat, the system electrically connected to the mat (don't forget that stand-off feet are often non-conductive), and you connected to the mat via an ESD wrist-strap. However, just to keep charges from continually building up and to reduce the risks, quality ESD protection will have a bleeder resistor connection to "earth", usually via the ESD mat. (BTW, a direct (non-resistive) connection to "earth" can actually result in undesirable higher discharge currents and induced currents and voltages propagated, if by accident a non-ESD-safed contact is made.)
Pre-installed v. "Full Installation" Windows
Stephen Bowles said:
...Please tell me if I am wrong but I understand that as there is a licence for the Windows XP Home Edition that was preinstalled, I can use my Full Installation Windows XP disk to install the operating system (using the key on the side of the Dell) and that would be legal.
In general the pre-installed OS machine's license does not cover this. (by the way you phrased this, I'm assuming you didn't already purchase a license associated with the "Full Installation" copy of XP that you have...that it's borrowed or something like that?) The license for a pre-installed OS does NOT transfer to or cover installing another version of the OS. Pre-installed XP does not equal "Full Installation" Windows XP. In fact, the license for any given copy of an OS may be unique and one cannot make any assumptions. For example, people talk about the "XP EULA" as if there is only one, when in fact there are many different XP EULAS out there. There are even multiple different versions of the XP Home EULA, and multiple different versions of the XP Pro EULA, etc. The EULA for an "Academic Edition" from one university will likely be different from an AE EULA from another university. They tend to have their own contracts with Microsoft, which means they tend to have different EULAs...and none of them are transferable to other versions of the OS.
The EULA for one manufacturer's pre-installed copy of the OS will generally not be the same as for another manufacturer's EULA...in fact, the EULAs may even differ from one model of a manufacturer's computer to another model even from the same manufacturer.
Pre-installed versions of Windows, designed to be used on a single specific computer only, are usually modified versions of the full-blown OS. That is why some pre-installed OS don't work when you change certain hardware. Even if the reason for the change is a hardware failure, the license is generally not transferable. In other words, it can be required that another license be purchased for the "new" computer. Similarly, you can't usually take the pre-installed OS disk from one system and put it in another identical system. Even if such a swap is technically possible, it is often not permitted under the license. It depends entirely on each negotiated contract between a manufacturer (or systems integrator, etc) and Microsoft when the manufacturer wants to license/provide an Windows OS with its systems.
edit-apologies for the edits...another day on full pain meds.
edit-better wording on a declared statement
My full version of Windows XP is a legitimate copy and has only been installed on the desktop computer I have been using for about four years.
I thought as both my full version of XP and the preinstalled version on the Dell restore disk were Home Edition I could legally use the full installation disk to install onto another computer using the code on the Dell.
I have read your comments and now believe that as the code on the Dell belongs to the preinstalled Windows XP software on that computer, it would not be legal to install Windows XP on a new computer with the code from the Dell.
As you will see from my other posts, the new computer failed after a short period. I had expected to be able to persuade Microsoft to activate the software on the new computer as the licence for the Dell was legitimate. Having read you comments I now believe that Microsoft would not accept my request so I shall have to buy new software.
A man at the company that sold me the anti static wrist band told me that attaching the cord to the computer case was "no good" unless the case was connected to ground. That is why I had the power cord connected to the power point (wall socket) with the power switch on the power point turned off.
You say the minimum protection required is to attach the wrist strap to the computer case but that the power cord should not be connected.
I also have a bonding plug that fits into a power point. Would it be better to replace the cord on my wrist strap with one that has a press stud that can be connected to the bonding plug?
A basic diagram is included in the referenced article. Note that although the article says items should be grounded, it neglects to mention that the ground should ALWAYS be made through a resistor. Note however that the diagram in the article shows the wrist-strap is properly attached through a resistor R1 to ground, the desk mat is attached through a resistor R2 to ground, and the floor-pad is attached through a resistor R3 to ground. The resistors used are typically in the 10Mohm range, but can vary.
The computer frame should be in contact with the desk mat. That can be achieved via a purpose-made separate clip, or by ensuring the frame (an unpainted/uncoated surface) physically touches the mat. That's why I earlier mentioned to not forget that the stand-off feet act as insulators.
The computer you are working on should NOT be attached directly to ground, and that includes direct grounding via the power-plug. It ideally should be plugged-in to AC mains only when all parts have been properly installed and the case buttoned-up so that parts are no longer directly accessible.
Chairs should be of a type to not build-up static charges, and ideally the user also wears heel-straps, booties, or special ESD shoes.
And again, when I said the wrist strap was the "minimum", that did not indicate it alone is sufficient. It will reduce the injection of ESD into a system or component, but will definitely not eliminate all possible sources of ESD. But many people either can't afford or are unwilling to implement all the required ESD mitigation devices and protocols, and they leave them out at their peril.
That's a smart and good thing to do. I suspect many of the "mysterious" and ultimately unsolved hardware problems people report are due to ESD damage. This includes failed memory sticks, CPUs, disk-drives, or motherboards that were "just working yesterday".
When static charges as low as 30 volts can permanently damage some modern components, it only makes sense to take appropriate ESD precautions. Too many people treat ESD much too casually.
edit to add-
It is very important to remember that ESD damage can be latent. That means an un-noticed ESD "zap" from several months ago can start a semi-conductor break-down that over time degrades and appears as a sudden total device failure today.
This story started with me buying a new motherboard to fit in a new case. I used the processor and memory from an old computer.
The "new" computer failed after a short period. I could not get past the "beeps" to enter the BIOS. I was locked out.
I returned the motherboard to where I bought it. They said they would test it and if it was found to be faulty I would be sent a new on.
I decided I could not wait so bought a new motherboard CPU and memory to install in the new case I had bought. After receiving good advice on this thread about the dangers of ESD I was ultra careful. I bought an ESD mat and wore a wrist strap. The computer was not plugged into the wall socket. Two hours later I had a functioning computer. I installed OS and software. It is the best computer I have ever used. Super fast and excellent graphics.
Today I received a replacement motherboard, as the company I bought it from agreed it was faulty. Where I destroyed it through careless handling or not I will never know. My final questions are as follows:
Is there any risk that the CPU and RAM that I tried on the first motherboard could have caused the damage?
Is it safe for me to try them on the new motherboard?