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Why does my disassembled Pentium computer does not power up at all?

G

'Georgy Papantoniou'

Experienced Member
Joined
Nov 25, 2012
Messages
59
Location
Nicosia, Cyprus, Cyprus
I am talking for a different computer here, not the one on the other post. It is Pentium 4 too.

When I received this computer I decided to disassemble it for parts, since it was no use to me at the time (even if it was fully functional).
I did not try to power it up since 4 years ago, before it was disassembled.

The only parts that were removed at the time were the floppy drive and the hard disk which I gave away. Everything else is in place, the motherboard intact with all power supply cables, RAM, processor in place. When I plug it in though and push the start button nothing happens, even if I connect a PATA hard drive I have on the motherboard. What do you suspect is the reason? I would be glad if it reached the BIOS at least.
 
Nothing at all? Any fans spin or anything? First suspect is always the power supply but could also be a motherboard connection disconnected. Even sitting turned off the capacitors can dry and blow so you might check for those on the motherboard or power supply too.
 
That and make sure it's set for the correct voltage on the back of the power supply. Not that it gets switched ever without malicious intent but it can throw folks off too.
 
And since you say it's disassembled, check the power switch and other connectors on the motherboard. Make sure all connections to the motherboard are secure.

Connecting hard drives or other peripherals won't make a difference.
 
All connectors to the motherboard are secure
The power supply has no on and off switch
Not even a fan works in the system
The PSU is unscrewed, and it hangs a bit loose in the case (not much)

What can be the problem? I checked the machine again and no component other than what I told you is missing or damaged
 
The only obvious element that has not been checked is the fuse inside the power supply. If the power supply has its own fan which is not running, I would focus on the power supply.

Also, since it is a P4 system, is it one of those screwy RAMBUS RDRAM socket equipped system? If you removed RAM without installing the special spacer in its place, the system won't do anything.
 
There are really cheap ATX power supply testers out there that you could test with. There's a trick to do it with a voltmeter but you have to short two connections on the motherboard connection to get it to power on.
 
This is the model of my PSU fsp250-60pna. In the picture you can see a red thing above the fuse. Do you know what it is? Maybe its a strange switch? The fuse seems OK in my PSU, and I screwed it back to the case, the cable is the same I used when I last powered it up

What can be wrong?
 
I had it on 230V, and I tried both voltages, no difference.

I saw something I did not notice before that alarmed me. At the back of my case there is a "button" resembling a naked power button. The cables attached to it are hanging loose, and they are connected nowhere. I think this is the reason that it does not power up, but I have no idea as of where the cables belong.

Any ideas what this button can be?
 
Do you have the ability to take pictures of the cabling? There used to be power buttons attached to the power supply that you would put behind the computer cases power button but I haven't seen that done for quite some time. Now adays it powers on by being plugged in and the power button really just shorts two connections from the motherboard power jumpers and on the atx connection on the motherboard. The status connections and power connections, etc are from the case to the motherboard though not really attached to the power supply.
 
If it worked before disassembly, then I would be pretty sure the problem is just some wrong connection. The easiest to get wrong are the headers for the connectors to the "power" and "reset" buttons on the front of the case. If the PWR front panel connector is not on the correct pins the power supply will not switch on. I would also check whether anything has come loose where those cables connect to the switches on the case front panel.

Rick
 
I finally managed to find where the cable belongs to. It is a two pin cable. When I tried to start the machine though, the PSU made a strange sound, and then all my attempts to start again the machine failed. Do you think that I should give up on this?
 
It does seem that your PSU may have failed. It is usually not too hard to find a cheap second-hand ATX PSU from a local repair shop, as people often upgrade to higher-power models. I recommend trying a cheap replacement because it is possible that there is a serious short circuit on your motherboard that might have blown the fuse inside the PSU (that noise you heard) and I would not risk another expensive PSU without checking that.

But first you should check whether your PSU is really dead or not. Take the PSU out of the case, use a paperclip or a short piece of bent wire to short the GREEN wire (pin 14) to any of the BLACK wires, then plug it in and switch it on. If the fan starts up, then you should if possible check the voltages according the pin diagram that you can find easily by googling "ATX PSU PINOUT". If you don't have a multimeter, I'm sure you can get very cheap ones for less than $10 locally. If the PSU is OK, then your problem is with the motherboard and may be too complicated to resolve.

Rick
 
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