Power switch cable

[sodakotahusker]

My computer will not start up. I suspect it is the power switch. The power supply is fine. It is a Compaq machine. I was told at CompUSA that they can not get just a switch/cable for a machine - that the whole chassis would have to be replaced. This sound ludicrous to me. This particular model is a couple of years old but all of the newer boxes seem to have exactly the same type of chassis and power switch (externally).
I have an old machine lying around. I was wondering if I could cause any harm to my machine to try using that switch/cable on my new malfunctioning machine?
Also - is there any commonality among systems of these power switches? This seems to me to be (but I am exremely ignorant of electronics) the kind of part that should/could be fairly standardized.
Thanks!!

 

[sodakotahusker]

Some more info:
When I say it won't power up - I mean absolutely no sign of any activity. No fan,etc.
The power switch cable in my new machine is red and black. In my old machine it is blue and white. The new machine has plus that holds pairs of cables (yellow and black and green and black) used for LEDs. This connects to what is an 8 pin receptable (2 rows of 4). The old machine has individual plugs for each LED and then a double one for the power switch.
What I think happened is I messed up the power switch by taping something over the external switch (trying to hide the flashing light which kicks in when they machine is placed in standby mode) - which probably kept the switch depressed. The machine was left on for several months. When I had to turn it back on I had to play with the power switch before it finally kicked in. Then it was on for a couple of months until the power went out.

 

[ImpetusEra]

The power supply has a constant voltage flowing through the motherboard and when you depress the power button it sends a signal to switch on the power supply. Your problem could be the power supply, motherboard or switch. If the switch itself is mounted on a pcb with the leds and reset button if it has one then there could be a problem with that whole piece. The switch itself is likely just a spst momentary switch which you could buy at radiosahck with pocket change. Then it'd be a matter of desoldering the exisiting one and soldering in the new one. It'd help to have a multimeter as you could check the powersupply for the constant voltage, check the switch itself and the wiring for the switch. I've assumed you've tried a different electrical outlet in the house and checked all connections and that the 110/240v switch if it has one is set on 110?

 

[sodakotahusker]

I had the power checked at CompUSA. It is fine.
Yes I tried multiple outlets. I actually took the machine to the office as well.
You did not answer my question. Is it safe to just try the swithch from my old computer or could I fry my mother board if I plugged the cable into the wrong pins or if there was something different about the cable?????
Thanks!!!!

 

[ImpetusEra]

A switch is a switch. You'd just want to make sure it is a momentary switch. Trace which two wires go from the current switch to the motherboard pins and attach the new one to them.

 

[franklin97355]

sodakotahusker yes you could damage the system by connecting the wrong pins. Have you shorted the correct pins (check the manual) momentarily with a metal object to see if the computer turns on?

 

[ceh4702]

A switch on a PC is just two wires with a push-button that completes the circuit momentarily to tell the power supply to start up. It works kind of like a door-bell. You can start a computer with any kind of push switch. It plugs into two pins on the motherboard and completes a low-voltage circuit. It is called a momentary switch. The circuit is only completed the moment it is pressed down.

You can start a computer with any conductive metal object by touching the correct two pins on the motherboard. It will not hurt the motherboard.

So if the switch is bad, the connector on the motherboard could have become disconnected or the wires could have come loose from the connector or from the mechanical push mechanism. If the switch jams or sticks that causes a problem also. Corrosion can cause a problem also.

Sometimes the power supply part that turns it on quits and it is the power supply that has the problem and not the switch.

You can test the motherboard with a screw driver if you remove the connector and just touch the two pins.

If you do not like my post feel free to point out your opinion or my errors.

 

[ceh4702]

I have used a reset button instead of the on-off switch. Of course many computers dont have a reset switch any more. You just pull out the reset and the power connectors and put the reset into the power connector location. Both work the same way.

If you do not like my post feel free to point out your opinion or my errors.

 

[mainegeek]

sodakotahusker,

Yes damage can occur if connected wrong. Just to clarify things, is this an AT or ATX system? If it is an ATX you may be able to unplug the power switch from the motherboard and plug the reset swith button on to the power button switch headers on the motherboard and use the reset button to power on the system. If your power switch is directly wired to the power supply than you most likely have an AT system.

What make and model is your PC?

 

[sodakotahusker]

Thanks everybody for your input. I am learning lots of cool stuff here.

**
You can start a computer with any conductive metal object by touching the correct two pins on the motherboard. It will not hurt the motherboard.
**
ceh4702, are you saying - I could take something like a screwdriver and touch both pins simultaneously and thus complete the same circuit the switch does?? If I could do damage to the machine by plugging the switch cable into the wrong pins - would I not be subject to the same danger by using a conducter? Or are you saying that there is not danger to the motherboard even if I touch the Incorrect pins?

So if the switch is bad, the connector on the motherboard could have become disconnected or the wires could have come loose from the connector or from the mechanical push mechanism. If the switch jams or sticks that causes a problem also. Corrosion can cause a problem also.
I think I caused the switch to either jam or stick by applying tape to the chassis which could have forced the switch into a perpetually on state. Does this seem feasible?

No reset button on this machine.

What is the significance of the color coding on the cables or this just an arbitrary choice of colors used by the manufacturer.

 

[sodakotahusker]

I have a Compaq Presario SR1050NX

 

[dglienna]

I have a monitor that has a button that had become stuck. I just played around with it for 5 minutes, and was able to work it loose, letting me turn off the monitor. I was able to turn it back on the next day, but after a few days, I have to go thru the same thing again. Take the cover off, and see if you can find out where the button pushes the switch. Maybe the switch got pushed out of range?

David

 

[edfair]

That is what you were told. Techs us screwdriver blades all the time. There isn't anything on a current board that can get hurt.
If the switch from the old machine has 2 wires and a two position molex connector you can use it. Worst case is that it may not change anything since there is circuitry on the board that may have gone bad. Can also be corrosion on the header pins, so reseating it 10 to 12 times won't hurt.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[sodakotahusker]

I tried the screwdriver trick and nothing. So I had a tech come over and take a look. Turned out that the power supply was the problem - despite the fact it tested good at CompUSA. I'm up and running again. Thanks everyone for your input.