Pending: Just a few questions about the insides....

Vic the Trader · 12-25-2008

Just a few questions before I start messing with things.

I've heard that the Power Supply delivers full AC Power to the remote power switch in the front. How does this process work?

What is barred wire, and how is it used in the PC?

What are open contacts? I've heard people say there might be open contacts on the back of the switch? How do you tell?

Today's ATX Motherboards retain power even when the switch is off. Is this power in capacitors you don't have to worry about? How does this correlate with working on a computer? (Assuming you are following the A+ method of leaving the computer plugged in.)

Gandalf · 12-25-2008

Welcome to PCHF.

I've heard that the Power Supply delivers full AC Power to the remote power switch in the front. How does this process work?

The AC power runs from the AC input plug through the power switch to the PSU (Power Supply Unit). When you turn off the power to the computer with the power switch, if the AC plug is connected, there is AC at the input to the power switch.

What is barred wire, and how is it used in the PC?

Never heard of barred wire in a computer. Sure you got the spelling correct? Bare wire is wire with the insulation removed.

What are open contacts? I've heard people say there might be open contacts on the back of the switch? How do you tell?

There are open contacts and closed contacts. If you check the resistance of a closed contact, you should get zero resistance. Open contacts should read infinite resistance.

Today's ATX Motherboards retain power even when the switch is off. Is this power in capacitors you don't have to worry about?

Not worrying about capacitor power is an invitation to computer death if not personal death. Never assume a capacitor is safe to handle. A capacitor can build up a charge even if they are just laying on the table.

How does this correlate with working on a computer? (Assuming you are following the A+ method of leaving the computer plugged in.)

Unless you have an instructor present and are under his/she guidance, never leave the computer plugged in when opening the chassis. I've seen A+ techs who didn't know which end of a screwdriver to use. Also, when working inside a computer, ware a connected ground strap. For your safety and that of the computer.

Vic the Trader · 12-28-2008

Thank you kindly for the response, it provides a tremendous amount of clarity at this point.

Originally Posted by Gandalf

The AC power runs from the AC input plug through the power switch to the PSU (Power Supply Unit). When you turn off the power to the computer with the power switch, if the AC plug is connected, there is AC at the input to the power switch.

By power switch I believe you are saying the switch in the front of the computer (i.e. off/on), and by AC Input Plug, the plug in the back which receives AC electricity from the wall.

So electricity runs from that plug in the back, which is right 'on top of' the power supply, down to the front of the computer, and the power supply does not receive electricity to 'power up' without the power first going through the switch in the front, that of which remains in the hands of outside activation. Seems simple enough. Does the AC current coming from the wall go through the power supply at all before it reaches the switch? I ask this because most plugs are right on top of the power supply.

Also.

Basically, if I am working with the computer unplugged (which seems the more sensible option), as long as I ground myself, and don't **** around with the power supply, I should be safe from any electrical damage to the hardware or electrical damage to myself?

Originally Posted by Gandalf

Never heard of barred wire in a computer. Sure you got the spelling correct? Bare wire is wire with the insulation removed.

There are open contacts and closed contacts. If you check the resistance of a closed contact, you should get zero resistance. Open contacts should read infinite resistance.

Normally, a PC shouldn't have any bare wire or open contacts, right?

Gandalf · 12-28-2008

Originally Posted by Vic the Trader

Does the AC current coming from the wall go through the power supply at all before it reaches the switch? I ask this because most plugs are right on top of the power supply.

If the computer has an on/off switch (some may not), the switch should control 100% of the AC before being routed to the PSU. Having said that, what if the AC switch is broken (shorted)? In other words, all the AC on the input side is always on the output side. You think the power is off and then suddenly POW. You've got 120 volts (or in some countries 220 volts) running through you to ground. That can make for a very bad day. That is why we say remove the AC plug from the computer. If the plug is disconnected, then the only electrical concern is from the capacitor.

NOTE: NEVER open up a monitor. A shock from a capacitor in an old style monitor can kill. Leave that to the professionals.

Basically, if I am working with the computer unplugged (which seems the more sensible option), as long as I ground myself, and don't **** around with the power supply, I should be safe from any electrical damage to the hardware or electrical damage to myself?

That is a fair statement. However, electricity is like an unloaded gun. It's the empty guns that kill people. As with guns, always have respect for electricity.

Normally, a PC shouldn't have any bare wire or open contacts, right?

Yes and no. If you look at a computer circuitboard, you will see silver lines running from component to component. These are usually exposed. However, they should only be carrying 5 or 12 volts. Touching this circuits will usually cause more damage to your computer than to you.

Lastly, take a look at this ...

Electric Blanket Shock - Video

Gandalf · 01-15-2009

Are you still in need of assistance?

12-25-2008	#1
Vic the Trader Bronze Member Join Date: Dec 2008 Posts: 16 PC Experience: PC Illiterate	Just a few questions about the insides.... Just a few questions before I start messing with things. I've heard that the Power Supply delivers full AC Power to the remote power switch in the front. How does this process work? What is barred wire, and how is it used in the PC? What are open contacts? I've heard people say there might be open contacts on the back of the switch? How do you tell? Today's ATX Motherboards retain power even when the switch is off. Is this power in capacitors you don't have to worry about? How does this correlate with working on a computer? (Assuming you are following the A+ method of leaving the computer plugged in.)

12-25-2008	#2
Gandalf Elite Member Join Date: Apr 2007 Location: California, USA Posts: 4,386 PC Experience: PC Guru	Re: Just a few questions about the insides.... Welcome to PCHF. I've heard that the Power Supply delivers full AC Power to the remote power switch in the front. How does this process work? The AC power runs from the AC input plug through the power switch to the PSU (Power Supply Unit). When you turn off the power to the computer with the power switch, if the AC plug is connected, there is AC at the input to the power switch. What is barred wire, and how is it used in the PC? Never heard of barred wire in a computer. Sure you got the spelling correct? Bare wire is wire with the insulation removed. What are open contacts? I've heard people say there might be open contacts on the back of the switch? How do you tell? There are open contacts and closed contacts. If you check the resistance of a closed contact, you should get zero resistance. Open contacts should read infinite resistance. Today's ATX Motherboards retain power even when the switch is off. Is this power in capacitors you don't have to worry about? Not worrying about capacitor power is an invitation to computer death if not personal death. Never assume a capacitor is safe to handle. A capacitor can build up a charge even if they are just laying on the table. How does this correlate with working on a computer? (Assuming you are following the A+ method of leaving the computer plugged in.) Unless you have an instructor present and are under his/she guidance, never leave the computer plugged in when opening the chassis. I've seen A+ techs who didn't know which end of a screwdriver to use. Also, when working inside a computer, ware a connected ground strap. For your safety and that of the computer. Comments on this post driver_ian agrees: very well described __________________ Klaatu Barada Nikto < Pre-Work ><CPUID>< SFC >< AV Scan >< BSOD >< Belarc ><How-To Geek> Join the PC Help Forum WCG Team and fight cancer with us!

12-28-2008	#3
Vic the Trader Bronze Member Join Date: Dec 2008 Posts: 16 PC Experience: PC Illiterate	Re: Just a few questions about the insides.... Thank you kindly for the response, it provides a tremendous amount of clarity at this point. Originally Posted by Gandalf The AC power runs from the AC input plug through the power switch to the PSU (Power Supply Unit). When you turn off the power to the computer with the power switch, if the AC plug is connected, there is AC at the input to the power switch. By power switch I believe you are saying the switch in the front of the computer (i.e. off/on), and by AC Input Plug, the plug in the back which receives AC electricity from the wall. So electricity runs from that plug in the back, which is right 'on top of' the power supply, down to the front of the computer, and the power supply does not receive electricity to 'power up' without the power first going through the switch in the front, that of which remains in the hands of outside activation. Seems simple enough. Does the AC current coming from the wall go through the power supply at all before it reaches the switch? I ask this because most plugs are right on top of the power supply. Also. Basically, if I am working with the computer unplugged (which seems the more sensible option), as long as I ground myself, and don't ** around with the power supply, I should be safe from any electrical damage to the hardware or electrical damage to myself? Originally Posted by Gandalf Never heard of barred wire in a computer. Sure you got the spelling correct? Bare** wire is wire with the insulation removed. There are open contacts and closed contacts. If you check the resistance of a closed contact, you should get zero resistance. Open contacts should read infinite resistance. Normally, a PC shouldn't have any bare wire or open contacts, right?

12-28-2008	#4
Gandalf Elite Member Join Date: Apr 2007 Location: California, USA Posts: 4,386 PC Experience: PC Guru	Re: Just a few questions about the insides.... Originally Posted by Vic the Trader Does the AC current coming from the wall go through the power supply at all before it reaches the switch? I ask this because most plugs are right on top of the power supply. If the computer has an on/off switch (some may not), the switch should control 100% of the AC before being routed to the PSU. Having said that, what if the AC switch is broken (shorted)? In other words, all the AC on the input side is always on the output side. You think the power is off and then suddenly POW. You've got 120 volts (or in some countries 220 volts) running through you to ground. That can make for a very bad day. That is why we say remove the AC plug from the computer. If the plug is disconnected, then the only electrical concern is from the capacitor. NOTE: NEVER open up a monitor. A shock from a capacitor in an old style monitor can kill. Leave that to the professionals. Basically, if I am working with the computer unplugged (which seems the more sensible option), as long as I ground myself, and don't ** around with the power supply, I should be safe from any electrical damage to the hardware or electrical damage to myself? That is a fair statement. However, electricity is like an unloaded gun. It's the empty guns that kill people. As with guns, always have respect for electricity. Normally, a PC shouldn't have any bare wire or open contacts, right? Yes and no. If you look at a computer circuitboard, you will see silver lines running from component to component. These are usually exposed. However, they should only be carrying 5 or 12 volts. Touching this circuits will usually cause more damage to your computer than to you. Lastly, take a look at this ... Electric Blanket Shock - Video __________________ Klaatu Barada Nikto < Pre-Work ><CPUID>< SFC >< AV Scan >< BSOD >< Belarc ><How-To Geek> Join the PC Help Forum WCG Team and fight cancer with us!**

01-15-2009	#5
Gandalf Elite Member Join Date: Apr 2007 Location: California, USA Posts: 4,386 PC Experience: PC Guru	Re: Just a few questions about the insides.... Are you still in need of assistance? __________________ Klaatu Barada Nikto < Pre-Work ><CPUID>< SFC >< AV Scan >< BSOD >< Belarc ><How-To Geek> Join the PC Help Forum WCG Team and fight cancer with us!

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