Solve : What kills the -5 Volt on a Power Supply??

1.	Solve : What kills the -5 Volt on a Power Supply??
Answer» Something in my system knocked out the -5 volt on my power supply. I replaced the supply with a new 850v Antec, within 15 seconds my system killed it, again the tester showed only the -5 volt line was out. Does anyone know what runs off of that line??? THANKS!more info! what is your systems hardware?System: MSI K9A2 mainboard AMD Phenum 9500 CPU 8 gig Corsair Dominator 1066 RAM single ATI graphics card, I forget which one (all other slots are empty) 1 WD Raptor 150 GB SATA drive, 3 WD 640GB SATA drives 2 LG SATA CD/DVD drives Vista 64 BIT ultimateThe VRM runs off of the -5VDC ( Voltage Regulation Module ). It generally takes the -5 feed and regulates it to a lower voltage with higher amperage and capacitor ( power cap ) cushion ( series of Caps near CPU ) to get rid of any ripple ( noise ) and varaibility from the switching power supply. The VRM feeds the CPU and GPU if you have integrated video on this motherboard. The motherboard also uses the -5 for the soft-power ( power SWITCH ), and the BUS also has a -5 and +5 feed. I'd take a meter to your pins for ground and -5 and measure the ohms. If it reads less than 200 ohms, I'd say you got yourself a problem... 0 ohms is a dead short, and anything less than 50 ohms is likely a fried component shorting to ground ( not a dead short, but a semi-conductive almost dead short.) ** Caps can fake a short as well.... If you measure it with a digital meter and it starts at like 300 ohms and starts decreasing in value over a MATTER of seconds it is caps charging from the power emitted by the meter. If you measure and you get a quick value rhat holds and doesnt change rapidly, thats another sign of a problem as for all healthy power inputs should SHOW a capacitor climb ( ohms decrease over time as capacitor charges and acts more conductive to the meter as it saturates the electrolyte. Also do you smell anything funny that smells burnt on the MB? You are likely looking at needing a new MB... what lead up to the failure?No smells, the system was only about a month old when the first power supply died, I had no changed anything. The second supply died on the first boot right after post. I guess I will send the MB back for warranty replacement.Quote If it reads less than 200 ohms, I'd say you got yourself a problem... 0 ohms is a dead short, and anything less than 50 ohms is likely a fried component shorting to ground where are you getting this info? Quote ** Caps can fake a short as well.... If you measure it with a digital meter and it starts at like 300 ohms and starts decreasing in value over a matter of seconds it is caps charging from the power emitted by the meter. If you measure and you get a quick value rhat holds and doesnt change rapidly, thats another sign of a problem as for all healthy power inputs should show a capacitor climb ( ohms decrease over time as capacitor charges and acts more conductive to the meter as it saturates the electrolyte. this is completely incorrect. 1. capacitors themselves contain no resistance. there must be a resistor placed in series with a capacitor to limit the amount of current flowing through the circuit. 2. the pure DC ohmic resistance of an electronic circuit is a fixed value and will not increase or decrease in an isolated electrical circuit. it can, however, be changed by adding or subtracting more/less resistors or by using a variable resistor. 3. capacitors do not act like a conductor when fully charged. actually, once a cap is fully charged in a simple RC (Resistor-Capacitor) circuit, no current will flow. 4. the insulator INSIDE of a capacitor is called a dielectric, not an electrolyte.

Answer»

Something in my system knocked out the -5 volt on my power supply. I replaced the supply with a new 850v Antec, within 15 seconds my system killed it, again the tester showed only the -5 volt line was out.

Does anyone know what runs off of that line???

THANKS!more info! what is your systems hardware?System:
MSI K9A2 mainboard
AMD Phenum 9500 CPU
8 gig Corsair Dominator 1066 RAM
single ATI graphics card, I forget which one (all other slots are empty)
1 WD Raptor 150 GB SATA drive, 3 WD 640GB SATA drives
2 LG SATA CD/DVD drives
Vista 64 BIT ultimateThe VRM runs off of the -5VDC ( Voltage Regulation Module ). It generally takes the -5 feed and regulates it to a lower voltage with higher amperage and capacitor ( power cap ) cushion ( series of Caps near CPU ) to get rid of any ripple ( noise ) and varaibility from the switching power supply. The VRM feeds the CPU and GPU if you have integrated video on this motherboard. The motherboard also uses the -5 for the soft-power ( power SWITCH ), and the BUS also has a -5 and +5 feed.

I'd take a meter to your pins for ground and -5 and measure the ohms. If it reads less than 200 ohms, I'd say you got yourself a problem... 0 ohms is a dead short, and anything less than 50 ohms is likely a fried component shorting to ground ( not a dead short, but a semi-conductive almost dead short.)

**** Caps can fake a short as well.... If you measure it with a digital meter and it starts at like 300 ohms and starts decreasing in value over a MATTER of seconds it is caps charging from the power emitted by the meter. If you measure and you get a quick value rhat holds and doesnt change rapidly, thats another sign of a problem as for all healthy power inputs should SHOW a capacitor climb ( ohms decrease over time as capacitor charges and acts more conductive to the meter as it saturates the electrolyte.

Also do you smell anything funny that smells burnt on the MB?

You are likely looking at needing a new MB... what lead up to the failure?No smells, the system was only about a month old when the first power supply died, I had no changed anything. The second supply died on the first boot right after post.

I guess I will send the MB back for warranty replacement.Quote

If it reads less than 200 ohms, I'd say you got yourself a problem... 0 ohms is a dead short, and anything less than 50 ohms is likely a fried component shorting to ground

where are you getting this info?

Quote

**** Caps can fake a short as well.... If you measure it with a digital meter and it starts at like 300 ohms and starts decreasing in value over a matter of seconds it is caps charging from the power emitted by the meter. If you measure and you get a quick value rhat holds and doesnt change rapidly, thats another sign of a problem as for all healthy power inputs should show a capacitor climb ( ohms decrease over time as capacitor charges and acts more conductive to the meter as it saturates the electrolyte.

this is completely incorrect.

1. capacitors themselves contain no resistance. there must be a resistor placed in series with a capacitor to limit the amount of current flowing through the circuit.

2. the pure DC ohmic resistance of an electronic circuit is a fixed value and will not increase or decrease in an isolated electrical circuit. it can, however, be changed by adding or subtracting more/less resistors or by using a variable resistor.

3. capacitors do not act like a conductor when fully charged. actually, once a cap is fully charged in a simple RC (Resistor-Capacitor) circuit, no current will flow.

4. the insulator INSIDE of a capacitor is called a dielectric, not an electrolyte.

Solve : What kills the -5 Volt on a Power Supply??

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