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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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low voltage psu
greetings!!!
can u pls help me point out the trouble in the atx psu i am trying to repair. it powers up but its voltage is lower than its specifications. yellow wires- (only +7.5 volts, should be +12v, red wires - only 2 volts, should be +5 v). what could be the problem and where do i start? thanks in advance, ian |
#2
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yhan wrote:
greetings!!! can u pls help me point out the trouble in the atx psu i am trying to repair. it powers up but its voltage is lower than its specifications. yellow wires- (only +7.5 volts, should be +12v, red wires - only 2 volts, should be +5 v). what could be the problem and where do i start? thanks in advance, ian Hardly worth messing with, but I would first look at the bridge rectifier to see if one of the diodes opened. A low input voltage could account for low output voltage if it would still worked. |
#3
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I would check the electrolytic capacitors within the power supply. Use
an ESR meter for this, if available. Also look for capacitors where the tops have bulged up. They are bad. John |
#4
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"yhan" writes:
can u pls help me point out the trouble in the atx psu i am trying to repair. it powers up but its voltage is lower than its specifications. yellow wires- (only +7.5 volts, should be +12v, red wires - only 2 volts, should be +5 v). what could be the problem and where do i start? Under what conditions? In the PC or on the bench? Does it have a load? Is the 115/230 VAC switch set correctly? Did the problem happen on its own or did someone just give you the power supply? Etc. --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#5
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how about if the atx psu does not turn on when the green wire-black
wire is shorted? should i direct my troubleshooting on the controller circuit for PS# ON or should i check first the primary side of the PSU? thanks in advance, ian |
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