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

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.

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

"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.

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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