Pc Resets after a while. Where to look for the Probelm?

[Shahriar]

Hi
I am trying to repair Some ATX power Supplies.but some of them do not have ordinary faults. Most of them are in these two categories.

1- The computer assembler told me that with this bad PS, computer is working well but after a while (i.e. 10 Minutes or more) it will resets. but when they have replaced the ATX power supply, the problem was solved. Where should I look for this problem in ATX?

2- Some ATX power supplies will cause the mother board to fail. I was wondered to hear this because of the Over Voltage Protection circuit in ATXs, but I think maybe the Factory has removed those circuits. My question: Is it possible such thing in case of a OverVoltage protection circuit?

3- When I repaired an ATX, how can I test whether Over Voltage protection (OVP) circuit works to prevent MotherBoard Failing?

ThanX in advance
Shahriar

[mvs sarma]

hai shahriar

generally components with high current  might cause dry solders . first check these.
In smps you find that the elctrolytic caps give way by drying up after some time

if you coud replace as a set  the smps should work.

also see that the Fan in the smps is up and running.

sarma

[ante]

Hi Shahriar,

I don’t know what a new ATX PSU costs in your part of the world but where I live they are very cheap, almost no one repair them and in doing so jeopardizeing the life of the computer.
As you put it “Sometimes, Shit Happens!” ! ;D
Perhaps you are doing this for educational purposes? ;)

[Shahriar]

Dear mvs sarma

Thank you very much i will check it out. BTW, don't you have any Idea about Over Voltage protection?

Dear Ante.
You are right, maybe many of them don't worth to repair, but many of them has just a bad diode bridge or a blow up cap. and repairing of them takes about 20 minutes.  8)

thanX
Shahriar

[mvs sarma]

Hai Shahriar

overvoltage__

Input-- you have a very large window for input voltage. perhaps you may use an UPS like APC at the input and it has built-in stabilization.

output - alrady design looks after. it is some times seen that there are some ZENORS ACROSS THE OUTPUT VOLTAGES SO THAT IN CASE OF FAILURE OF CONTROL LOOP, THE zENOR LIMITS-- BUT HOW AND HOW LONG  -- A QUESTION MARK.

SARMA