Thanks for all your input, at last I decided to change item by item. When I changed the 2 npn transistor, the psu works. I measured both in diode mode, they are normal..
so anyone can tell what is a better method to test npn transistor or to buy a tester ?
as mention from start I am more keen to explore what I do not know. Whether this pc got repaired make no difference to me.
anikin73
Senior Member
Last Activity: 09-21-2024, 05:34 AM
Joined: 03-17-2022
Location: singapore
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For gigabyte mono, my first guess is , swap with the spare bios first… since got beep means the code got run…Leave a comment:
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tell you a good news...i had repaired this model many times.....especially no startup. this board easy for broken /burnt copper traces.
1) try to trace whether IO to PSON is connected ?
2) check IO PSON is brought to 0V when u switch on.
3) check the standby voltage are no before you switch on....Leave a comment:
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I tried but it is not this issue. opto couple was not activated at all. even i lift the opto couple up also there is no response from psu. I actually did tried this in the past. the problem is more strange than any other psu that i had encounter.
any other have some idea how to trouble shoot this particular chip ?...Leave a comment:
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FPO will on u5 opto coupler and then on 2907 Q7, then VCC 16 V will appear. It has VCC. So it is not FPO. I will check on u7 as u suggested. Thanks for the Input....Last edited by anikin73; 07-27-2024, 08:50 PM.Leave a comment:
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Model as shown below. But is 500w. I suppose it is the same design since only 100w difference.
1) VCC has 16 V . It’s from the opto coupler. Which is activated by pson green wire.
2) no output Pwm to the 2222A and 2907 transistors.
3) transistors I measure are fine. All components seems fine after measurements.
4) I recently repaired psu using same chip. Gamemax 500w to 800w also use the same chip.
5 ) so it must be other pins unable to fulfill the requirements and hence no start up.
6) it is a low voltage 500w and hence not expensive and hence i did not waste...Last edited by anikin73; 07-27-2024, 08:10 AM.Leave a comment:
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The schematics is not the actual one. But from another psu. So may not directly apply. But very similar.
VCC have 16 v. But not Pwm to the main mosfet. The mosfet seems ok . The chip is the 9 pin type....Last edited by anikin73; 07-27-2024, 06:48 AM.Leave a comment:
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Short green line and the opto couple will cause vcc to have 16v. This part is normal. No square wave from chip as I measure .Leave a comment:
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Usually like that is very hard to repair one. Have u tried to use a gpu to boot up ..in the event u are using the cpu igpu.
the code might be running but u do not know.
other than that, pch is gone.
move on.Leave a comment:
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the actual picture of the components as follow. This PSU seems so new that i suspect easy job but ..........
Leave a comment:
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To add, the pwm to the mosfet has 2 transistors Kn 222A and Kn 2907 A . I had checked and all normal.
Pin 9 IAC i had check and add addtional resistors but still no start at all. [ATTACH=JSON]{"data-align":"none","data-size":"thumb","data-attachmentid":3304378}[/ATTACH] I am curious what mistake i made. I check through all components but seems nothing is spoilt. Any idea will be appreciated.To add, the pwm to the mosfet has 2 transistors Kn 222A and Kn 2907 A . I had checked and all normal.
Pin 9 IAC i had check and add...Leave a comment:
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Cooler Master 500W atx psu repair. Total cannot start at all
I am attempting to repair this. Circuit is quite simple, but i a quite stuck at it for a long time. so today i try to ask for new ideas. my challenge is to under stand what mistake i made. I had repaired not lesson than 50 pcs of various brands ATX psu . main pwm chip is Cm 6805 Sip 9 .
5VSB is fine. When I short Pson, totally nothing happen. I check , the Cm 6805 VCC pin2 did have 16v, But totally nothing happen. I changed to a good chip from another good PSU. Same thing.
What other pin should I check such that it will result in no start up at all ?
[A... -
OK let me give u afew pointers to help- check whether boot up cycle complete , all voltage appear
1) PCIE A11 =3.3V , PCIE A13 AND A 14 = 0.5V ( ABOUT)
you can check cpu voltage appear at the main mosfet , up6282 _ ph1_ A for cpu voltage.
check Vccst_pwrgd .
If have then your PCI diagnostic card does not run means the bios CODE never run at all. It seems all your voltages do appear. So have to go to bios and use oscilloscope to check whether bios is read.
another thing u can check is superIO voltage detection Vin0 Vin 8.
or may be just...Leave a comment:
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Did u measure the ohms when u on your power ….?????
unplug power then measure , if so many shorted, liklely pch is shorted....Leave a comment:
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You got to check the main voltages whether all have …. Like ram voltage, 1.05v, vccio, 1.8 v etc. and the clock signal at pci slot …liklely your bios did not run at all.Leave a comment:
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First the output of the chip is 1.05v. There should be an inductor with it. If it is 1.05v, it is normal.
2nd if led stuck at vram,likely is ram issue or bios. Flash bios is surely easier then trouble shooting ram slot. Since this board had not been used, please clean the ram slot properly of the oxidation. It is likely ram slot issue.Leave a comment:
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It is normal. With processor, the low ohm is because it is directly connected to processor, hence very low like shorted. It is your gate measurements. You worry short / kill cpu, you have 2 choice. Get a spoilt cpu to try, Also you might wanna change both upper and lower mosfet together....Leave a comment:
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Burning mosfet again is a problem that will occur. How do you know is the VRM chip normal ? Is it possible to know is the VRM chip faulty ?
there are 2 issues here.
1) burning the cpu .
2) blowing the mosfet again.
answer to 1. If u do not put cpu , you cannot on the motherboard unless u are using MSI motherboard. Msi motherboard has a bypass pin to do it.
others need bypass SKTOCC signal at IO chip to cheat IO that there is a CPU.. then u can run without cpu.
answer to 2 . How to prevent mosfet burnt again if the problem is with VRM chip. I went...Leave a comment:
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3 ) the reset signal at PCIE A11 is high ? Yes, Its 3.3V, but sometimes it goes to 0V for a little time and again and again. If drop to 0V means, some voltage not stable… or cpu contact is poor. ..
the 0V is it due to psu or motherboard restart ?
is the clock signal at PCIE slot A13 A14 high ? I just have 300mV in those pins . Yes it is. Let me check AMD motherboard,which signal will cause a signal to bios chip.Leave a comment:
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another 2 things you can do: look under microscope for broken lines or missing parts....Leave a comment:
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