Need help to replace burned resistor in 350w atx psu

[mikey5791]

Hi to all forum members,

Got this faulty 350 watt atx psu dirt cheap from a local online seller as i am keen to use it as a learning tool to repair faulty power supply.
The faulty part is quite obvious from the burn area near the 16pin KA7500 BD pwm. The fuse is still intact with good continuity.

Upon power on ac, there is 5vdc standby power on cathode of diode D14 and about 10vdc on cathode of diode D13.(This should be the aux power to generate the 12v and 5v rail.)
Initially i replace the two burned resistors near my marked red arrow to 200 ohm resistor since i can't see the resistor color clearly. After power on ac, smoke came out from the second resistor., at the same time i detected 12vdc from the yellow rail and 5vdc from the red rail. Quickly i shut off ac power to prevent further damage.
On tracing the second burned 200 ohm resistor, it is connected to transistor at Q6(in front of the middle transformer), positive side of a 47uf 100v cap, then to a 4k resistor before going to pin 8 of pwm. The other end of the burned resistor is connected to pin 12 vcc of pwm.

If any of you has a schematic of this similar 350 atx psu, kindly share and point out the value of the burned resistor so i can continue to repair this psu and probably revive it. Thanking in advance.

[R_J]

Check this site and find a similar schematic, many of these power supplies are similar in that circuit it might be a 2.7k

[R_J]

The value might be 2.7k for both resistors, I would also replace the 10µf/50v or (1µf/50) (C40) and the 220µf/16 and the 47µf/50 (C04,C05)
I have seen some schematics that use 1.5k for those resistors as well

[lotas]

Resistor 1 kOhm

[lotas]

More like 1.5 kOm here. (Board version -10), and that version is -9.

[mikey5791]

The value might be 2.7k for both resistors, I would also replace the 10µf/50v or (1µf/50) (C40) and the 220µf/16 and the 47µf/50 (C04,C05)
I have seen some schematics that use 1.5k for those resistors as well

Thank you for all your replies. In my stock i seemed to have resistor value of 1k, 2.2k and 4.7k. Will it be ok if i changed both resistors(currently 200 ohm) to 4.7k to be on the safe side and expect the psu to run.
Kindly correct me if i am wrong.

[mikey5791]

Hi all forum members,

Yesterday i changed both the resistors to 4.7k ohm(color yellow, violet,red, gold) at the burned area and voila. The PG (power good) detected 5vdc, yellow rail got 12vdc, red rail 5vdc, orange rail 3.3vdc.
Fyi, i let it power on for 10 minutes, no smoke or any spark. Seems it is in working condition, but i will likely use it for some small electronic project .

Thank you to all who helped to revive this cheap psu. At least one less item goes to the salvage dump.