MT6265 notebook power brick repair

[pdavid]

A decent looking universal power adapter that's available here as replacement. It bleeds from multiple wounds. Bad primary cap, dead pwm and fet, weak soldering at someplaces, I hope I can get this fixed.

[pdavid]

Re: MT6265 notebook power brick repair

Let's see what else is bad... some fried resistors, fuse is good, secondary caps... hmm.

Original pwm was an A0b2269CP. My collegue who repairs tvs and such says I can use the sg6841 as replacement. I got some of those. I got a new Epcos 150uf/400v primary cap. I also need smd resistors, 10ohm, 22ohm, 3.3ohm... I fixed up the loose solder joints. Secondary has two mbr20150ct schottky, those are good, as well as the other diodes. The two 47uf 50V startup caps have their capacity so I guess those will stay.

Most importantly would an irf840 be suitable in place of the mdf11n60?

[pdavid]

Re: MT6265 notebook power brick repair

I got everything in place, plug it in and all I got is 313 volts from the bridge rectifier and nothing else. No smoke no fire. Damn, I don't know how to configure an sg6841 for this thing

[momaka]

Re: MT6265 notebook power brick repair

The two 47uf 50V startup caps have their capacity so I guess those will stay.

While this may not be the problem you're currently having, don't be fooled by thinking they are okay just because they have right capacitance. Their ESR also matters. One member on here had a PSU for a speaker amp that had its start-up cap fail. He measured the capacitance and it was good, but the ESR was high.

Damn, I don't know how to configure an sg6841 for this thing

Post a clear picture of the underside of the primary (the one you provided in post #1 has flash and is hard for me to read).

Looks like the sg6841 PWM should be compatible with this circuit. Therefore, check SMD resistor R19, the diode between the two start-up caps. If they are good, check the voltage at pin 7 of the sg6841 PWM IC. Make sure to measure the voltage with respect to hot ground (the [-] on the big capacitor on the primary).

[pdavid]

Re: MT6265 notebook power brick repair

Lets see. I get between 12 and 15 volts dc from pin7. Diodes and resistors are good. I replaced the bad ones with the same value.

Since I'm at work now I can measure esr. Startup caps have above 1ohm, caps at secondary 0.06-0.05. I put everything back and noticed a small solder blob on the seondary but it wasn't shorting anything. Still no change.

[pdavid]

Re: MT6265 notebook power brick repair

Smd resistors on primary side:

RX1/2 5103

R1/R2 2004
R3/R4 3303
R5 3902
R6 3902
R7 10R0; was replaced with same value
R8 22R0; was replace with same value
R12 2001
R13 1502
R15 2402
R16 5100
R19 3R30; was replaced with same value
R27 1002