Dead power adapter

[kamel]

Hi members,
Came to me a dead power adapter for repair. Model PA-1400-14 with output 19V-2.1A

Replaced s/c power fet k3562 with a recovered working one, replaced an open 0R6 source sense resistor, and 2 open smd gate drive resistors. Used a bulb in ac input and plugged adapter. No more s/c, so replaced the shorted fuse and plugged adapter. Led indicator came and 19v also, but led went off under load.

Every component Checked with ohm-meter ok. Replaced every electrolytic cap. No result.

Measured PWM IC "marking end is 754M" which seems having same pinout as FAN6754MR : start voltage is oscillating from 20V to 80v. All other pin voltages are also oscillating (Ic vcc, fb as well as gate switching fet drive).

Any clue.

Thank you

[Dgtech]

Re: Dead power adapter

so replaced the shorted fuse

[Dgtech]

Re: Dead power adapter

I can understand the curiosity of fixing this power supply, but they are easily available on ebay for replacing. Like $10. You put more than $10 worth of time and energy into this one. Even if fixed, it may not last as long as simply replacing it.

[stj]

Re: Dead power adapter

"compatable" psu's are junk,
an original costs $50+
that's why they are worth fixing.

yea, cought that bit about the fuse last night!

[kamel]

Re: Dead power adapter

I can understand the curiosity of fixing this power supply, but they are easily available on ebay for replacing. Like $10. You put more than $10 worth of time and energy into this one. Even if fixed, it may not last as long as simply replacing it.

Dear colleague, Money is not everything.

Money goes, knowledge remains.

[bammbammfran]

Re: Dead power adapter

pictures would be nice

[jetadm123]

Re: Dead power adapter

Assuming the K3562 is the switching transistor for the PWM, when it shorted out, it probably damaged the FAN6574.

[kamel]

Re: Dead power adapter

Assuming the K3562 is the switching transistor for the PWM, when it shorted out, it probably damaged the FAN6574.

Your conclusion is logic. I'm going to replace FAN6754MR tomorrow and see.
If not fixed will replace the optocoupler as a last resort. Main suspected components being already changed.

[kamel]

Re: Dead power adapter

pictures would be nice

If not solved after changing FAN6754MR and optocoupler, I'll post a picture.

[kamel]

Re: Dead power adapter

FAN6754MR is not available over here. Returned the adapter to the customer and unfortunately did not figure out the problem.

Thanks for every contributor.