Dell 330W AC/DC Adapter XM3C3

[wrand003]

Help!

I am trying to repair my Alienware M18r1 AC/DC power adapter. It is currently putting out 34V DC when it is supposed to put out 19.5V. This is preventing the battery from charging because it is triggering the safety protection. It is also causing it to throttle the processor performance. The adapter information is as follows:

Dell P/N: XM3C3
REF. NO.: ADP-330AB B
MODEL: DA330PM111

I believe the problem is with the below pictured regulators. The one with the markings "ZP" I have identified as a Central Semiconductor CMDZ16L but the one located at D136 is burnt so bad I cannot make out the markings. I am trying to locate a schematic for the adapter to confirm this. Any assistance is greatly appreciated.

[CapLeaker]

Kinda hard to believe that you are getting 34V out of a 19.5V, 16.9A switching PSU. I doubt the output caps are rated that high. Plus the OV protection circuit should kick in too.
Let’s say it doesn’t have any protection at all… still it would mean the gate drive circuit to the FET on the primary side is going full bore without any regulation from the feedback. Even then I don’t think you get 34V out of it.
Check your battery in your DMM and measure your PSU at the barrel connector again.

[wrand003]

Checked it again with new batteries still the same output from 34.85 to 34.88V DC pretty stable at these readings. If there is something else you would like to see just let me know and I will post it here. I am open to checking anything and everything at this point.

Picture attached.

[CapLeaker]

Man, that’s interesting!
Attach some straight shot high resolution pictures from top and bottom of the PSU, so we can see something.

[petehall347]

if you can find datasheet for ic139 it might have a suggested circuit .

[momaka]

Originally Posted by petehall347

if you can find datasheet for ic139 it might have a suggested circuit .

Concur. That would be a good start. Also remove diode D136 - its case looks cracked and blown. Remove the "ZP" diode too, if it shows shorted. Check if the resistor next to it has gone open-circuit.

[R_J]

IC139 is just a dual op-amp, D136 is likely a schottky diode of a few amps, I see another spot that has a zener and it is listed as ZD (ZD32), so D136 is not likely to be a zener.
IC140 looks like a TS391ILT
It may be helpful to post pictures of both sides of the complete board.

[wrand003]

It took forever to get the white adhesive off the pcb, but here is the photos. There is still more white adhesive on the reverse side but here is photos of what I have so far.

[wrand003]

Also, D136 is OL as well as the ZP diod. The resistor next to the ZP still reads good at 500 ohms.

[R_J]

I would guess D136 was a T4 1N4148W, but that is a very complex circuit so there may be more wrong than a couple diodes.

[CapLeaker]

Is the power cable from the brick to the laptop in good shape? Maybe worth unsoldering and checking the power again on the brick. To me that brick should shut down. Look at the brown output capacitor rating.