Unknown component in 19V power supply

[rddube]

Hi everyone,

Anyone have any idea what this component is in an Acer Swift 3 laptop power supply?

Many thanks!

[R_J]

Re: Unknown component in 19V power supply

Why multiple posts for the same problem?
Your answer is below

[lotas]

Re: Unknown component in 19V power supply

Ld5533h

[rddube]

Re: Unknown component in 19V power supply

Why multiple posts for the same problem?
Your answer is below

Sorry, I thought I hadn't posted it in the right section. Should I delete one of them?

[rddube]

Re: Unknown component in 19V power supply

Ld5533h

Thank you Lotas!

[R_J]

Re: Unknown component in 19V power supply

Sorry, I thought I hadn't posted it in the right section. Should I delete one of them?

No it's ok, you can't delete threads
Why do you suspect this ic is bad? What voltages etc. have you checked so far? Check that you have voltage ACROSS the main filter cap (165vdc)

See the pdf, the output should drive a mosfet's gate, There will be a resistor from the mosfet source to ground, check that it is not open, it should be around 1Ω or less If it IS open the mosfet is likely shorted, if it is ok then I suspect the problem is elsewhere.

[rddube]

Re: Unknown component in 19V power supply

No it's ok, you can't delete threads
Why do you suspect this ic is bad? What voltages etc. have you checked so far? Check that you have voltage ACROSS the main filter cap (165vdc)

See the pdf, the output should drive a mosfet's gate, There will be a resistor from the mosfet source to ground, check that it is not open, it should be around 1Ω or less If it IS open the mosfet is likely shorted, if it is ok then I suspect the problem is elsewhere.

Hello R_J!

Across the filter cap I am getting 166V.

I am getting 12V on the VCC pin (pin 5) and 0 on the output (pin 6). Where is the source pin? Do you mean CS pin 4?

Many thanks for your great advice!

[R_J]

Re: Unknown component in 19V power supply

You would need to provide pictures of both sides of the circuit board to start troubleshooting.
12v on the vcc pin is good You would need a scope to see what is on the out pin for drive. The out pin should connect to a mosfet gate. This ic can not drive the transformer directly.
The source pin is on the mosfet, the CS pin will connect to it via a resistor.

[rddube]

Re: Unknown component in 19V power supply

You would need to provide pictures of both sides of the circuit board to start troubleshooting.
12v on the vcc pin is good You would need a scope to see what is on the out pin for drive. The out pin should connect to a mosfet gate. This ic can not drive the transformer directly.
The source pin is on the mosfet, the CS pin will connect to it via a resistor.

Hello RJ,

Tried to take pictures, on one side the one in the picture there was a lots of white hard glue that I had to remove. I discovered under the glue a damaged RS1M diode and since I didn't have a RS1M I replaced it with an FR107 diode. You're right, the out pin connects to a mosfet gate, as you will see in the photo (i removed the mosfet and C6, which I will replace), but I have 0V at the output of the mosfet. Here is a photo with some explanations. Tks!

[rddube]

Re: Unknown component in 19V power supply

Also, not much purpose on taking a photo of the other side, it is filled with glue and you see absolutely nothing. I would have to remove all that glue and it is a mess. Here is a photo anyways.

Tks.

[R_J]

Re: Unknown component in 19V power supply

There seems to be a bad solder connection on a component, can you check what it is and where it connects?

What do you mean RS1M diode was damaged, physically broken, shorted, open? Looks like it could be D2 on the datasheet schematic

[rddube]

Re: Unknown component in 19V power supply

There seems to be a bad solder connection on a component, can you check what it is and where it connects?

What do you mean RS1M diode was damaged, physically broken, shorted, open? Looks like it could be D2 on the datasheet schematic

That is one of the legs of the little transformer, and it is not connected, no solder point there.

When I removed the glue, the RS1M diode lid just came off. Is the photo clear enough?

[R_J]

Re: Unknown component in 19V power supply

The transformer primary is connected between the + of the bridge rectifier and the mosfet drain, there should also be a feedback winding that supplies run vcc voltage for the ic. One end of the feedback winding connects to hot ground the other feeds a diode and then pin5 of the ic

[rddube]

Re: Unknown component in 19V power supply

Ok, so what do you think I should be checking next?

Tks.

[R_J]

Re: Unknown component in 19V power supply

Did you check the feedback circuit? You did check to make sure there was no shorted output on the secondary side, like shorted cable, shorted output diode etc.

[rddube]

Re: Unknown component in 19V power supply

Still learning R_J, what does the feedback circuit look like? I'll check for shorts on the secondary side of the transformer and report back.

[R_J]

Re: Unknown component in 19V power supply

The feedback is a winding off the transformer, (T1B) which connects to R4, and D1 diode to supply the run vcc for the ic. Your component designations will be different but the circuit should be the same.

[rddube]

Re: Unknown component in 19V power supply

Ok, so I checked every component on the back of the board and didn't find anything suspicous, except for a T4 diode that was in parallel with a 100 ohm resistor, so I removed it and it tested good.

Took out the little transformer and the output seems shorted as can be seen in the photos with my blue ring tester compared to a good coil. Also took a closup of the inside for your info.

I guess this means I will have to retire this power supply and keep it for parts with the exception of the transformer, right?

[lotas]

Re: Unknown component in 19V power supply

You are not diagnosing correctly, you need to check not the output winding, but the power winding, where the output is from the mosfet.

[R_J]

Re: Unknown component in 19V power supply

I doubt the transformer is bad, Check the resistance of the windings, if they are not open I suspect the transformer is ok. Did you check the primary and feedback windings with your ringer?