fault in laptop charger 65 W lenovo usb c (adlx65ycc3d)

[claws77]

the laptop charger does not work. not output voltage.
removed 18V and GND cable from secondary, left ID cable-- suspecting short in output cord and then measurements were made.
input cord is fine -- checked. 220 V AC
primary transformer voltage (V_DE) is fine - checked 310.1 VDC
secondary transformer voltage is 0V (V_AB) -dont know why
C1 and C2 are electrolytic caps marked at 470uF but reads 987 uF -- seems connected in parallel. V_c1 =0V and V_c2 = 0V.

[mon2]

Hello.

1) this may be a post that is better suited for posting in the power supply forum:

Troubleshooting Power Supplies and Power Supply Design - Badcaps

2) yes, if the caps are in parallel then the total capacity will be the sum of the 2 capacitors.

3) Being a Type C power adapter, the power adapter should start with a default power value of 5 volts. Only after a proper communication over the CCx (single wire BMC signalling), the target / consumer side of the connector will request the list of power delivery (PD) contracts (voltage & current pairs). After receiving this list, the consumer will decide on the best PD contract that is useful to power its load. Often this is a 20V PD contract. You can source various PD bus analyzers to monitor this traffic using a host PC. Features will vary with the tool's cost.

With no power to the adapter. You can review the DIODE mode measurements of each contact on the USB Type C connector. Red meter probe to GROUND. Black meter probe to the point to test. If you measure ~0 volts, then that pin is shorted.

[rogfanther]

From the picture, seems to me the charger is of a normal type, with resistor divider at the tip . Or are these usb-c chargers ( I have not worked with one of these yet ) like Apple chargers, with a pcb on the tip ?

claws77, after cleaning more of that white glue, can you measure voltage at the main capacitor, and also identify the markings on the charger controller IC ?

[claws77]

after cleaning more of that white glue, can you measure voltage at the main capacitor, and also identify the markings on the charger controller IC ?

i do not know what you mean by main capacitor
i can see 3 electrolytic capacitors(one big on input and 2 on output)
input capacitor has 320 V
output ones have 0V each.

it is WT6633P. (a W is missing from image)
and the primary controller chip, is LD5763GS i think

[CapLeaker]

Probably the weltrend chip disabling the output. Check the fault pin for active low.

[claws77]

LD57636S IC has a short.
this black something(first from left) has a short too.
removing the IC and the black thing the short goes away.

[CapLeaker]

https://www.leadtrend.com.tw/images/...0122155721.pdf datasheet

Check the mosfet and the gate drive too...

[claws77]

which pin of LD576 pins are you talking about?
or are you talking about on the PCB.

there are mosfets on both primary (one) or secondary sides(two)

primary side mosfet is short (in circuit measurement)

but no short on secondary side

[CapLeaker]

You found the PWM shorted on the primary. Right now you don't know why it did that. Chances are very high, the MOSFET on the primary blew and thus took the PWM with it. If you don't check the gate drive circuit between the PWM and including the MOSFET, you may blow the PWM again since the MOSFET gate is shorted to its drain and source pins.
Ive seen a PWM just play dead, but that is very rare,

[claws77]

[CapLeaker]

You have to figure out why VCC is shorted to GND. Is it the PWM or something else before that. This is your first problem to solve. After you figured this out you need to look at the gate drive and check if the MOSFET is shorted. That diode you circled should show on your DMM in diode mode open one way and a voltage drop of 0.5 the other way. If not replace it and check these resistors too.
off course this is just an example circuit and things are probably different on your PSU.

[stj]

did you clean all the rubber crap off the top?
these really compact designs are shit, when something fails it often arc's across to other parts!
you may get lucky, i had one where a 4wire choke on the topside had a burned leg on it from poor soldering - i just replaced it with a pair of jumpers.

[claws77]

stj, yes i cleaned all the white goo , checked primary mosfet (shorted), primary PWM ic short, gate drive diode is open.

did not find any such obvious shorts in secondary side.

since i do not have the necessary parts
i am thinking of using this board to understand and repair other SMPS
or if i get lucky with parts maybe repair this one

thankyou everyone