Toshiba adapter fails to power up laptop

[kamel]

Toshiba 30W Adapter Model : PA3743U-1ACA is failing to power up laptop.
Laptop tested ok with an other adapter.
19V is ok at output pins but without load.

Steps taken :
Electrolytic caps changed with no avail.
Power transistor and output reg Ic measured ok on circuit.
Zener diodes tested ok.
Board inspected, no burned item.
A dry joint cap in output section resoldered

Any clue

[stj]

Re: Toshiba adapter fails to power up laptop

connect a load like a 24v light bulb to the pcb - does it stay lit?
if yes, connect it to the end of the cable & try again.
broken wires in the cable are common on chargers.

[kamel]

Re: Toshiba adapter fails to power up laptop

connect a load like a 24v light bulb to the pcb - does it stay lit?
if yes, connect it to the end of the cable & try again.
broken wires in the cable are common on chargers.

Cable is desoldered.
Forget to mention that when I connect a 24v load bulb to output pins of adapter, bulb cycled on/off .

any new clue

[stj]

Re: Toshiba adapter fails to power up laptop

did you test the actual breakdown voltage of the zeners or just the "one-way" test on a multimeter?
only other thing that comes to mind is a possible optoisolator problem.

well not the only other thing,
i'v seen diodes & transistors that "work" on a meter, but when you put a load on them they stop working.

[Th3_uN1Qu3]

Re: Toshiba adapter fails to power up laptop

Resolder or replace TL431 on the secondary. I've had the exact same problem with a 9v 2A tablet power adapter. After replacing caps with no success, i started touching up the soldering. After i resoldered the TL431 the power supply came back to normal.

[kamel]

Re: Toshiba adapter fails to power up laptop

did you test the actual breakdown voltage of the zeners or just the "one-way" test on a multimeter?
only other thing that comes to mind is a possible optoisolator problem

.

No, I just made the "one-way" test on circuit. There are 2 zener diodes, one is 22V and the second, marking is not readable. Optoisolator measured on circuit seemed to be ok.

well not the only other thing,
i'v seen diodes & transistors that "work" on a meter, but when you put a load on them they stop working.

Noticed that voltage on the main Cap is stable but on drain of P4NK60Z is fluctuating all the time when load is applied to the output pins of adapter.

Also there is a 6 pins Ic linked to optoisolator marked "IbP", which i can not verify the good functioning (no datasheet is available).

Any idea on the pinning of this IC ?
Is there any good link to diagrams of branded lap power supply adapters for download (Toshiba, Hp, dell...)?

[kamel]

Re: Toshiba adapter fails to power up laptop

Resolder or replace TL431 on the secondary. I've had the exact same problem with a 9v 2A tablet power adapter. After replacing caps with no success, i started touching up the soldering. After i resoldered the TL431 the power supply came back to normal.

No TL431 in the failing Toshiba adapter, but rather a 6 pins Ic marked IbP, which I can't identify !

[stj]

Re: Toshiba adapter fails to power up laptop

how many of the pins actually connect to anything?

[kamel]

Re: Toshiba adapter fails to power up laptop

how many of the pins actually connect to anything?

Are you speaking about the 6 pins IC marqued "IBP 32" ?

[stj]

Re: Toshiba adapter fails to power up laptop

yes.

[kamel]

Re: Toshiba adapter fails to power up laptop

yes.

Main pins of IC "IBP 32" :
5 -linked to AC voltage through 160k and 120k resistors (likely startup resistors).
1 and 2 are linked separately to output pins of opto-isolator (for feed back)
6 is linked to Gate of power transistor through // diode and Resistor 51ohm connected to 10ohm resistor.

I Hope this will help understanding the IC and finding the culprit.
Any new suggestion or question is welcome.

[budm]

Re: Toshiba adapter fails to power up laptop

That sounds more like SMPS IC to me. Any good pictures of top and bottom side of this power supply board?

[stj]

Re: Toshiba adapter fails to power up laptop

well that's obviously the controller,
never mind - i thought it may just be a current-source.

i'd try changing the 4nk60 output fet.

[budm]

Re: Toshiba adapter fails to power up laptop

Probably something similar to these:


https://cdn.badcaps-static.com/pdfs/...3ad9163b64.pdf
The symptom sounds like bad start up cap in the primary side.

[kamel]

Re: Toshiba adapter fails to power up laptop

Further to my posts and wish to give a feed back.

IC "IBP 32" was identified as SMPS controller.
Diodes, resistors, caps and other components checked ok.

As no problem found, I desoldered output cap and though it checked ok with atlas esr meter, I soldered a new one and surprisingly problem was fixed.

If this help any member please message.

Many thanks for every poster.