Lenovo 135W charger

[Askic]

Hello electronics experts,
My lenovo 135W charger ADL135SCC3A failed days after the warranty is expired. With some effort I open the adapter without breaking the plastic and found that first input fuse T4A 250V is blown. This is the first components at the charger grid input and there is a good chance that it protected the rest of the circuit from the external overvoltage. Input is 100-240Vac, 2.5A, output is 20V, 6.75Adc.
Replacing the fuse is trivial, but I wonder if there are some other components I need to check just in case that the fuse is blown due to some malfunction inside the adapter.
Most of the components are covered with some kind of rubber/silicone material and it is very hard to approach them.
Did you have any similar experience?

Any advice is welcomed.

Thank you!

P.S. Notebook is Ok and the battery is charging normally with another adapter. This charger was needed because of the Dock station.
Maybe I made mistake, most of the time adapter was plugged to the power grid even when not used.
Maybe I should have kept it unplugged when not used.

[SMDFlea]

Re: Lenovo 135W charger

Are there any swollen capacitors, post some pictures .

[stj]

Re: Lenovo 135W charger

is this a really compact psu?

i have a very small lenovo psu here that tripped a 32A breaker because the input choke was arcing.
these assholes are making stuff too small with no space between the parts!!

[Per Hansson]

Re: Lenovo 135W charger

Check the primary side 450v capacitor, it could be bad:

https://www.badcaps.net/forum/showthread.php?t=63573

[Askic]

Re: Lenovo 135W charger

Hello guys and thank you for the replies. It's really hard to make any useful picture. Practically the only component I had access to was bad.

The lower part has metal casing that is soldered into PCB board. I need to remove this first to check for the big capacitor.
I don't know what is the English word for this white material that is used to cover the components. It is very hard to remove.

[japlytic]

Re: Lenovo 135W charger

In one AC adaptor I have handled, the X-class EMI filter capacitor has failed short circuit since the density of the capacitor was a bit too high for a particular manufacturing technique.

[Askic]

Re: Lenovo 135W charger

It's not that easy to dig out components to measure, this would be more significant effort. The fuse is replaced but blown again immediately when power is connected. The replacement part is ordered. This one will end up in the garbage. They made it in such way to prevent any repair.

Thank you all for your replies.

[eccerr0r]

Re: Lenovo 135W charger

Yeah this is generally called "potting material" and whether it's a thermoplastic or thermoset plastic/silicone rubber is the question, usually the latter for thermal stability.

If it's soft, you can slowly pick at it; if it's hard, yeah, that's virtually EOL.

Appears that Per Hansson got lucky with less potting, in your case you won the prize...
So much for throwaway electronics. *sigh*

[Dumah Brazorf]

Re: Lenovo 135W charger

Usually when the fuse is blown probably the main mosfet has failed and also the main bridge rectifier is gone. The main cap can also be gone for age and heat.

[momaka]

Re: Lenovo 135W charger

Wow, so Per's adapter blew its primary cap, and it's a Japanese UCC rated for 450V, nonetheless.

This is why I still hate APFC designs! Moreover, the newer they are, the more complex and troublesome they seem. They can shove those efficiency numbers up their rear if the end result is a mountain of e-waste in the landfill because the adapters don't last worth a damn.

In the case of the failed primary cap, I suspect the AC cycle skipping (rather than PWM pulse-skipping) probably lets the primary cap voltage go between 170/330V DC and 390V DC quite often. If the designers of the IC even bothered to read any electrolytic cap datasheet, they should know that regular electrolytic capacitors are actually NOT meant to be used like batteries, where they could be subjected to frequent large jumps in operating voltage. This WILL destroy most regular electrolytic caps (and is also one of the reasons why power-cycling electronics too frequently is not a good idea.)

I can't remember what datasheet I read this from, but it was from one of the Japanese manufacturers for their larger HV electrolytic caps. It said to limit full charge-discharge cycles (i.e. going between max DC voltage and completely discharged) to something like no more than 10 times per day (I don't precisely remember what the guide was... I'll see if I can find that datasheet again.) Any more, and degrading of the cap can occur.

So on that note, PWM pulse-skipping for the APFC is probably a lot safer in the long run.

[ChaosLegionnaire]

Re: Lenovo 135W charger

or the other alternative is to just bypass the apfc section with 16awg jumper wires. fock apfc if it doesnt work and kills more shit. this is just more fascism by the energy companies imposing their will on the consumers. this is not the vip room so i wont comment further on this...

[momaka]

Re: Lenovo 135W charger

or the other alternative is to just bypass the apfc section with 16awg jumper wires. fock apfc if it doesnt work and kills more shit.

I already tried that on an Enermax PSU:
https://www.badcaps.net/forum/showpo...4&postcount=11
https://www.badcaps.net/forum/showpo...8&postcount=14
and while it works, it doesn't work too well.

I suppose I never updated that thread, but the Enermax PSU shuts down when trying to pull more than around 250-270 Watts, if I remember correctly (couldn't power my OC-ed Q6600 and GTX 560 with an OCCT GPU+CPU stress test.) So disabling the APFC circuit does lower the power output capability of the PSU significantly, unfortunately.

[stj]

Re: Lenovo 135W charger

it may have worked better if you had 230v going in to it.

[momaka]

Re: Lenovo 135W charger

it may have worked better if you had 230v going in to it.

I did. I have a 120<-->240V transformer.
Didn't make a difference between that and after when I installed 2x 200V caps on the primary and set them up as a voltage doubler.

[budm]

Re: Lenovo 135W charger

APFC boost the the Voltage (roughly regulated 380~ 400VDC) to run the circuit so at 230VAC without booster you will have about 325VDC (depends on AC line Voltage), the power supply will draw more current to maintain the output, the MOSFET will also get hotter to due to more current flow.
But then the bad part is that APFC blows up a lot.