Electronics > Projects, Designs, and Technical Stuff

P.O.S. Chinese SMPS killed my laptop!!

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Should have been more careful, should have known!! 19VDC SMPS with '2-prong' line cord and no ground. Had my laptop powered up and when I plugged the audio cable from my grounded (a.c. cord with three prongs) guitar amplifier into the laptop KA-BOOM....smoke rolls out of the laptop!
Looks like the .33uf cap from the A.C. line inside the SMPS failed dead short!! I must have been shit lucky in the past to have plugged the non-polarized 2 prong line cord into the outlet in such a way as the .33 cap was on the neutral side and didn't cause a problem? I have used this setup before with no smoke but today cost me a laptop!! Motherboard was blown big time. Old dinosaur guitar amp still works perfect! The 1/4" input jack is chassis grounded steel to steel and the chassis is grounded via line cord. Laptop became the fuse!!! I did get some satisfaction beating the shit out of the power supply with a hammer!! Kind of strange the 2 prong power cord wasn't polarized? May not have mattered?

Likely a non-safety rated Y capacitor that failed short.


After seeing Big Clive's adapter fail teardown, where it shorted mains HV DC bus to output(-) due to the hazardous live heatsink shorting to the output inductor, very scary, fuse was bypassed. No hi-pot test, fake safety approvals.
OP a 0.33uF film cap is X-cap and should not kill the laptop. Wonder what this cap is that failed short. Y-cap is typ. 2,200pF ceramic.

Why do people pay and power expensive stuff worth $1,000's dollars from cheap chinese unsafe power supplies?


--- Quote from: CaptDon on February 25, 2024, 10:08:27 pm --- Kind of strange the 2 prong power cord wasn't polarized? May not have mattered?

--- End quote ---

Not much reason for an ungrounded, "double insulated" power brick to be polarized. There is not even any obvious way to choose which side should be neutral.

Without seeing photos of the OP's SMPS (which would be very interesting). I suspect that the primary - secondary capacitor is actually after the bridge rectifier and so, plug insertion direction independent. With an improperly rated or fake Y cap (I don't understand the 0.33uF, more likely would be a 3300pF), catastrophic failure is only a matter of time, and maybe a mains spike away!


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