Electronics > Projects, Designs, and Technical Stuff

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

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CaptDon:
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?

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

floobydust:


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?

ejeffrey:

--- 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.

Gyro:
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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