Dell PA-10 problems

[Gabriel]

I got this Dell PA-10 that wont work, when I plug in the ac cable the green light works for about 10 seconds and then slowly turns off without plugging it in to the laptop.

I thought the output caps was defect and changed them but same thing happend, even changed the startup cap - no change.

Measured the caps

kze 820uF 25V measures 824 0.04
taicon HD 470 uF 25V measures 433 0.09
ltec TH 10uF 50V measures 10 10

Soldered off the gnd and + cable too see if the cable had a short, no change.
Could not measure a short circuit in the cable.

I did leave the id signal connected when I did this.

Why would the powersupply behave like this ?

[Khron]

Re: Dell PA-10 problems

That Ltec TH 10u's ESR is a tad on the high side. No ESR mentioned in the datasheet (general-purpose 105c series), just a 45mA@120Hz ripple rating, but 10ohms is... just wrong

I also see two other small caps, right next to the main filter cap, have you checked (and/or replaced) those, as well? I don't see the white RTV-rubber disturbed yet

I've got a hunch that Ltec is "just" the Vcc filter cap for the PFC controller chip, and those other two "belong" to the main PWM chip (one of those being the ACTUAL "start-up cap" )

[selldoor]

Re: Dell PA-10 problems

Hi - could be a failing BIG cap? what voltage do you get across the legs? CARE high voltage. Can you do a better picture of the back of the board without flash. Good light is the key - try outside in daylight?

EDIT

Looking at te big cap again the covering is pulled away at the bottom did you do that?
If not I would wear eye protection when testing it.

[tom66]

Re: Dell PA-10 problems

This supply uses PFC too so it will have a separate cap for that.

[Gabriel]

Re: Dell PA-10 problems

Thanks for the tips guys. Was not aware of the PFC startup cap location.

I did remove the two Ltec small caps near the KMG and sure they both did not measure anything with the RusMike's tool.
Fitted Nichicon PJ and a Taicon is their place and now it is working.

Also removed the Ltech that measured 10ohm and fitted a PJ there too.

Thanks

[selldoor]

Re: Dell PA-10 problems

Good fix, well done, I have a few of these so now I'll know what to look for if they pack in.

[tom66]

Re: Dell PA-10 problems

Great to hear you fixed it, seems Ltec aren't even good as startup caps!!