Dell Inspiron Laptop PSU/Filter Problem
Dr. Who, Thu Apr 27 2006, 05:11PMI've currently got a dead Dell Inspiron 510m laptop in bits on the bench. Input is 18V DC from an external PSU. The input goes through what looks like a common-mode choke, the positive side of which presents an impedance of meghoms and hence appears to be faulty. The negative side is OK.
Not being an expert on SMPS, I'm wondering whether its safe to try shorting the positive side of the choke. Most SMPS have some sort of inrush suppression (e.g. NTC resistor), there doesn't seem to be any such protection obvious here, although it is fed by another SMPS with an amp or 2 of maxiumum output, rather than the mains.
My other thought is whether this is the primary fault, or whether it's failed as a result of a fault in the laptop's PSU that has drawn an excess current?
All comments and good ideas gratefully received.
Re: Dell Inspiron Laptop PSU/Filter Problem
Desmogod, Fri Apr 28 2006, 12:55AM
Be careful messing with Dell PSU's, not sure if you are aware, but there is actually 3 electrical faces on the plug.
The outside of the "cylinder" of the plug is -, the inside of it is +, and the pin in the centre is + for charging the battery.
Desmogod, Fri Apr 28 2006, 12:55AM
Be careful messing with Dell PSU's, not sure if you are aware, but there is actually 3 electrical faces on the plug.
The outside of the "cylinder" of the plug is -, the inside of it is +, and the pin in the centre is + for charging the battery.
Re: Dell Inspiron Laptop PSU/Filter Problem
Steve Conner, Fri Apr 28 2006, 11:22AM
That choke is probably just to make it meet EMC regulations. I reckon it should work fine shorted. As for whether it was burnt out by excess current draw, you'll find out soon enough >_<
Steve Conner, Fri Apr 28 2006, 11:22AM
That choke is probably just to make it meet EMC regulations. I reckon it should work fine shorted. As for whether it was burnt out by excess current draw, you'll find out soon enough >_<
Re: Dell Inspiron Laptop PSU/Filter Problem
Dr. Who, Fri Apr 28 2006, 07:52PM
Thanks guys. It works fine with the choke shorted.
This PSU's slightly different, it has the plug you describe, but the centre pin is a data line to detect a genuine Dell PSU, part of another sinister ploy to force you to buy their overpriced spares.
Dr. Who, Fri Apr 28 2006, 07:52PM
Thanks guys. It works fine with the choke shorted.
Be careful messing with Dell PSU's, not sure if you are aware, but there is actually 3 electrical faces on the plug.
The outside of the "cylinder" of the plug is -, the inside of it is +, and the pin in the centre is + for charging the battery.
This PSU's slightly different, it has the plug you describe, but the centre pin is a data line to detect a genuine Dell PSU, part of another sinister ploy to force you to buy their overpriced spares.
Re: Dell Inspiron Laptop PSU/Filter Problem
Avalanche, Fri Apr 28 2006, 08:45PM
That's insane
Although I suppose it would be of some use if it protects your laptop from being plugged into the wrong PSU
I recently had to repair a laptop which someone had gone and plugged into a random wall wart, dismantling a whole laptop and solding a tiny SMT fuse was not fun
Avalanche, Fri Apr 28 2006, 08:45PM
That's insane
Although I suppose it would be of some use if it protects your laptop from being plugged into the wrong PSU
I recently had to repair a laptop which someone had gone and plugged into a random wall wart, dismantling a whole laptop and solding a tiny SMT fuse was not fun
Re: Dell Inspiron Laptop PSU/Filter Problem
Conundrum, Sun Apr 30 2006, 03:16PM
Watch out, those chokes are part of the suppression system. Taking this out means high frequency noise from the PS can get into the laptop, potentially causing instability.
I'd replace the choke unit if possible, or solder in a homemade replacement with sufficiently thick wire on a former.
Then again, if it works.. :)
-A
Conundrum, Sun Apr 30 2006, 03:16PM
Watch out, those chokes are part of the suppression system. Taking this out means high frequency noise from the PS can get into the laptop, potentially causing instability.
I'd replace the choke unit if possible, or solder in a homemade replacement with sufficiently thick wire on a former.
Then again, if it works.. :)
-A
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