I have a dell laptop that won't power on or charge the battery but ran fine on battery until the battery lost its charge . I checked the DC output of the AC adapter with a multimeter and it constantly fluctuates from 18.5v - 19.5v.
I have another laptop a toshiba which happens to have an adapter with the same output 130w 19.5v 6.7a and when I measured it the output stayed at exactly 19.3v.
The toshiba adapter has a 2 prong input from the AC plugin and the Dell adapter has a 3 pronged plugin on the AC side. Is the fluctuation on this type of Dell ac adapter normal? Or is the fluctuating DC output the reason that the laptop won't start or charge the battery?
Did you measure that fluctuating Dell adapter output with an appropriate load applied? I have seen this sort of behavior from an unloaded adapter, which technicians decided was OK since it was the right voltage range. But as soon as a decent load was applied, the output dropped to zero.
Best regards,
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
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I did not test the output under load. I would like to so I can see what happens but I am not sure what I should use as a load. Using the laptop is very hard since the motherboard has to come out in order to have access to the pins for testing. The adapter output is rated for
19.5 volts 6.7 amps. Do you have any suggestion for what I could use as a load so I can test the adapter
You don't need to draw the full 6.7 amps, just something reasonable. Even pulling an amp or less will probably be enough to show if the adapter is shot... at least it was in my case.
The biggest problem is often making connection to the output of the power adapter. In my case, I just stuffed the leads of the resistor into the holes of the adapter, with the meter clipped onto the leads.
If you have a power resistor (bigger than 19.5/6.7 = 2.9 ohms but less than say 20 ohms) you can try that, or wire a bunch of lesser-wattage resistors together. You won't need to test for more than a second or so, just enough to get the reading: Low-wattage resistors may get hot really fast, but you can get a reading just before you burn your fingers. (And getting hot is a Good Thing, since it tells you the adapter is at least putting out juice... mine wasn't.)
Note that when you combining low-wattage resistors to get a higher power rating, it dosen't matter (to the effective power rating) whether they are in series or parallel. So 10 x 1 ohm
1/4 watt resistors in series gives 10 ohms at 10*(1/4) = 2.5 watts. Or 10 x 100 ohms in parallel gives the same thing.
Best regards,
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
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Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!
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