Is There an Electrician in the House!?

By Inky960 ·
How's this for the newbie question of the month: I had to buy a replacement adapter for my laptop, and as I didn't want to pay $119 from HP, I bought one from a dealer of "generic" adapters. Only thing is, this one is 19v. My darling HP's adapter is only 18.5v.

Will this lead to any dire explosions or conflagrations? I'd hate like hades to murder my darling. (Faulkner said that, I just threw it in.)

Thanks guys 'n' gals,


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by robo_dev In reply to Is There an Electrician i ...

Some laptops are very picky about the exact voltage and will not work at all if the voltage is outside a certain range. Some Dell laptops even sense the current and give an error message if the machine detects the incorrect adapter.

OTOH, I'm not a bettin' man, but I would say there's an 95% chance that it will work just fine, without damaging anything, a 4.5% chance that it will work but cause laptop damage, and a .5% chance that a mushroom cloud the size of Lake Ponchartrain will be found over the remains of your home.

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Thank you.

by Inky960 In reply to Welllll

Jeez, all these great links and all this information - more than I needed to decide to send the adapter back. Heh. Maybe I should've bought an HP brand to start with, eh?


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My anthology of robo_dev metaphors is growing

by nepenthe0 In reply to Is There an Electrician i ...

I like this one better than the one about cleaning the basement floor with gasoline. robo_dev would command vastly higher fees writing scripts for Saturday Night Live...

Rick/Portland, OR

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Thanks, that made my day.

by robo_dev In reply to My anthology of [i]robo_d ...

I do earn a living writing, but it's only about all this boring IT security analysis stuff, application testing, rootkit exploits, penetration testing, etc, etc.

I could go on for hours about Oracle database security testing methods or the value of Enterprise Architecture in the global IT paradigm......yawwwwwn.

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TR is your creative outlet

by nepenthe0 In reply to My anthology of [i]robo_d ...

Here you can be yourself and let your imagination run riot without risk of incurring displeasure from the politically correct set. You have the talent, so I encourage you to use it. Your posts are priceless.

Rick/Portland, OR

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Will An Electronics Engineer Do?

by TheChas In reply to Is There an Electrician i ...

Well, there is a good chance that it will work, but:

A lot depends on the compliance and regulation of the new supply.

Just as important as the voltage rating is the current or wattage rating. If the current rating is not high enough, the adapter can overheat and will have a shorter service life. On the plus side with a laptop is that the batteries will fill in if the adapter does not have enough power to run the laptop in all modes.

Back to the voltage.

If I had this adapter in front of me, the first thing I would do, would be to measure the open circuit output voltage. If it is close to the rated 19 volts, that is good. If it is higher, that is a sign of a potential problem.

Next, I would monitor the voltage while connecting the adapter up to the laptop. If it drops down to the 18.5 volts, that could mean that something in the laptop is clamping the supply voltage. This can be bad for both the laptop and the adapter.

Next, I would keep an eye on both the laptop and the adapter for a couple of hours. If neither gets too hot, all should be good.

If the laptop gets hot near where the power plugs in, then the extra voltage is a problem. What I would do, is add a diode rated for at least 5 amps in series with the positive side of the adapter. It takes some work to do it right, so that it looks good and will be reliable. But a series diode will drop the voltage between .5 and .7 volts.

Any competent electronics tech can check this out and install the diode if needed.


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by Inky960 In reply to Will An Electronics Engin ...

This is great info, Chas. Thanks a bunch!


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CHAS has it covered

by mjd420nova In reply to Is There an Electrician i ...

The specs on the old versus the new needs to looked at carefully. Comparing the voltage is only half of the equation. The current rating is most important. The 19 volt will work fine if the current rating is the same. In most cases, users complain that the adapter gets very hot when in use. This is because the current being drawn is at or in some cases, beyond the normal rating and the adapter has to work hard to supply the needed current. When I replace an adapter, I will look for one that has a rating of at least 25% more that the original, this way it will run much cooler and last longer. The voltage rating is important but the amount of regulation it has plays a big part in how CLEAN that voltage is. Eighteen and a half volts with no ripple or impressed AC on top of it is good but a nineteen volt unit with a sizeable amont of ripple (half a volt or more) will not do the unit any good and may even cause unstable operation and could even cause a failure of the laptops internal regulator circuitry and thats not good.

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Wow Again!

by Inky960 In reply to CHAS has it covered

All this info is remarkably good. Thank you very much. I'm sending the adapter back; now I know what to look for


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by kayostar In reply to Is There an Electrician i ...

Have been experiencing this issue at the moment with my HP laptop. Not sure it's as straightforward as it may seem. Will have to seek a second opinion concerning it.

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