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Spyril

Is this AC adapter defective?

9 posts in this topic

Recently the AC adapter that came with my laptop ceased to work due to a broken wire. Since I'd be damned dishing out $90 to the cheap bastards at HP for a replacement, I decided to get a slightly different one off of ebay for $14. I made sure to get one with a slightly lower output voltage rating, so I figured that the worst thing that could happen would be the laptop not receiving sufficient power. It works fine, but the first time I plugged it in, a noticed a strange low-pitch buzzing sound coming from the DC jack. It hasn't happened since, but I thought that was a little odd. The other thing is, when I plug the connector into the DC jack, the LED light on the power brick temporary goes out, then comes back on again in 15 seconds or so.

Should I be using this adapter or should I send it back and buy something else?

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There's no point in risking your laptop with the incorrect adapter. Get one with the right specs.

While I don't see anything major going wrong with your laptop, there is a possibility of something going wrong with the adapter. Trying to draw too much current from a small adapter can make it fail. This can be anything from it not working anymore, to a pop and fizz, to sparks, to a fire.

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Ohm is right, you should get one with the same voltage and at least the same current (or power) rating. Otherwise you may be risking damage to you laptop. Check on Ebay and the like, you should be able to get one cheaper than that. You might also find non-OEM equivilant.

You mention a broken wire on the old supply, can this be repaired?

Mungewell.

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Well, I've done some reading on the adapter I bought, and it says that it has overcurrent protection, and it's safe from overvoltage and shortcircuting. My original AC adapter was a 90W with an output of 19v, and my new one is 65W with an output of 18.5v. On both adapters descriptions, they say that it's compatible with my laptop, an HP dv7. I'll also mention that for a week or so, I used my mom's HP AC adapter, which has basically the same specs as this one.

With that info, do you still see a danger? I'd really prefer not to have to send it back...

Ohm is right, you should get one with the same voltage and at least the same current (or power) rating. Otherwise you may be risking damage to you laptop.

Ah, I thought that it was safer to go with a lower power rating than a higher one.

You mention a broken wire on the old supply, can this be repaired?

I brought the old supply to someone who knows much more about soldering / wiring than I do, and he had a hell of a time trying to fix it. The break in the wire was very close to the power brick, which made it difficult to work with the wire. There was no easy way of opening the brick either. Also, apparently the cable was a triaxial cable rather than the usual coaxial one, which made it hard to keep the shit separate. That's what I got out of what he told me, anyway.

Edited by Spyril
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Half a volt difference probably won't matter. The computer itself will be run on regulators, as well the battery recharge circuit. So the voltage will be regulated down to 12v or so and evened out.

The wattage is something to worry about. Using your computer and charging the battery at the same time (especially if your laptop has some kind of quick charger) can easily use more than 65 watts. If you use this one, maybe don't use it to recharge the battery and power the computer at the same time?

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While it is safer to use a lower voltage than higher one, its not smart. It requires 19 for a reason, but there should be some internal play that will let that slide (Laptop power bricks are regulated, so there won't be too much play room)

Second, there is a reason that HP pays for and makes you pay for, a 90w brick. Even in bulk, a 90w brick will cost more than a 65w brick, and if HP thought the laptop did not need 90 watts, then it would not bother.

A 90w brick gives (90/19)=4.7 Amps at max. A 65w brick give's (65/19)=3.4Amps. That's almost 1.5 amps of difference. If the laptop needs more power, and can't source it, the brick will either blow from overcurrent, or the laptop will shutdown.

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Well, I've done some reading on the adapter I bought, and it says that it has overcurrent protection, and it's safe from overvoltage and shortcircuting. My original AC adapter was a 90W with an output of 19v, and my new one is 65W with an output of 18.5v. On both adapters descriptions, they say that it's compatible with my laptop, an HP dv7. I'll also mention that for a week or so, I used my mom's HP AC adapter, which has basically the same specs as this one.

With that info, do you still see a danger? I'd really prefer not to have to send it back...

Ohm is right, you should get one with the same voltage and at least the same current (or power) rating. Otherwise you may be risking damage to you laptop.

Ah, I thought that it was safer to go with a lower power rating than a higher one.

You mention a broken wire on the old supply, can this be repaired?

I brought the old supply to someone who knows much more about soldering / wiring than I do, and he had a hell of a time trying to fix it. The break in the wire was very close to the power brick, which made it difficult to work with the wire. There was no easy way of opening the brick either. Also, apparently the cable was a triaxial cable rather than the usual coaxial one, which made it hard to keep the shit separate. That's what I got out of what he told me, anyway.

Did you make sure to match the center pin?

plug_types.gif

Often times the thing that causes the buzzing is incorrect polarity.

look around on your laptop for one of these symbols and see if it matches the power supplys one.

if not, you may need a correct one.

Edited by IndexPhinger
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If the polarity were wrong, it just wouldn't work. In fact, if there are no protection diodes in the power supply, any filtering caps may explode and voltage regulators can burn up.

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Yeah, the power brick gets pretty hot while the laptop runs and charges at the same time. If I remove the battery while running it, everything seems fine, though.

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