Laptop power adapter question

I have a Dell Inspiron 3800 (Dude your getting a Dell :biggrin: ) laptop in my hands at the moment. I just took it apart and cleaned it and put it back together (that was fun!)

But I dont have the power adapter for it and the batery if flat. I dont even know if the laptop works or not. But I was wondering if anyone knows a way to substitute the power adapter with something else (IE: making something homemade)

Thanks,

Wild Card said:
I have a Dell Inspiron 3800 (Dude your getting a Dell :biggrin: ) laptop in my hands at the moment. I just took it apart and cleaned it and put it back together (that was fun!)

But I dont have the power adapter for it and the batery if flat. I dont even know if the laptop works or not. But I was wondering if anyone knows a way to substitute the power adapter with something else (IE: making something homemade)

Thanks,

uhh, 12 volts dc perhaps.. i suggest, you look it google style though, might be a much better path to not frying it :biggrin:

ever once in a while, the plugin will have print beside it denoting its preferred power source.. look close

Some laptops have posh multi-pin connectors, but if it's fairly old, it could be just 12v dc as Orph says. You want to make sure this is correct before you try it though. Look on eBay for laptop power adapters and see what comes up - you may find somebody has given the specification.

I'm doubtful that this can work though. Not many plug-in supplies are going to be able to supply the current the laptop needs...

I would highly recommend NOT running the laptop with anything but a notebook power adapter. those things aren't simply adapters, they are the power supply just like in your desktop (or so I understand) They contain many active components that condition the power so that it can be used in the computer circuitry without burning something up or just causing erratic behavior.

You probably know more about this Jeff, but jury-rigging a power supply sounds like a very bad idea to me.

I'll see what I can do to find something. Orph, google didnt help. I searched for Dell Inspiron 3800 and didnt get a lot of valid information. And I cant buy stuff of the internet, but eBay has a nice selection of power adapters for 20 bucks. Too bad.

By the way, a quick ram question. It says

8Mx64, SDRAM
PC100 - 222 - 620

Does that mean its a stick of 512mbs? As well, what would be its speed? PC100 ram or what?

take a look at these, some different power adapters :smile:

No, that means you have a stick of 64Mb and the computer has 8Mb internal ram. Or at least that's how I remember it working on Laptops.

The speed is PC100, which is ... really slow. I can't remember the speed for that .... 64Mhz?

(As opposed to PC2100 being 266Mhz, PC2700: 333Mhz, PC3200: 400Mhz, and such for current ram speed examples)

Crono said:
No, that means you have a stick of 64Mb and the computer has 8Mb internal ram. Or at least that's how I remember it working on Laptops.

The speed is PC100, which is ... really slow. I can't remember the speed for that .... 64Mhz?

(As opposed to PC2100 being 266Mhz, PC2700: 333Mhz, PC3200: 400Mhz, and such for current ram speed examples)

Isn't it 100Mhz? Hence the "100" and 133 is 133MHz accordingly.

Um ... I'm trying to remember, I'd honestly would have to go find a stick of it and look at it to be sure.

But, probably. I haven't used them in so long. However, I know only the early SDRAM sticks read like that. SIMM doesn't, RIMM doesn't, and the newer SDRAM doesn't (DDR, DDR2, etc).

until they started the 4 digit system, the number after was the mhz hence pc66,pc100,pc133 were 66,100,133 respectively.

also each was one step backward compatible, you could put pc100, into a pc66 slot and a pc133 into a pc100 slot. the chip would dummy down one speed without burning out.

the new chips, i don't quite know about yet, since only one of my comps utilizes the chip.. but i will learn, eventually :smile:

awesome. Damn lol I though you had to multiply 8 with 64 to get the ram, I was like w00t!!! 512mbs :biggrin: Maybe not.

I'll see if my coop placement has a power adapter for the laptop. I know a place that sells them for 75$ (store about 5minutes away from my house) but I dont want to buy it for 2 reasons. Its damned expensive, eBay sells them for 20$. And B) I dont know if the laptop works or not since I have not yet tried it. The batery isnt charged and I have no means of power.

Orpheus said:
until they started the 4 digit system, the number after was the mhz hence pc66,pc100,pc133 were 66,100,133 respectively.

also each was one step backward compatible, you could put pc100, into a pc66 slot and a pc133 into a pc100 slot. the chip would dummy down one speed without burning out.

the new chips, i don't quite know about yet, since only one of my comps utilizes the chip.. but i will learn, eventually :smile:

...only if all of them were the same frequency. And a lot of times that didn't work, a motherboard had to support that option ... so just because you had board that supported it doesn't mean it was a universal thing... I've had plenty of board that don't support that feature.

WC, just go to the store, present your problem, and I'll be very suprised if they don't crack open a package and let you try the adapter in the store.

Orph is exactly right, but on top of that, PC133 works in a system that started with PC66. All Simms and Dimms were totally backwards compatible. Even if you had a 66MHz simm and wanted to put it in a system with a 100MHz FSB, you could usually just increase the CPU multiplier while decreasing the FSB to let the memory work while keeping a similar core clock (of course it would not perform as well due to the slower memory).

512 is right WC, 512 is the number of bits in the memory. 8M * 64 is how the memory is phyiscally arranged, 8 million rows of 64 bits per row (memory is 64 bits wide, read 8 bytes in one cycle).

Tracer Bullet said:
WC, just go to the store, present your problem, and I'll be very suprised if they don't crack open a package and let you try the adapter in the store.

I asked to look at it. Plug doesnt fit inside the laptop. The power adapter wasnt new, it was a second hand thing made by Dell, but it didnt specify what model it was for.

I have searched the websites of local stores (Staples business depot, Radio Shack, Future Shop) and they dont carry anything. Radio Shack carries a universal power adapter that would fit, but its a 130$

eBay has some, but I have no way of buying over the internet.

here's a picture of the power adapter:


And batery:


Do you think there's any way of gerry rigging some AC adapter to fit the job?

[edit]
On the bottom of the laptop there is a sticker that says:
INPUT: 20V ____ 3.5A
................- - -

Sure, as long as you are using that dell power converter and just doing something to wire it to your laptop it should be fine. The issue is that you need that well-conditioned output from the converter. You should not however, try to wire the power converter directly to the battery. Li-Ion batteries have some sophisticated electronics that prevent them from being over-charged and subsequently failing catastrophically (explode). I don't know whether all of this is included in the battery or if some of it might be in the computer. So, if you do anything, you should wire the converter to the input on the computer rather than trying to set it up to charge the battery directly.

If you can find an adapter that can supply 3.5 amps at 20 volts, and you are sure of the connector polarity, there's no reason why it won't work. The 12 volts in a laptop is only used for motors (and perhaps the screen somehow) anyway, anything that needs a very clean supply has it's own regulator (5V, 3.3, 1.5, etc).

I still don't think you will find such a supply for any reasonable kind of price though. Do you have a friend who is able to buy from eBay? This really does seem to be the only cost-effective way of powering the laptop up.

scary_jeff said:
If you can find an adapter that can supply 3.5 amps at 20 volts, and you are sure of the connector polarity, there's no reason why it won't work. The 12 volts in a laptop is only used for motors (and perhaps the screen somehow) anyway, anything that needs a very clean supply has it's own regulator (5V, 3.3, 1.5, etc).

I still don't think you will find such a supply for any reasonable kind of price though. Do you have a friend who is able to buy from eBay? This really does seem to be the only cost-effective way of powering the laptop up.

I can get a 20V AC adapter at coop. Im not sure about its amperage though. I'll talk to some folks and see if they can get me something off eBay somehow. We'll see I guess.

Jeff, what do you mean about connector polarity, IE: pos, neg, and ground?

Think of your normal DC connector like a phone charger. Some have the outer metal as ground, some the inner. Get it wrong = melt :smile:

If you can't get it working, it goes in the bin, right? So you could parallel up two of these 20V things you can get if one isn't enough.

scary_jeff said:
Think of your normal DC connector like a phone charger. Some have the outer metal as ground, some the inner. Get it wrong = melt :smile:

If you can't get it working, it goes in the bin, right? So you could parallel up two of these 20V things you can get if one isn't enough.

me = confused :biggrin:

Connect the grounds of two of these adapters together, as well as the +20V. This should let you draw double the current. There's always the chance it will destroy something though, that's why I asked if this laptop will be thrown away anyway if you can't make it go.

sniff sniff I smell burning metal and plastic coming ...

Crono said:
sniff sniff I smell burning metal and plastic coming ...

Not quite. I went to a computer dealer (actually just some house litered with old computer parts on the floor), he gerry rigged a power adapter for me (at a cost of 79$) and then he tried it on the laptop. The end result was that the screen is br0ked. Since I had left him the laptop last night, and got it this morning I didnt see exactly what it looked like. But since the screen was br0ked, I didnt have to buy the power adapter (me save money :biggrin: )

After that I went to coop, and managed to scavenge a Dell power adapter. Its rated voltage is 18.5V with an amper of 3.8A However the laptop requires 20V with an amper of 3.5A

Now, the plug fits, and it is a Dell laptop certified for my model, the question is, will these differences do anything?

I want to try the laptop using a monitor, since Im sure that since the LCD screen is dead, the video out plug wont be. lol. I've already pluged the hard drive into my computer and it works. So Im pretty sure that the only thing dead on the laptop is the screen. I was told its 140$ to fix the screen, which is worth it considering the specs of the laptop. I just need to confirm the screen is the only broken part. BUt to do that, I need power, so I need to know if the Dell power adapter is good even though there are voltage and amper differences. (Is it even called amper? lol)

Europeans generally say ampere, but I think the international standard nomenclature is now just "amp" meaning 1 coulomb/sec.

Attaching a power supply that has a lower voltage rating will not damage anything. The fact that it is rated to more current does not matter. You would only have to worry if you were supplying a higher voltage than recommended. However, it might not be enough to power up the computer.

So it wont do physical damage, just might not power the computer? Well, doesnt the power charge the batery which then powers the computer?

Wild Card said:
So it wont do physical damage, just might not power the computer?

Correct.

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<TD style="FONT-SIZE: 11px; COLOR: gold" bgColor=black>? posted by Wild Card</TD>
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Well, doesnt the power charge the batery which then powers the computer?

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The battery is charged in parallel with running the computer, not in series as you are suggesting. You could run the computer without a battery in it.

Well I've given it a start. Its charging the batery, but I cant yet turn on the computer. It will turn on and then off 5 seconds later.

What happens if you take the battery out?

it sounds as though maybe you don't have enough voltage to run the computer, but you ought to be able to charge the battery and then use it as you are already trying.

Seems very unlikely to me that the 18.5 could cause a problem. Nothing in the laptop itself uses 20V, and most things should work with + or - 10% anyway.

It could be that the battery is charging, but no longer holds charge for any useful amount of time. If this is the case, I don't see why it wouldn't work with the battery out.

Noda, I took the batery out and turned on the laptop. The lights blink for about 8 to 10 seconds and then the laptop powers down.

Originaly it had 64mbs of PC100 ram in DIMM A. I now have 128mb PC100 in DIMM A and 128mb PC133 in DIMM B. Would that cause a problem?

Hey is the laptop's cooling fan supposed to always be on, or does it only turn on at a certain temperature? Because the fan is pluged in but not on.

If a simple voltage divider is being used to step down the potential, then a lower input potential would translate to a lower output potential. So if your conversion usually goes:

20 --> 1.5 V

Then changing the input would produce:

18.5 --> 1.39 V

I suspect there are detectors in the computer that shut it down if the potentials are wrong, although that is only a 7% difference...

/edit

Typicaly laptop fans only turn on at a given temperature; energy hogs that they are.

/edit 2

You might try testing your converter to see if it really outputs 18.5 V.

lol cause this laptop's getting quite hot and the fan aint on. Then again I've never operated a laptop...

I got it turned on. its because of the ram I had changed.

Man, I hated using Amper's law (when I had Physics). I don't really know why though.

laptops do get very hot, sometimes too hot to comfortably to use on your lap sorta defeating the purpose of a laptop :razz:

The laptop I had would get very hot even though the fan was on :\

Possibly, the fan isn't working properly ... or your battery sucks ass (<- most likely the case).

So it works now?

All the voltage rails in the laptop will either use their own switching supply on the circuit board, or at the very least a constant voltage regulator. Even the simplest of regulators include simple feedback so that the output voltage doesn't depend on the input (assuming it's within a certain range obviously).

Well, originaly, the screen was busted. And I was unsure about the fan. So I opened up the laptop again, and the fan was pluged in. I downloaded a Dell Diagnostic disk and ran a test on the fan and it worked. I was just worriing too much

But at the asme time, I got the screen working somehow. Now everything works. The hard drive is a little beat up with bad sectors but it still works. Will do a Windows install today. Or maybe Linux. Not sure.

Well, originaly, the screen was busted. And I was unsure about the fan. So I opened up the laptop again, and the fan was pluged in. I downloaded a Dell Diagnostic disk and ran a test on the fan and it worked. I was just worriing too much

But at the asme time, I got the screen working somehow. Now everything works. The hard drive is a little beat up with bad sectors but it still works. Will do a Windows install today. Or maybe Linux. Not sure.

scary_jeff said:
So it works now?

All the voltage rails in the laptop will either use their own switching supply on the circuit board, or at the very least a constant voltage regulator. Even the simplest of regulators include simple feedback so that the output voltage doesn't depend on the input (assuming it's within a certain range obviously).

Ah, that makes snense...

I really ought to learn more about computer architecture.