Gateway P-7805u no power/won't boot

I was just given a non-functional 7805 and I'd like to fix it up so I'm starting this thread because I think I'm going to need some help from you guys. I'm out of town and left the laptop at home so I can't troubleshoot it yet but I can tell you what I was told was wrong with it and hopefully when I get started on it I'll have a plan.

I was told that the laptop was taken to an IT store and they said the motherboard is "broken." So vague. I'll also tell you that the laptop will not power on.

I personally wasn't able to try anything except hitting the power button once before I left town. It wasn't plugged in and I still have to pick up the ac adapter, but I tried plugging in a universal ac adapter and it didn't light up the power led.

I read somewhere that I should check the cmos battery, so I'll replace that when I get home. I'd like to know what else I can plan to look at for when I get time to mess with it. My goal is to spend under $150 if it's even necessary to get this computer running again. If it can't be fixed for less than $150, I'm selling it for parts.

I was also told the screen doesn't work, but I don't know how so I'll have to save that one for later. I'm assuming that the screen is probably fine it just needs a new screen cable or the gpu was overheating.

I'll appreciate any tips and I'm really hoping to get this up and running again. I used to have a p-7811fx and I loved it. It miss the nvidia gpu sometimes, not even sure why. Wish me luck.

 

Update with bonus bump, just got home and will be able to mess around with the laptop starting tomorrow. If anyone is wondering anything about it as far as details let me know. I can now finally troubleshoot it further.

Peace

 

Don't quote me on this but I think I remember reading somewhere about some laptops using a magnet as a means of determining whether the lid is open or close. Might be something to look for.

Laptops aren't exactly my forte, but I once had a desktop with a problem powering on. Turns out it wasn't completing the circuit when the button was pressed. It was easy to use a multimeter to test if there was a current, I don't know how simple that would be on a laptop though.

 

That will definitely be one of the main things I look for once I get the power adapter. Hopefully I'll be able to pick it up tomorrow. Happy new year everyone

 

Bump

I finally got a power brick. It is the targus 180w universal and I am currently using it on my G73JH to type this message so I know the brick is fully functional.

Here is what happens when I plug the brick into the 7805, the brick shuts down and there is no activity on the laptop's power leds.

I can only assume/theorize that this means there is a short causing the brick to shut down. Can anybody tell me if replacing the DC jack on the 7805 would fix this, or is it more likely the entire motherboard? Thanks for all your help and patience. Took me long enough, right?

 

It could be an electrolytic capacitor on the main board that has shorted and the power brick is protecting itself from the huge current draw.

but I am just speculating here.

 

Well you can buy a new mini board for $35 on ebay, but who knows if it'll solve your problems. If that's not your problem, you'll be out $35.

eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

edit: I would probably disassemble the entire laptop first and put it back together. Maybe you'll see something.

 

I did a full disassembly a couple of weeks ago and all I found was that someone had left the CMOS battery disconnected. A test of the CMOS battery with a multimeter showed 3.3 volts, so that shouldn't be a concern at least.

Would I have noticed a shorted capacitor? I was looking for any capacitors that may have had a charred surface or slightly raised area on the top, and I didn't notice any. But I could always go back and look again, I may have missed something.

I admit motherboard repair or diagnosing really isn't a specialty of mine so there are a lot of things I could be missing. But if someone can think of a way I could test for things I'd be glad to try.

 

I bet that daughter board is the issue. Either that or the DC Jack is bad. If you aren't getting any lights on at the front, that would be my first bet. Without looking at circuits, I would bet that if a capacitor popped, it would be on that daughter board too.

 

I'll see your bet I'll try the DC jack first since it's cheaper. If that doesn't work then the daughter board would be next, and if that doesn't work, this 7805 will be dangerously close to being parted out.

 

You should be able to ring out the jack with a meter..and look for shorts?

 

Well I tried but since I don't know what I'm doing with a multimeter I couldn't figure anything out. If I knew how to use it and the manual wasn't in Engrish I would have kept trying.

A new DC jack is in the mail but for the sake of research I'll do any tests you can suggest once I have the laptop apart again. Just let me know what you think I should test and how if that's ok. Thanks

 

Well, you want low ohm settings. My Fluke is auto ranging but as long as it's reliable, NP.

Touch both your leads together, should read 0, you just read your first short!

What you want to do is use the low scale with a beeper if ya got it. Firmly touch middle pin, this is normally B+. Now look at back of connector and where soldered onto board. The idea is to wiggle connector pin and not have any make or breaks with you meter. The reading should be 0 with no floating around. This is basic and needs to be completed on B+ and return legs.

Reading caps, in circuit, is royal pain. Suspects are pulled and read for shorts, open and capacitance if your meter has it. Google how!

Power brick shuts down? If this is caused by shorted component, you have to find/isolate it. Hopefully you can carefully unplug stuff, like CPU ot isolate other items by unpluging. I would make a simple inline fuse, 5-6 amp to keep from smoking ur brick. This is dangerous as I know your limited here.

So, now your a TECH! Broken laptop, hey tech away..or look for flate rate repair or MB swaps.

 

I have to admit, I couldn't replace the DC jack. My soldering iron just isn't hot enough. It worked when I replaced a DC jack on a blackberry, which was a lot smaller. I guess this larger DC jack has thicker solder and my iron sucks

I'll have to just save up and buy the power board for $35. BTW I did some resistance tests on the old DC jack and the new one, and the results were the same (0.01) on the 20k setting if I remember right. I guess that means the DC jack is fine?

Wish I knew. I'll let you know what I find out and thanks for all the help.

 

Your resistance measurements are wrong, you have to measure from the outer sleeving of the jack to the middle pin, it should read high resistance (i.e. >1Mohm). For a short on the board it should read very low resistance (i.e. 0.01 ohms about)

 

Ah you are right. Good call I'll try that soon. Thanks

 

I bit the bullet and bought a daughter card on eBay today for only $23. I'll update you guys once I have it installed.

 

Slapped in the daughter card and the problem still exists. Plug in the power brick and the brick immediately shuts down. As someone said somewhere in this thread, there's a short in the mother-freakin-board. Waste of $23 but I just had to know. Now I know.

 

$250 later and a P79 motherboard has replaced the old 78 series board. Now the laptop boots as it should, but the screen backlight is out. I knew that could be the case going into the project though, so in a couple of weeks I'll pick up a new screen and be done restoring this FX. Looking forward to that for sure! Until then it's external monitor time.

 

Replaced the backlight and all is well. Replacing the backlight wasn't the most fun I've ever had, and I hope I never have to do it again. But now the laptop fully functions. Well, the hardware fully functions. The Windows 8 software is not quite so neat, going to revert back to 7 soon.

 

I just got the RTM of Win8 PRO. No aero looks strange. I can say that with the Bulldozer patc at least all CPU optimizaations now make it in an inplace upgrade. I had to revert right back though as I loose the HP software and need it for network scanning duplex to PDF. I am debating on a dual boot setup now.

I know the enhancements held as SuperPI went from 38 seconds to 36 seconds and 3DMark06 CPU went from 4535 to 4979. This is in line with the CP of Win8 when I did a seperate boot. At the time the patch was not in Win7 when I did the inplace upgraade so the enhancements were not in place.

I noticed too this time the system lost alot of snap. Programs seemed to take forever to open. then again I dod not have it long enough to let everything settle out. I really want to like Win8, it si just so hard...........

FYI with the RTM the side bar is GONE! It seems there is some hope with patches from server version. I'll have to explore them later too. I mis not have a constant monitor of my CPU and other goodies.

 

Tanware, everyone, well most everyone, is complaining that they can't do real work with win 8. You know spreadsheets, data base, word processor stuff, you know all the real apps that get things done. Have you found that to be true?

 

NO, you can put the needed programs in Win8 for office etc.. It is just a bit more awkward accessing them. Some associations default to the metro variant, like PDF. So you will have a bit to do there as well. Also the full start screen every time to start another program is a bit much IMHO.

So putting it in short; Win8 is as fully functional as Win7, slightly faster and more secure but much more awkward at times to get things done and move around. Expect, as with all new OS's, some driver issues at first................