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Testing Laptop Components

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by casemaker

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I have a Compaq presario 1200XL that is dead. The laptop will not power on. The power cord is ok with green indicator light on adapter on. While it is plugged into the laptop the green led indicator for plugged in power is constantly on. I want to know how to test the system board, power supply and voltage controller board to confirm working and failed components. Please don't send me to compaq's help sites I have already been to most of them. I need specific help on testing the circuit boards.I dont have any problem inside the box I am a tech just no laptop experience other than field replacable parts.

14 replies

by qballrail

By and large, a laptop is merely a very compact desktop PC. All of my component testing has been done similarly to a desktop. Any good voltmeter is appropriate for testing any and all components. Although, you can obtain a memory tester through Fluke or other outlet as such for testing DIMM & SIMM vitality.

by qballrail

I don't know how much experience you've had with troubleshooting laptops, but I've had my share and they are not at all unlike a desktop with all the components integrated, such as the lower end models. Laptops are only smaller with some configuration differences and troubleshooting is not much different.

by qballrail

OOPS! Hit the damn tab key again.

It's all electronics, my friend, only on a smaller scale. To test individual components, you merely apply power to it and measure resistance or whatever you need to do with it. Sorry if this isn't much help, but questions like this are easier shown than described. I could write you a novel on it but not enough space provided.
To be honest, I learned the hard way.. was left to simply fix based on my previous experience with desktops. SO, I disassembled it, marking parts and setting them in order so I knew my way back when finished. It's a pains-taking process but if you just take it step-by-step, methodically, you will be able to do it. Once you get to the component(s) in question, slap a meter toit and test away.
The problem with laptops, however, is that there is even less to actually replace... one part goes bad, toss the entire board and get a new one, hence the phrase,"throw-away electronics." The components integrated onto the MB of a laptop are much too intricate to desolder and resolder.. it's all done by machines now. If you want to troubleshoot any drives, they are easy to remove. Usually the HDD is under a hatch while the CD is a little more difficult to get to. Power supply, just apply the meter to the + & - terminals (as it is DC once it passes the transformer).

by casemaker

The laptop components are very different from a desktop. For example how would I use the meter to check the power supply, the motherboard and the voltage controller. I need to determine which of these components are dead. With a pc I strip down to the motherboard with video/kb/ms and see if I get memory error so I know the board is good. I dont see how to do that with a laptop. I have never tested any components on a laptop, have only replaced field parts and troubleshot OS

by rcom

There are horror stories galore on the Compaq Community site where 1200XL laptop users are having the same issue.

So let's be frank, You need to have electronics troubleshooting skills and test equipment, at least a good multi-meter. Don't take this wrong, but if you had the experience you probably would not be asking these questions.

I don't know of many computer techs that actually test components and especially power supplies. A few will test for 12 and 5 volts. If not most will swapthe part out. If you could find a failing part the chances of finding a replacement would be rare.

A few simple tests you can perform with a meter;
Take out the battery, drives, etc see if the power comes up.
The fact that you're getting indicator lights doesn't mean that the AC adapter is good. Check the output voltage see if it's what it says on the rating label. If you've taken it apart the fuse is packaged different but it's located close to the power connector. Which should be checked for solder problems. I think the fuse is F101. Test it like any other fuse. There should be a short across it. Check the output voltage as compared to the input of the fuse to ground. They should be the same. The boards are multi-layered so the traces are very hard to follow, but you can try point to point testing and you may be able to find where the power is being dropped.

I have a vendor that repairs laptops and all the boards. They will only deal with computer companies. If you'd like more info on that email me at
rcom-services@qwest.net

By the way here is a Compaq site that has the part numbers I wouldn't get them from compaq as they have the highest prices.
Try RPC.com for parts.

http://www.compaq.com/support/Techpubs/qrg/presario1200xx.html

by richard_barsby

Hi I have fixed a number of these try to run without a battery installed I.E. just off the psu.

Do any of the other indicators illuminate during power on, if so for how long, the voltage converter board is in the middle with 3 coils on under sideit has 1 fixing screw 2 of the coils provide supplies for the laptop and the 3rd nearest the front for battery charging, you really need a scope to see if the coils are switching to provide supplies.

Best of luck

Rich

by zlitocook

I take it that you have tested all the flat cables and connectors? Where the power supply plugs into the computer is there any play? If so is there any dark places or discoloration? Lap top mainboards are multilayered you may not see a break in the connection. If it is compleatly nonactive I suggest sending in to a repair depot because most people do not have the proper tools and test equiptment to work on them.

by jmarraffino

Although I'm not familiar with your particular model, I work with Compaq laptops on a daily basis and it sounds like yours may be "stuck in standby" (Sleep or Hibernation). As one reply you received mentioned, you can remove the battery, drives, etc& try a/c power only to get it to boot. On some of the older models (7400, etc) we removed the battery & HD & booted. When we got a drive error message, we powered down, put the HD back in & it worked fine. You might also try holding down the power and sleep button (if it has one) at the same time for 10 seconds without any power applied then try to boot with a/c only. This has also worked on some of the M-series laptops from Compaq. Best of luck.
John

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