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Why it's sometimes best to send a laptop to a shop for repair

By robo_dev ·
A co-worker who is reasonably handy, but with limited electronics knowledge, decided to try to repair a laptop for a girl-friend of his.

It's a just-out-of-warranty HP DV7, and the original symptom was the battery not charging unless the power cord wiggled just the right way.

Since the power jack is a separate replaceable $5 part on this model (which does not require soldering or motherboard removal), it would be logical to just swap the part. A twenty minute job at best

Of course what my co-worker did was first bought a new battery and power supply and when those did not help, he then attempted to swap the motherboard.

He then gave up and handed the project over to me.

When I got it the laptop would it no longer POST with the new motherboard installed. I took it apart and confirmed that although he DID damage the internal video connector cable, there were no obvious assembly mistakes, (although I don't know why he did not clean out all the dust with it all apart)

The replacement motherboard looked older than what was there, and he said the laptop owner bought a used one on ebay for $50.

Since it would not POST, my conclusion is either the replacement mobo is defective or it got zapped with ESD when assembling.

I put the old mobo back in and the laptop would POST, but no video. When jiggling the damaged internal video connector a small puff of smoke came from it...ugh...not good. On these models the little gumstick-size inverter board is in the display bezel, so the rather slender cable that carries the video signal also has the power feed for the inverter (thus the smoke).

Since it does put out video thru the VGA port, it appears the mobo is good and putting out video. The DV7 is well-known for the GPU not being soldered on properly, but I am assuming the video cable is the fault here.

Thus now I have on order the $24 video ribbon cable for the display and the $5 replacement power jack assembly.

I did make a mistake and ordered the wrong ribbon cable before opening up the display housing, (I should know better than to order a part without seeing the part number printed on the old part).

So now, six weeks later, once the correct replacement cable and jack comes in the mail, and assuming the display inverter board is good, it should (fingers crossed) all work properly, as long as something else like the inverter is not toast.

So the lesson here:

A reputable repair shop would have fixed this beast almost two months ago, and it probably would have cost less....on the workbench I have one $50 dead motherboard and a damaged $25 video cable.

Not to mention the purchase of a new power supply and battery, which was not really needed. (approx $80)

My only compensation is I asked to be taken to lunch at some point, assuming this laptop works when I am through with it.

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Follow UP: got the beast fixed

by robo_dev In reply to Why it's sometimes best t ...

After reassembly with new parts, noted that PSU was only putting out 12V, not 18V. Re-soldered power cable and it works like a champ.

In the end, basically the guy trying to fix it killed the motherboard and video interface cable whilst trying to swap the motherboard, while the real fault was, alas, the power supply plug (!).

Fortunately the replacement motherboard worked (and was needed) and I was able to swap video interface cable without destroying the big expensive display panel. Whew!

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