Wednesday, June 1, 2011

Sometimes it's something else

Earlier today I got my hands on an older Compaq M2000.  It was dead, no lights no anything. So checking the board (which is the same as the V2000 and the DV1000) . The front end MOSFET next to the power jack had bubbling on the surface (probably from overheating) And it was the wrong chip!? It was a SI4425 which has a lower current rating.  So I replaced it with the AO4413/FDS6679 series and tested again.  This time the charge light was on when the battery inserted. This told me that at least the unit was getting power. Then I remembered the common problem with caps on those models, so I started checking the caps. Sure enough I found the shorted cap on the bottom side near the rear of the DVD drive connector. OK replace that and turn on.

Everything lights up, except the screen. No display on external. Hmmm - checking the GPU accidentally by touching it was !!HOT!! Used the crayon test, it made a small wax puddle on the chip. This GPU was definitely shorted.  When angling the board and viewing, I noticed the GPU was not level. Rear solderballs were not touching board, but the front solderball were. There was no level gap around the GPU.  So this came to a decision to set it aside and work on it later, or attempt leveling GPU.

I placed it aside and chose to make that a project because it would need a jig to level the GPU while hot, and not contact (nor slide) resistors on the top side. As well as raising the smashed side.While holding the GPU down onto the jig. Strange device it would be. But to fix a $66 mobo? Reballing is an option but not worth the money, time and effort right now.

19 comments:

  1. thank you for the help and your greatest blog. i have a hp compaq dv6735 which when i plugin the dc connector and push the pwr botton, the power ring flash for 7-8 times and don't run, the same with the battery. regards

    ReplyDelete
  2. dear, excuse me for the another question: how test the smd caps of notebook matherboard??? thanks thanks.

    ReplyDelete
  3. how i can donate same dollars for your blog????

    ReplyDelete
  4. Fransanos: SMD caps function the same way as ceramics, using a small lead on the meter check to see if there is resistance one way, and infinity the other. If you are showing zero resistance in both directions it is shorted.

    On the flashing ring light, that actually should not happen, nor can I assume why it would happen. The light will come on if the jack is disconnected from the motherboard.
    So one can assume it is a bad power supply, either wrong voltage, or current.

    There should be a donate button under the Shoutbox. Donations are welcomed and the contributions goes to PoorTechs of America (me). Just kidding but they are appreciated.

    ReplyDelete
  5. thnk you thank you so much. the resistance for ceramic caps muste be infinity or more low???and the ohm must be x1 or x10 or x1k or x10k???

    ReplyDelete
  6. Frasanos: It should be ok to test them in the 1x mode, or in the diode mode. That should give you a better indication if it is shorted or not.

    Backing up a little to your first post, I'd like to ask if you have checked the CMOS battery? When the system starts it reads BIOS setting from CMOS where it is stored when saved. If it cannot read, it will continue to attempt. After a number of failures it will shut down. The battery should read at least 2v.

    ReplyDelete
  7. hello Dr.Mayo, i feel very lucky as a new laptop tech in training to find your blog.(over 40 and changing career)could you mention some common mosfets you keep on hand. (relating to no power / dead issues)

    ReplyDelete
  8. thanks for your help. the battery was ok. the problem was the ac adaptator.
    Now run but the light of bloc caps do 5 lamps and no screen....is the mainboard problem for hp (hp 6735s). bad think.
    For the caps; in the x1 ohm mode i must have in one way infinity read and other ??? becouse in many caps i have two reads: one 0 ohm and second depend of caps...i use a analogic multimeter. tanks do much

    ReplyDelete
  9. mahatam: that info has already been covered. You may want to use the search tool on the side, or start about Jan 2011 when I started detailing parts better.

    Fransanos: I cannot answer every question, often discovery and experimentation leads to knowledge. Especially when several thousand start with specific models, and "How do I repair this..." That would take the fun out of showing what I'd like to share. As well as burn me out.

    ReplyDelete
  10. Fransanos: your last post, it may be a GPU problem. That model is known for the bad GPU/Southbridge no video issue. Also include series models, there is a 6735 as well as DV6735. It confused me for a minute.

    ReplyDelete
  11. i thought me too, but the strange think is that just he run the screen flash than immediatly shout down. the hdd lights continued to lamp and bloc caps flash for five...i know that i will win...

    ReplyDelete
  12. Dr.Mayo thank you for helping with the mosfets question.I spend many hours a week searching for datasheets to mosfets and other components, it's part of my responsibility if i want to be a good tech. I came across a great site for DataSheets that your readers might be interested in. WWW.digchip.com

    ReplyDelete
  13. mahatam: Another datasheet site that may come in handy is www.alldatasheet.com. I practically live there. :)

    ReplyDelete
  14. Thanks corrective, looks like another good site i can bookmark.

    ReplyDelete
  15. i follow ur blog ur awesome and im not sure if this is the right place to post this but since im not exactly sure how to ask a question on here i have a issue with a compaq presario v5000 no power no lights nothing,took apart 2 of the mosfets on top near cpu are fried there pq28 an pq25 tops of fets completely burned away i have no idea what to replace them with any help would be so appreciated thank you for hearing me out

    ReplyDelete
  16. I don't have one of the boards handy, but it should be 4 of them total in that area. The other 2 matched pair is the same. Usually FDS6676 can be found on the Fairchild site- http://www.fairchildsemi.com

    ReplyDelete
  17. dear, do you know which caps there are on the mcp67d-A3 nvidia chip???thanks

    ReplyDelete
  18. Sorry frasanos, I don't fix GPU chips per se, only the motherboards.

    ReplyDelete
  19. Hi mayo,
    i have reflowed the gpu and memory on an geforce go6800 graphics card from an Fuji M3438g laptop using liquid flux and the card is ok for a few days then it is back to the blocks of colour on the screen, i am flowing the memory on an temperature of 260 on each chip on both sides for about 60sec but it still wont hold the picture, i can do it as many times as i want and still the same result, any ideas as to what im doing wrong, i was hoping to have the DVD by now to get some more tips but will ask here also.
    Thanks
    Mike

    ReplyDelete

I cannot repair laptops for you via the internet, I can only answer questions related to posts. This is because I have not had experience on every motherboard that is out there. Bear with me.

If you do need it repaired. Contact me for quote (US/CDN Only)

Note: Only a member of this blog may post a comment.