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Replacing eMachines T6420 motherboard

By Woodsman12 ยท 10 replies
Dec 22, 2011
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  1. Awhile back my eMachines T6420 blew some caps on the motherboard and quit working. I bought a new MS-7207 mb and a new power supply. It still won't work right. The computer powers on and off with the front power switch but I get no indicator lights on the front of the tower and a "No Signal" message on the monitor. The Caps lock and the Num lock lights on the keyboard don't light up and my optical mouse light doesn't come on. The cooling fan on the power supply and on the case run but the CPU fan is off. My DVD\CD tray will open and close but if I put the restore disc in it nothing changes.
    I would really like to get this machine running again so that I can rescue my files. I have an exterior hard drive I used for backups but since this machine I have now is a Win 7 version it refuses to recognize most of the backuped up data. Plus I really miss Outlook Express.

    Thanks for any help you can give me.
  2. dmill89

    dmill89 TS Guru Posts: 471

    It sounds like your new motherboard or powersupply may be bad. There is also the possibility that other components (CPU, RAM) may have been damaged depending how the old board failed. Was it just leaking caps or did it fail catastrophically (sparks, smoke, exploding caps, etc.)? Of course double check all connections and make sure all components are seated properly in their slots/sockets. Also what PSU did you get (is it OEM or aftermarket and if aftermarket please give brand, model, and rating on the various rails). Also was the "new" motherboard actually new or a used/refurbished one?
  3. Woodsman12

    Woodsman12 TS Rookie Topic Starter

    It just stopped in the middle of a silly game that I played many times before. I opened the case and noticed that the 5 3300mf 10v caps next to the CPU were domed. Tried replacing the caps, no luck.
    The power supply was an aftermarket ps that was supposed to be a new direct replacement. The mb supposedly was an unused MS-7207.
    How do I check the CPU, RAM and the hard drive without just replacing them?

    Thanks for the reply.
  4. dmill89

    dmill89 TS Guru Posts: 471

    hdd,cpu,ram are dificult to test unless you have spares or can try them in another computer. If you have more than 1 ram stick you can try them one at a time, also try disconnecting anything unnecessary (leaving only the MB, CPU, and RAM)and add components one at a time. What is the brand, model, and wattage of the PSU, and how many amps are one each rail(this info should be on the PSU's sticker)?
  5. Leeky

    Leeky TS Evangelist Posts: 3,357   +116

    Are the fans spinning up when you hit the power switch? The lack of display LEDs on the front of the case could well be due to incorrectly wired headers on the motherboard, so right now is nothing to worry about in that respect.

    Remove the side cover from the case, and then watching the motherboard area hit the power button. Does the CPU fan power up? Do the case fan(s) power up and spin?

    Are you using onboard or discrete graphics? e.g. are you connecting the monitor cable alongside the USB/ethernet ports at the top of the case, or connecting the monitor into a separate graphics card in one of the slots on the bottom half of the case?

    Also, when you replaced the motherboard, did all of the existing standoff's match the new motherboards mounting holes? Are there any still in place on the case that didn't line up with the new holes, and are therefore touching the reverse of the motherboard? If so, that would cause it to short out and therefore not power up.

    If you can, a couple of pictures of the inside of your case might enable us to see the problem if you have missed an important step.
  6. Woodsman12

    Woodsman12 TS Rookie Topic Starter

    When I power it up the case fan and the two ps fans run constantly. The CPU fan runs for a couple of seconds and then stops.
    It has onboard graphics, no separate graphics card.
    The standoffs match the old mb since the old mb was an MS-7207 K8NGM@ and the new mb is exactly the same.
    I have 2 128MB RAM and 2 1G Ram modules. I tried them one at a time-no change.

    I can't find an "attach" button so that I can post pictures. How do I do that? I've got a photo of the ps and one of the inside of the case.

    The new ps is a Logisys PS480D2 with a total Avg Output of 330W and total max output of 480W.
  7. dmill89

    dmill89 TS Guru Posts: 471

    I'm still thinking a bad motherboard or other major component however that PSU may be your problem. I've seen those PSUs personally and they are so light it's hard to believe there is anything in the box. Those are extremely overrated and may have trouble even running a low power system like this one. Have you tried disconnecting all drives, expansion cards, etc. and running it with the CPU/MB/RAM only? to see if you can even get it to boot to bios. Also did you remove and reapply thermal compound to the CPU? If you have access to another known working PSU I would try it and see if you can get the system to work.
  8. Leeky

    Leeky TS Evangelist Posts: 3,357   +116


    You can add them to the Picture Gallery, by following the link in the top blue bar of this page, or by clicking here. At the top right of the page that opens will be "Upload Picture" --use that to upload them, and then open the picture up and copy its address. Then paste them in this thread.

    I'll reserve further judgement until I've seen pictures, as it could be an installation issue.
  9. Woodsman12

    Woodsman12 TS Rookie Topic Starter

    I've tried running it bare boned and still have the problem. I removed the thermal compound and replaced it with new, expensive thermal compound. I think I will tear the thing apart again and check everything once more to see if I screwed up the CPU or have a short.

    Would you have any suggestions about a more powerful ps for this T6420? If nothing else I guess I could replace the ps with a more powerful one, get a graphics card (any suggestions?) to get around the integrated graphics.

    I'm going to try Leeky's tip about posting some photos.

    Just tried to upload a photo and I get an error message saying I have no internet connection. Will try later after I figure out what I'm doing wrong.

    I just finished disassembly, took out the CPU heatsink and the CPU. Under 20 power magnification I can see at least three pins that are bent. Does anyone know of a pin straightener device? My hands are too old and shaky to do it myself.
  10. dmill89

    dmill89 TS Guru Posts: 471

    I usually use a single edged razor blade, I'm not aware of any device that is specifically designed to straighten pins.

    If you need a new psu I would recommend this one:
    Antec Basiq BP350 350W =$30
    It's a rebranded FSP for less then what the FSP sells for itself. It is not particularly high power and is an old design but is definitely fitting for an older low powered system like the eMachines T6420 and is good quality, much better the Logisys.
  11. Woodsman12

    Woodsman12 TS Rookie Topic Starter

    Thanks for the help guys but after straightening the CPU pins, cleanup and reassembly,then still have the same problem I have decided to toss the T6420 and learn to live with Win7.

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