Emachines T5088 - CMOS/checksum random errors

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  • caphair
    Badcaps Legend
    • Nov 2011
    • 1249

    #1

    Emachines T5088 - CMOS/checksum random errors

    I'm trying to fix this PC for a neighbor and originally the complaint was it randomly shuts off and/or turns itself back on.

    First I suspected it was overheating as the CPU fan would get noticeably louder during processing. So cleaned any dust out (which was hardly any) and replaced original thermal compound from to CPU to heatsink.

    That seemed to help by 50% as the fan didn't get as loud but it'd still ramp up to annoying quick levels during installations or virus scanning.

    Had it running for a bit and didn't turn off. Wake up and it had tried to do a Windows update and was stuck on a screen saying repairs couldn't be made and to restore to a well known part.

    All the while in between these issues it'd randomly give a cmos battery failure followed by checksum failure error during boot. Battery was tested 3.08v but replaced anyway to see a change, none same messages.

    However it wouldn't be a consistent issue. I tried resetting all bios settings which seemed to have worked but when the PC was unplugged for literally a minute the same CMOS errors came back.

    Not sure if all the issues are related. No visible bulged caps on the board.

    Imo the PC isn't even worth all this trouble but she needs it and I'm trying to help so any input would be appreciated. Thanks!
    Last edited by caphair; 10-21-2015, 06:13 AM.
  • stj
    Great Sage 齊天大聖
    • Dec 2009
    • 30977
    • Albion

    #2
    Re: Emachines T5088 - CMOS/checksum random errors

    Emachines have a very bad rep for failing psu's
    check the psu inside for burst caps.

    Comment

    • pfrcom
      Oldbie
      • Jun 2006
      • 1230
      • Australia

      #3
      Re: Emachines T5088 - CMOS/checksum random errors

      Run a few passes of MemTest86+ to verify memory's integrity
      better to keep quiet and be thought a fool, than to open your mouth and remove all doubt

      Comment

      • caphair
        Badcaps Legend
        • Nov 2011
        • 1249

        #4
        Re: Emachines T5088 - CMOS/checksum random errors

        Should I check PSU for bad caps before running memory test or doesn't matter?

        Comment

        • SteveNielsen
          Retired Tech
          • Jun 2012
          • 2327
          • USA

          #5
          Re: Emachines T5088 - CMOS/checksum random errors

          I'd check the PSU first.

          Comment

          • stj
            Great Sage 齊天大聖
            • Dec 2009
            • 30977
            • Albion

            #6
            Re: Emachines T5088 - CMOS/checksum random errors

            if you cant trust the psu, every other test is meaningless - so psu always comes first.

            Comment

            • caphair
              Badcaps Legend
              • Nov 2011
              • 1249

              #7
              Re: Emachines T5088 - CMOS/checksum random errors

              True. Do bad caps give wavering voltage or low outputs if measured or no?

              Comment

              • stj
                Great Sage 齊天大聖
                • Dec 2009
                • 30977
                • Albion

                #8
                Re: Emachines T5088 - CMOS/checksum random errors

                bad news for you, the emachines psu's are known to have the voltages RISE as the caps fail - specially the 5v standby!!!

                Comment

                • stj
                  Great Sage 齊天大聖
                  • Dec 2009
                  • 30977
                  • Albion

                  #9
                  Re: Emachines T5088 - CMOS/checksum random errors

                  http://www.techspot.com/community/to...his-now.62782/

                  Comment

                  • caphair
                    Badcaps Legend
                    • Nov 2011
                    • 1249

                    #10
                    Re: Emachines T5088 - CMOS/checksum random errors

                    Yikes! I'll check that PSU out. Never did like emachines. Even their monitors aren't that great in terms of longevity

                    Comment

                    • stj
                      Great Sage 齊天大聖
                      • Dec 2009
                      • 30977
                      • Albion

                      #11
                      Re: Emachines T5088 - CMOS/checksum random errors

                      i think they are BESTEC psu's!

                      Comment

                      • caphair
                        Badcaps Legend
                        • Nov 2011
                        • 1249

                        #12
                        Re: Emachines T5088 - CMOS/checksum random errors

                        Ok I swapped in a similar rated PSU that I had and still get the cmos/checksum error

                        Comment

                        • kaboom
                          "Oh, Grouchy!"
                          • Jan 2011
                          • 2507
                          • USA

                          #13
                          Re: Emachines T5088 - CMOS/checksum random errors

                          Originally posted by caphair
                          Ok I swapped in a similar rated PSU that I had and still get the cmos/checksum error
                          Time to check/replace mobo caps. Take some pix and upload them.

                          Do not let it error out and attempt to recover/reflash the BIOS at this point, unless you want a bricked motherboard!

                          Take your meter (you do have one?) and check the purple wire. Should be no more than 5.25V. Not all bestecs have run away 5VSB.
                          Last edited by kaboom; 10-21-2015, 01:04 PM.
                          "pokemon go... to hell!"

                          EOL it...
                          Originally posted by shango066
                          All style and no substance.
                          Originally posted by smashstuff30
                          guilty,guilty,guilty,guilty!
                          guilty of being cheap-made!

                          Comment

                          • stj
                            Great Sage 齊天大聖
                            • Dec 2009
                            • 30977
                            • Albion

                            #14
                            Re: Emachines T5088 - CMOS/checksum random errors

                            did you check the voltage on the old supply?
                            incase it trashed the mobo.

                            Comment

                            • caphair
                              Badcaps Legend
                              • Nov 2011
                              • 1249

                              #15
                              Re: Emachines T5088 - CMOS/checksum random errors

                              Thanks I'll take some pics when I get a chance.

                              I'm curious about something, the PSU I used to test had lower amp ratings on the +12v and the 5v standby. The ratings were lower by 2 amps on each rail. Would it cause any problems using that PSU?

                              Comment

                              • caphair
                                Badcaps Legend
                                • Nov 2011
                                • 1249

                                #16
                                Re: Emachines T5088 - CMOS/checksum random errors

                                Originally posted by stj
                                did you check the voltage on the old supply?
                                incase it trashed the mobo.
                                No I'll do that too. I had 10 min free time today so swapped the PSU I had just to see if the cmos error would still come up.

                                Comment

                                • stj
                                  Great Sage 齊天大聖
                                  • Dec 2009
                                  • 30977
                                  • Albion

                                  #17
                                  Re: Emachines T5088 - CMOS/checksum random errors

                                  Originally posted by caphair
                                  Thanks I'll take some pics when I get a chance.

                                  I'm curious about something, the PSU I used to test had lower amp ratings on the +12v and the 5v standby. The ratings were lower by 2 amps on each rail. Would it cause any problems using that PSU?
                                  no idea unless you give the actual ratings and what's in the machine.

                                  Comment

                                  • caphair
                                    Badcaps Legend
                                    • Nov 2011
                                    • 1249

                                    #18
                                    Re: Emachines T5088 - CMOS/checksum random errors

                                    Here's a general over view of the board. Let me know if you need closer pics of a specific area. No caps look bulged and noticed there are two types used KZG and Rubycon.

                                    Also note, if the power cable is disconnected that's when it gives the cmos error, but if I set the date/time and leave it plugged in, it'll boot fine without the error.

                                    Do pcs only use the cmos battery when it's completely disconnected from power? Thought the cmos was in use even when it's been shut down.

                                    Also measured voltages of original PSU:
                                    5vsb - 5v
                                    12v - 12v
                                    5v - 5.25v
                                    3.3v - 3.40v

                                    I have a question about PSU ratings, if you're trying to swap one do you go by total output power or go by total amps rating on each rail? For example say you have two different PSU both rated at same max output power but each rail has an amp or two less rated than original. Would it be a safe replacement?
                                    Attached Files
                                    Last edited by caphair; 10-22-2015, 05:44 AM.

                                    Comment

                                    • stj
                                      Great Sage 齊天大聖
                                      • Dec 2009
                                      • 30977
                                      • Albion

                                      #19
                                      Re: Emachines T5088 - CMOS/checksum random errors

                                      your question, look at the amps, the W rating is often lies.

                                      Comment

                                      • momaka
                                        master hoarder
                                        • May 2008
                                        • 12170
                                        • Bulgaria

                                        #20
                                        Re: Emachines T5088 - CMOS/checksum random errors

                                        The only Bestec PSU that has a problem with high 5VSB is the ATX-250 12E. Another one (possibly) is the Delta DPS-300AB-15B - I haven't dug deeper into that one yet, though.
                                        (Anyways, if you have any such PSU and you don't want to fix them, send a PM to everell - he does like to fix the Bestecs. Or if you are in NoVA, Southern MD, or near Wash DC, let me know. I'll take an OEM unit and recap it any day over those cheap junk found in the stores).

                                        The other Bestecs (ATX-250 12Z, ATX-300 12E, and ATX-300 12Z) are well-designed PSUs. However, they do often still have bad caps in them which can make the PC do bizarre things or not work at all.

                                        However, it is not only Bestec that has problems. Delta/Newton and LiteON also often have bad cap brands inside them. So it doesn't matter what you have - just open it and check the caps. Those OEM units are actually really good in terms of built quality, sans the caps. Whatever you do, don't go buying a cheap sub-$20 PSU on eBay/newegg/Fry's... etc. The cheap PSUs can sometimes perform worse than the used OEM units, despite being brand new.

                                        Now to address some of your issues...
                                        Originally posted by caphair
                                        No caps look bulged and noticed there are two types used KZG and Rubycon.
                                        KZG are absolutely terrible caps and they can often fail without showing any visible signs. I just had a motherboard pop one KZG cap after sitting in storage for a year without any power applied. That's how bad KZG is - they can go bad all on their own!

                                        Other than that, I don't see anything else wrong with the board.

                                        If the CPU fan is getting really loud, check the temperature in BIOS after running the PC for about 30 minutes. You can also check the temperatures within Windows. Programs like SpeedFan are good for that. Maybe post a screenshot, too.

                                        Originally posted by caphair
                                        I have a question about PSU ratings, if you're trying to swap one do you go by total output power or go by total amps rating on each rail? For example say you have two different PSU both rated at same max output power but each rail has an amp or two less rated than original. Would it be a safe replacement?
                                        If it is just an amp or two on each rail, that's probably okay.

                                        However, the numbers on the sticker don't mean anything if the power supply is a cheap-o one. Cheap power supplies are well known to have overblown specs on their labels. So if you are not sure what you have, post the brand and model here so we can tell you if it's any good (or ultimately, post pictures of the inside of the power supply - then we know 100% what is going on ).

                                        One final remark I'll make about replacement PSUs is that these days, modern computers use power mostly from the 12V rail. So you really want the 12V rail to be capable of at least 14 Amps.
                                        A more scientific approach is to see what CPU the PC has and look up its TDP (Thermal Design Power) at http://www.cpu-world.com/
                                        Anything up to 90 Watts TDP will run okay on a PSU with a 14 A rating for the 12V rail - provided the PC doesn't use a dedicated video card. If the PC has a dedicated video card, then you have to take that into account as well.

                                        Which brings me to the point of how many Watts the PSU should be capable of...
                                        **In general**, 250 Watts is enough for a basic system with a CPU and onboard video card. If the CPU is a high-power one and there is an entry-level dedicated video card, you would probably want something closer to 300 Watts. If the graphics card is mid level, 300-350 Watts would be better. Again, that is a *general* guidline. Some PSUs can have a really high Wattage rating but unsatisfactory Ampere rating on the 12V rail - you don't want those. So you really have to look at both.

                                        Originally posted by caphair
                                        Do pcs only use the cmos battery when it's completely disconnected from power?
                                        Yes, only when PSU is unplugged from wall.

                                        You said you tried a new battery and CMOS still resets. In that case, also check battery socket joints. Bad caps likely won't cause this issue, because the battery power probably doesn't go through any electrolytic caps at all.
                                        Last edited by momaka; 10-22-2015, 10:22 PM.

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