Bad Ceramic in a Dell 390SFF PSU

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • cruzinforit
    Rin is my waifu
    • Apr 2015
    • 22
    • USA

    #1

    Bad Ceramic in a Dell 390SFF PSU

    This thread is also over at JG, I just posted it and don't feel like reposting it over here. We have a lot of these SFF PSUs fail the same way, this little Ceramic blows with a snap crackle and pop. Wonder what's causing them to blow.

    http://www.jonnyguru.com/forums/showthread.php?t=12806
  • linuxguru
    Badcaps Legend
    • Apr 2005
    • 1564

    #2
    Re: Bad Ceramic in a Dell 390SFF PSU

    That's the capacitor in the primary-side RC snubber for the main MOSFET switch. It has to be low-ESR as well as have a good surge voltage spec. If not, it will likely overheat and eventually fail. If possible, it should be replaced by an X7R or X8R ceramic with decent voltage specs (at least 1 KV or higher).

    Comment

    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 31213
      • Albion

      #3
      Re: Bad Ceramic in a Dell 390SFF PSU

      i have talked extensivly about these shit psu's a long time ago here.

      the cap is 1kv and needs to be 2 or 3kv to survive.

      if it fails your in for a world of pain, the cap, the fet, the fuse, the fuseable resistor, the controller i.c. on the sub-board and a shitload of smd resistors are gonna smoke.

      Comment

      • cruzinforit
        Rin is my waifu
        • Apr 2015
        • 22
        • USA

        #4
        Re: Bad Ceramic in a Dell 390SFF PSU

        Originally posted by stj
        i have talked extensivly about these shit psu's a long time ago here.

        the cap is 1kv and needs to be 2 or 3kv to survive.

        if it fails your in for a world of pain, the cap, the fet, the fuse, the fuseable resistor, the controller i.c. on the sub-board and a shitload of smd resistors are gonna smoke.


        Do we happen to know if the 80plus gold variant (H240ES) of these has the same problem?

        Comment

        • stj
          Great Sage 齊天大聖
          • Dec 2009
          • 31213
          • Albion

          #5
          Re: Bad Ceramic in a Dell 390SFF PSU

          no idea,
          all the ones i'v seen are H240AS

          Comment

          • cruzinforit
            Rin is my waifu
            • Apr 2015
            • 22
            • USA

            #6
            Re: Bad Ceramic in a Dell 390SFF PSU

            Hmmm. I took one of the units to be trashed because of a bad motherboard, and replaced the motherboard. I had ordered a new capacitor for it. But then I realized this is an 80plus gold unit, the H240ES. I want to make sure to fix it pre-emptively if it's still a problem, since I'm using it now as my HTPC.

            Comment

            Related Topics

            Collapse

            • Bowline
              Dell E6400 PT434 type Battery Charging Stuck at 1%. Battery Pinouts?
              by Bowline
              My question pertains to understanding the control circuity inside a Dell PT434 type battery used in Dell E6400, E6410 and other Dell notebooks?

              Does anyone have a circuit diagram for the inside of a Dell PT434 battery and/or a description of how the control lines work to control this battery?

              My reason for asking is I have a battery which I cannot get to charge beyond 1% in a Dell E6410 or E6400.
              The LED bar graph charge indicator on the battery shows one LED lighted when the info button is pressed.
              I have tried multiple different Dell power adapters. My Dell...
              06-11-2025, 10:13 AM
            • Akhlz001
              Dell Pro 13 Plus PB13250 Bios Unlock
              by Akhlz001
              Hi,

              Could someone help trying to unlock this BIOS, seems that Dell have changed the layout of new Dell Pro 8FC8 bioses from checking HXD - 4000 bits do not need changing, only 2000. However after FF the section starting from '01000' upto 2000 bits and then soldering the chip back it seems that the microchip on the motherboard is recovering the bios back to original settings after first boot. Has anyone found a way to crack this extra layer of security Dell have implemented? Seems both HP and Dell have upped bios security to match Lenovo by implementing extra measures on a separate...
              09-20-2025, 07:15 PM
            • master3112
              Dell Inspiron 5590 Board 18778-1 no charging, charging not possible
              by master3112
              I would like to share my experience about charging issues with Dell power supplies with the tech community. I am working on a Dell Inspiron 5590, Mainboard 18778-1 with charging problems. The device can be switched on and works so far, only the message appears at startup:

              Alert! The AC power adapter wattage and Type cannot be determined. The battery may not change. The System will adjust the performace to match the power available.

              The power supply unit is not recognized in the Bios and the charging process is set to "idle". I use original Dell battery, type...
              07-29-2025, 01:55 PM
            • SMDFlea
              Dell Thunderbolt Firmware
              by SMDFlea
              Dell thunderbolt firmware, extracted from dell firmware update exe. Padded to 1MB.

              Some models have a choice of 2 different firmwares, it depends on the dell SKU.
              The SKU is in brackets (****)

              EDIT: NVM65...
              01-26-2025, 06:22 AM
            • F R 2568
              Dell Latitude 5420 does not start (no post) need help to find the reason why
              by F R 2568
              Hello all,

              this is my first post, so if I make mistakes please do not hesitate to point them out, thank you in advance.

              I got a Dell Latitude 5420 (Service Tag: 7RFM6D3, Motherboard: GDF40 LA-491P Rev.: 2.0 (A01)) which does not start and I want to repair it. These are the symptoms:

              If the laptop is only connected to the AC adapter (battery removed):

              When I press the power button, the keyboard backlight and the display backlight are turning on. Caps key light is lightning, but key does not respond to pressing it.

              The power/battery...
              01-08-2025, 05:45 AM
            • Loading...
            • No more items.
            Working...