Linkworld LPH6-250W innovations...

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  • goodpsusearch
    Badcaps Legend
    • Oct 2009
    • 2848
    • Greece
    #1

    Linkworld LPH6-250W innovations...

    I have already posted about this power supply here:
    https://www.badcaps.net/forum/showth...250W#post99122

    Its parts are decent and I am quite confident it can do the label ratings.

    But some days ago I opened it to check the caps and I noticed something strange:

    https://www.badcaps.net/forum/attach...1&d=1389923108

    The yellow cables of the ATX 12V connector are not directly connected to the PCB, but there is a large resistor in series with them! That resistor rating is 0.1ohm. Why did they do that???

    But wait. There is more! If you can't find the supervisor IC in the photos, well it's because there isn't one! Does this mean that the psu has no protections at all??? Is it possible that it doesn't even have a short circuit protection?

    Btw is there a chance that they put the resistor as over-current protection for CPU-12V?
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    • c_hegge
      Badcaps Legend
      • Sep 2009
      • 5219
      • Australia
      #2
      Re: Linkworld LPH6-250W innovations...

      With no supervisor IC, the thing wouldn't work. It's in the same place it usually is on half bridge PSUs (although it may use one combo IC, rather than two separate ICs). As for the resistor, I have no idea why that would be there. maybe they were just trying to compensate for bad 12V voltage regulation?
      I love putting bad caps and flat batteries in fire and watching them explode!!

      No wonder it doesn't work! You installed the jumper wires backwards

      Main PC: Core i7 3770K 3.5GHz, Gigabyte GA-Z77M-D3H-MVP, 8GB Kingston HyperX DDR3 1600, 240GB Intel 335 Series SSD, 750GB WD HDD, Sony Optiarc DVD RW, Palit nVidia GTX660 Ti, CoolerMaster N200 Case, Delta DPS-600MB 600W PSU, Hauppauge TV Tuner, Windows 7 Home Premium

      Office PC: HP ProLiant ML150 G3, 2x Xeon E5335 2GHz, 4GB DDR2 RAM, 120GB Intel 530 SSD, 2x 250GB HDD, 2x 450GB 15K SAS HDD in RAID 1, 1x 2TB HDD, nVidia 8400GS, Delta DPS-650BB 650W PSU, Windows 7 Pro

        Comment

        • goodpsusearch
          Badcaps Legend
          • Oct 2009
          • 2848
          • Greece
          #3
          Re: Linkworld LPH6-250W innovations...

          There is KA7500B. Usually there is also LM339 or WT7510 or other but there is none here.

            Comment

            • Pentium4
              CapXon Be Gone
              • Sep 2011
              • 3741
              • USA
              #4
              Re: Linkworld LPH6-250W innovations...

              A Linkworld with a varistor, input filtering, bridge rectifier, and good sized PI filter on the 12V? That's a rare species right there! I guess Linkworld was better back in 2001. And all the CS caps look "fine" I wonder if they're still in spec. I'd go as far to say that they're even better than Fuckyou's

              As for the resistor, I have no idea! I have never seen that before.

              It's not uncommon to see old half bridge units with just one IC for the entire unit.

                Comment

                • TELVM
                  Badcaps Veteran
                  • Oct 2012
                  • 547
                  • Spain
                  #5
                  Re: Linkworld LPH6-250W innovations...

                  Also one of the secondary PI coils seems to lack its core .

                    Comment

                    • goodpsusearch
                      Badcaps Legend
                      • Oct 2009
                      • 2848
                      • Greece
                      #6
                      Re: Linkworld LPH6-250W innovations...

                      Originally posted by TELVM
                      Also one of the secondary PI coils seems to lack its core .
                      This is not rare:
                      https://www.badcaps.net/forum/showth...8282#post98282

                        Comment

                        • lti
                          Badcaps Legend
                          • May 2011
                          • 2545
                          • United States
                          #7
                          Re: Linkworld LPH6-250W innovations...

                          Maybe they wanted to limit the current so the CPU won't draw too much power from their crappy PSU.

                          It could work without the supervisor chip. They can always fake all the signals it produces so it stays running until something goes . Just connect the gray wire to +5V and make sure the controller is always running.

                            Comment

                            • goodpsusearch
                              Badcaps Legend
                              • Oct 2009
                              • 2848
                              • Greece
                              #8
                              Re: Linkworld LPH6-250W innovations...

                              Wonderful! I removed the resistor and reoiled the fan...

                                Comment

                                • momaka
                                  master hoarder
                                  • May 2008
                                  • 12164
                                  • Bulgaria
                                  #9
                                  Re: Linkworld LPH6-250W innovations...

                                  Originally posted by goodpsusearch
                                  The yellow cables of the ATX 12V connector are not directly connected to the PCB, but there is a large resistor in series with them! That resistor rating is 0.1ohm. Why did they do that???
                                  I can only think of two reasons:

                                  1) Limit the current that can be drawn by the 12V rail - most probably meant for large transient currents that may trip the under-voltage protection (if there is even one) or short circuit protection. If that's the case, this screams CRAPPY FEEDBACK LOOP DESIGN!

                                  2) Reduce ripple going to the motherboard. The resistor and the CPU VRM high-side capacitors on the motherboard form an RC low-pass filter, thus greatly reducing any ripple that may be coming from the PSU. This allows the PSU to be more "sloppy" with the ripple output.

                                  Funny how they gave the 12V rail a rating of 10A. At 10A, this 0.1 Ohm resistor would have dissipated R*I^2 = 0.1 * 10^2 = 10 Watts! Even at 5A, that's still 2.5 Watts. NOT GOOD!

                                  Originally posted by goodpsusearch
                                  But wait. There is more! If you can't find the supervisor IC in the photos, well it's because there isn't one! Does this mean that the psu has no protections at all??? Is it possible that it doesn't even have a short circuit protection?
                                  I doubt there are no protections. Even the most cheap and dirty PSUs have short circuit protection. OVP and UVP.... maybe.
                                  The protection(s) are probably implemented in a discrete manner with TO-92 transistors. Not unusual on old half-bridge designs that have only a 494 or 7500 secondary-side PWM controller and nothing else.
                                  Last edited by momaka; 01-20-2014, 02:19 AM.

                                    Comment

                                    • goodpsusearch
                                      Badcaps Legend
                                      • Oct 2009
                                      • 2848
                                      • Greece
                                      #10
                                      Re: Linkworld LPH6-250W innovations...

                                      You are right. That resistor got really hot during operation! The glue they used that made the resistor contact with nearby capacitors didn't help either!

                                      When measuring 12V from molex connectors or 20pin mb connector I got 12.5-12.8V. At the same time the ATX12V connector gave me 11.2-11.4V. This is really bad.

                                        Comment

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