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Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

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    #76
    Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

    Maybe replace the cm6800 with a new or equivalent.

    Comment


      #77
      Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

      I already did that

      And i think that the standby chip is good, because i removed it, and the other other one from the other zalman, and they both tested good as far as i could see.
      All pins measured the same resistance to ground pin, and no shorted internal diodes
      I also checked the empty PCB holes to floating ground and they all roughly tested the same.
      Then i put them back on the boards, swapping them over.
      The only noticeable change was that the fan, instead of spinning for a second or two just twitches now (one blade turn at most).
      So i'll swap them back over again

      i'll remove the supervisor chips, test them, and swap them over.

      In fact, i might see what the standby does with the supervisor chip removed.
      Last edited by socketa; 07-09-2023, 07:17 PM.

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        #78
        Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

        Leave the supervisor in place and ground out the FPO pin to secondary gnd. That disables it.

        Comment


          #79
          Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

          i was too quick, and swapped them over, but it didn't make any difference;
          so i put them back as they were originally, and now the PSU doesn't even try to start when PSON is grounded (no voltages come up at all), even though the supervisor has 4.4V VCC.
          And the 5V still disappears when i connect it to the headlight bulb, and pulses up to nearly 1V every few seconds
          Looking at the typical application circuit, i checked Rocp resistor, which is good
          The diode, resistor, and capacitor (SMD, as opposed to an electrolytic cap as the application circuit says), that are attached to VCC pin, are all good
          And the capacitor that is across the feedback diode is measuring 1nf in circuit
          So that section all looks good. Right?
          Last edited by socketa; 07-09-2023, 11:59 PM.

          Comment


            #80
            Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

            That’s one of the reasons why I said ground temporarily the FPO pin out, that disables any protection from the supervisor and the primary can’t turn off because of under voltage, over voltage, etc condition.
            Problem now is that nothing works and why? Could be anything from a forgotten solder or bad solder joint, to an overheated or somehow damaged component, broken trace, etc.

            Next problem is / was, that the FPO pin on the supervisor was low on some testing, then it was measured high again on other testing. Another reason to disable it because all this adds to confusion. Once this situation is set there is no variable, no matter what. You just couldn’t go Willy Nilly anymore and have to remember no to overload, put the power supply on a dim bulb tester.
            Last edited by CapLeaker; 07-10-2023, 04:50 AM.

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              #81
              Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

              "Nothing works" - um, no - the 5vsb sill comes up
              And there is no lifted traces, and no bad solder joints
              And i used a dim bulb tester before connecting directly to mains
              The 5vsb was obviously getting worse over time. It now fails even if i connect a bulb that would draw less than 0.1A
              Last edited by socketa; 07-10-2023, 02:33 PM.

              Comment


                #82
                Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                Just noticed that i mistakenly replaced the Rocp resistor with the one that i was using to discharge the primary caps (they both looked the same)
                The twitching fan came back, but now the 12v doesn't come up at all
                i think that the chip is probably bad
                And found out that the chip from the other PSU is probably faulty; as the resistance from from pin 1 to ground pin is in the Mohm range, compared to 50ohm in this one, despite all of the internal diode measurements being the same
                i ordered some more chips (hopefully, not fake ones)
                Last edited by socketa; 07-10-2023, 06:15 PM.

                Comment


                  #83
                  Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                  Originally posted by socketa View Post
                  Just noticed that i mistakenly replaced the Rocp resistor with the one that i was using to discharge the primary caps (they both looked the same)
                  The twitching fan came back, but now the 12v doesn't come up at all
                  i think that the chip is probably bad
                  And found out that the chip from the other PSU is probably faulty; as the resistance from from pin 1 to ground pin is in the Mohm range, compared to 50ohm in this one, despite all of the internal diode measurements being the same
                  i ordered some more chips (hopefully, not fake ones)
                  That's what I figured along the line did happen. What chip are you talking about now the supervisor, the CM6800 or the STR-A6000? The STR-A6000 is always on and does make your STBY voltage. From there it goes to the supervisor and then back to the CM6800 (FAN4800) to turn the PSU fully on.

                  I had the impression that the other PSU you were using was actually working? Maybe I have a wrong assumption?

                  Now no 12V rail? How much voltage you got in the main filter cap? Check the big diodes on the 12V rail. Maybe one is shorted?

                  Comment


                    #84
                    Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                    Was still talking about the standby chip
                    And yes, the other PSU is faulty - only 2.5V on standby
                    Swapping the chips didn't make any difference to that
                    Back to the original PSU...
                    320V across main filter cap, and there is two through-hole diodes (one's connected to DC+, and the other one's connected to DC-) that both test good on diode mode.
                    I connected a 12V 23W bulb (that draws less than 0.1A when powered by 5V) to the standby rail, and it lit up; and noticed that the standby voltage dropped to 4.4V
                    Then i tried it a few minutes later and the voltage now only drops by 0.02V
                    The voltage goes back up when the bulb is removed
                    So i tried the headlight bulb again, and the voltage drops to zero, and it does it's voltage pulsing thing (briefly up to 1V, and back down for the rest of the cycle) every couple of seconds.

                    Thinking that 50ohms between pins 1 and 3 looked suspicious, i swapped the chips over and now the headlight bulb glows and the voltage remains at 5V.
                    So now the standby appears to be good, although i haven't let it power the bulb for an hour
                    The original chip is now definitely faulty (remembering, that it was working OK earlier on) - it looks something happened between post #65 and #67 that damaged it.

                    i'm weary of trying to power up the PSU now, in case it blows up the chip again
                    although the resistance of both secondary sides of the PSU's standby outputs are the same
                    Last edited by socketa; 07-11-2023, 02:21 AM.

                    Comment


                      #85
                      Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                      All of the secondary outputs give the same measurement on diode mode, and resistance mode, with no shorts
                      But i'm still concerned that the chip might get damaged if i try to start the PSU up, because of that burning smell that happened before.

                      Comment


                        #86
                        Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                        Depending on which STR-A6000 series PWM, I am guessing STR-A6059 or STR-A6069 they only do like 11W on 120V and 17W on 230V. That’s not a lot. So don’t be obsessed by loading that STBY to the hills as it isn’t made for providing large continuous current, plus it has to handle the load connected to it already on top of the light bulb. If you wanna make reliable repeatable current measurements, you need a electronic load, not a light bulb. The light bulb is just a confirmation that the PSU can handle ‘a’ load. Cold bulbs draw more than warm bulbs etc.

                        If all the other voltage rails are up but no 12v, the power supply should start and immediately shut down due to the supervisor FPO pin going high. Don’t get the idea to disable the supervisor right now, figure out first why there is no 12V. Either the rectifier diodes are shorted, or something is a miss with the mosfet / gate driver on the primary.

                        Comment


                          #87
                          Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                          None of the main rails come up when i ground PSON
                          All that happens is that the FPO pin, that's on the PS229 chip, goes from 4.4V to 61mV - which, according to the datasheet, indicates that it's not seeing any problem. (probably because the main PSU isn't even working yet)
                          FPO is connected to the middle optocoupler, and the primary side of that optocoupler has a voltage drop across it that goes from 9v to 127mV when i ground PSON, which is good
                          So, yeah, that means that there must a problem somewhere in the PWM driver circuitry
                          Last edited by socketa; 07-11-2023, 04:53 PM.

                          Comment


                            #88
                            Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                            Poke around the CM6800 maybe VCC is missing, thus playing dead? Or this IC is bad.

                            Comment


                              #89
                              Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                              VCC, pin 13 - 14V comes up when i ground PSON
                              PWM voltage feedback input, pin 6 - 4V comes up when i ground PSON (has now dropped to 3.4V after rechecking a few times)
                              PWM driver output, pin 11 - 6.9V when i ground PSON (top side of PCB sometimes made a buzzing noise when applying the probe)
                              Previously, I did swap the chip over with a new one that was working with the fan spinning for a bit
                              Should i swap it back and see what happens?
                              It's from China, so maybe it went faulty since then
                              The two main MOSFETS test good.
                              The APFC part has being bypassed quite some time ago, and i don't think that it's essential for the PSU to run; as i've bypassed it in the exact same chip, that's in another PSU, and it runs fine.
                              Last edited by socketa; 07-11-2023, 10:45 PM.

                              Comment


                                #90
                                Re: Zalman ZM500-GV stops after 40s and 5VSB drops to 2.5V

                                Well, now the standby won't light up the headlight bulb anymore
                                The voltage goes to zero and pulses like before
                                i thought that something might go wrong when i heard that buzzing sound
                                i removed the chip and checked it, it seems OK (it hasn't failed like the other one), but who knows?
                                Last edited by socketa; 07-11-2023, 11:51 PM.

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