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Bestec ATX250-12E up and running!

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    #41
    Re: Bestec ATX250-12E up and running!

    Must wear a leisure suit to do so....
    veritas odium parit

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      #42
      Re: Bestec ATX250-12E up and running!

      Originally posted by Toasty
      Must wear a leisure suit to do so....
      Mann-Made Global Warming.
      - We should be more concerned about the Intellectual Climate.
      -
      Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
      - Dr Seuss
      -
      You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
      -

      Comment

        #43
        Re: Bestec ATX250-12E up and running!

        New layout for DM311 add on pc board. Features "McIverish" heat sink cut from tin can using tin cutter. Photos attached showing pc board attached to main heat sink.
        Attached Files
        Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

        Comment

          #44
          Re: Bestec ATX250-12E up and running!

          Nice, clean layout! How hot does the heatsink get? How hot does the DM311 get without the heatsink?

          I'm going to be building my board soon and am thinking of a glue-on MOSFET heatsink for the DM311 in addition to a tin can sink.

          Comment

            #45
            Re: Bestec ATX250-12E up and running!

            On my boards, I have never put a heavy load on the 5vsb, so the DM311 has never been too hot for me to touch. The "tin can" heat sink was just an add on idea for future loading. I might mention ......... don't touch that heat sink while the power supply is running. It has the switching signal on it between the +320 volt source and the FET switcher, an AC signal of something like about 600 volts peak to peak. Notice also that the added heat sink does not touch the other heat sink (which is tied to AC common on this model Bestec).
            Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

            Comment

              #46
              Re: Bestec ATX250-12E up and running!

              On Bestec ATX-250 12E #2 I have completed the recap process. The first 12E had mostly JPCE-TUR capacitors. This one had mainly Jamicons. So here is an analysis of how the Jamicons held up.

              The two mains were CapXon 470 uF/200 volts. I had a burned board with a pair of Panasonic 560 uF/200 volt capacitors so changed the CapXon for the better Panasonic.

              12 volt rail:
              C32A Jamicon 2200 uF/16V esr=.02 -> Samxon 3300 uF/16V esr=.02
              C29 Jamicon 1000 uF/16V .07 -> Samxon 3300 uF/16V .02

              5 volt rail:
              C31 Jamicon 1000 uF/10V .10 -> Nichicon PW 2200 uF/10V .02
              C30 Jamicon 2200 uF/10V 2.3 (bulging) -> Nichicon PW 2200 uF/10V .02

              3.3 volt rail:
              C26 Jamicon 1000 uF/10V .11 -> Nichicon PW 2200 uF/10V .03
              C25 Jamicon 1000 uF/10V .09 -> Nichicon PW 2200 uF/10V .03

              -12 volt rail:
              C32 Jamicon 1000 uF/16V .07 -> Nichicon PW 1000 uF/16V .05

              5vsb rail:
              C37 Jamicon 1000 uF/10V .11 -> Nichicon PW 1000 uF/10V .05
              C36 Jamicon 1000 uF/10V .10 -> Nichicon PW 1000 uF/10V .05

              Remaining capacitors:
              C12 Jamicon 2.2 uF/50V 2.2 -> Nichicon PW 2.2 uF/50V .50
              C13 Jamicon 0.1 uF/63V 23 -> Nichicon VZ 0.1 uF/50V 18
              C24 Jamicon 0.1 uF/63V 20 -> Nichicon VZ 0.1 uF/50V 17
              C39 Jamicon 1 uF/50V 2.7 -> Nichicon PW 1 uF/50V 2.0
              C35 Jamicon 22 uF/50V 1.2 -> Nichicon PW 22 uF/50V .45
              C35A Jamicon 2.2 uF/50V 1.8 -> Nichicon 2.2 uF/50V .53
              C45 Jamicon 10 uF/50V 1.5 -> Nichicon PW 10 uF/50V .51
              C27 Jamicon 1 uF/50V 2.7 -> Nichicon PW 1 uF/50V 2.3
              C33 Jamicon 0.47 uF/50V 7.0 -> Nichicon PW 0.47 uF/50V 3.6
              C46 Jamicon 10 uF/50V 1.8 -> Nichicon PW 10 uF/50V .54
              C59 Jamicon 2.2 uF/50V 2.5 -> Nichicon PW 2.2 uF/50V .52

              The "critical" capacitor:
              C1 Jamicon 10 uF/50V >99 (not bulging) -> not used in DM311 mod
              C50 CapXon 220 uF/25V .92 -> Nichicon PW 220 uF/50V .05

              Note that C50 at 25 volt rating was changed to 50 volt rating. It normally runs at 20-22 volts. If 5vsb goes up, the voltage across C50 goes up proportionatly. Not much room for overload - one of the reasons this model had high failure rate.

              The esr readings of the JPCE-TUR capacitors on the first Bestec were much lower (see earlier post in this thread) than the Jamicon capacitors. The Nichicon PW had nice low readings.

              Before putting it back in the box, here are some photos of this Bestec with mod and recapped.
              Attached Files
              Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

              Comment

                #47
                Re: Bestec ATX250-12E up and running!

                Those samxon's the RS series from topcat?

                Wondering how the ESR is on them. Too lazy to look up data sheets.

                Comment

                  #48
                  Re: Bestec ATX250-12E up and running!

                  Yes
                  Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

                  Comment

                    #49
                    Re: Bestec ATX250-12E up and running!

                    Remaining capacitors:
                    C12 Jamicon 2.2 uF/50V 2.2 -> Nichicon PW 2.2 uF/50V .50
                    C13 Jamicon 0.1 uF/63V 23 -> Nichicon VZ 0.1 uF/50V 18
                    C24 Jamicon 0.1 uF/63V 20 -> Nichicon VZ 0.1 uF/50V 17
                    C39 Jamicon 1 uF/50V 2.7 -> Nichicon PW 1 uF/50V 2.0
                    C35 Jamicon 22 uF/50V 1.2 -> Nichicon PW 22 uF/50V .45
                    C35A Jamicon 2.2 uF/50V 1.8 -> Nichicon 2.2 uF/50V .53
                    C45 Jamicon 10 uF/50V 1.5 -> Nichicon PW 10 uF/50V .51
                    C27 Jamicon 1 uF/50V 2.7 -> Nichicon PW 1 uF/50V 2.3
                    C33 Jamicon 0.47 uF/50V 7.0 -> Nichicon PW 0.47 uF/50V 3.6
                    C46 Jamicon 10 uF/50V 1.8 -> Nichicon PW 10 uF/50V .54
                    C59 Jamicon 2.2 uF/50V 2.5 -> Nichicon PW 2.2 uF/50V .52
                    interesting to see values for those higher voltage/lower uF caps...

                    Comment

                      #50
                      Re: Bestec ATX250-12E up and running!

                      Here it is, back in the box. It has been recapped. It has the DM311 5vsb mod. It has the added fan which runs when the computer is turned off. The fan acts as a load resistance instead of resistor R102 which does nothing but generate heat.
                      Attached Files
                      Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

                      Comment

                        #51
                        Re: Bestec ATX250-12E up and running!

                        Originally posted by everell
                        ...fan acts as a load resistance instead of resistor R102 which does nothing but generate heat.
                        AWWWW! No more frost-free standby...
                        veritas odium parit

                        Comment

                          #52
                          Re: Bestec ATX250-12E up and running!

                          Need that this time of year.

                          How does one go about hooking up said fan?

                          Comment

                            #53
                            Re: Bestec ATX250-12E up and running!

                            The Bestec ATX-250-12E is the only psu I know of that has this circuit feature. When the computer is turned off, a transistor switches power from the pwm chip to a 1000 ohm resistor. It serves only as a heat generating load. So I remove the resistor (R102) and wire a fan in its place.

                            So go find you a Bestec ATX-250 12E and you can do some cool experiments!
                            Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

                            Comment

                              #54
                              Re: Bestec ATX250-12E up and running!

                              >When the computer is turned off, a transistor switches power from the pwm chip to a 1000 ohm resistor. It serves only as a heat generating load.

                              they need that to accelerate demise of +5vstby circuit!
                              hehe...

                              Comment

                                #55
                                Re: Bestec ATX250-12E up and running!

                                I had the same problem with Seventeam ST-300BLV, +5VSB raise to 9V! because of 10uF/50V CapXon KM.
                                after I replaced it, +5VSB is back to normal.
                                Thank you.

                                POM.
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                                Comment

                                  #56
                                  Re: Bestec ATX250-12E up and running!

                                  Originally posted by everell
                                  My project was a bad Bestec power supply with blown 5VSB. I will now attempt to show photos and my hand drawn schematics.
                                  Hi,

                                  I have also a problem with my bestec ATX-250-12Z rev C power supply.
                                  The green component near the C40 (0,10uF/250V X2) is blown. I want to replase it, but does not know what kind of thing it is. The draw on the pc board is a resistor. But the discription is NTH8.

                                  Can someone tell me what this is?

                                  Thanks in advance

                                  Comment

                                    #57
                                    Re: Bestec ATX250-12E up and running!

                                    That's most likely the inrush current limiter (NTC thermistor). I just measured one i scavenged from a psu, and it has about 45 ohms @ 25degC.

                                    You could either get one from another broken psu, or get one from some electronics shop.
                                    Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

                                    Comment

                                      #58
                                      Re: Bestec ATX250-12E up and running!

                                      check the psu first, they wont blow unless something is shorted.

                                      Comment

                                        #59
                                        Re: Bestec ATX250-12E up and running!

                                        The marking on my Bestec ATX-250 12Z is

                                        STK
                                        037

                                        As indicated in above posts, it is a thermistor used as an inrush current limiter. You can probably use one from another power supply, Before replacing, I would check resistance on bridge diodes and switching transistor. A short in either place can cause your problem.
                                        Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

                                        Comment

                                          #60
                                          Re: Bestec ATX250-12E up and running!

                                          Originally posted by stj
                                          check the psu first, they wont blow unless something is shorted.
                                          Not true. I've seen them fail and the PSU is fine after replacement. Especially true if the fuse is good. Most likely they blew because of they were underrated. Someone else had one do the same and posted in here awhile ago... momaka?

                                          Recent similar post: https://www.badcaps.net/forum/showthread.php?t=9020

                                          Links in there for parts and specs.

                                          Toast
                                          veritas odium parit

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