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Repair of 5160 XT power supply

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    Repair of 5160 XT power supply

    Hello,

    I have two IBM 5160 from 1985 and 1986 with the 220V "Schrack" 130W supply.
    Both have now output at all voltage-lines. I have testes under load condition with a mainboard, cga, floppy-adapter, two fullsize-floppies.
    If I switch the supply on, at my postcard only the 12V-voltage-LED lights shortly.
    The fans are turning (220V). The fuses are OK. I measured most diodes - they seems to were OK.
    In the supplys are no damages visible.

    Have someone a hint for a typical failure?
    Means the non lighting +5V-LED, that there is the error?
    Has anybody a schematic for this supply? - In the technical reference of the XT is it not!

    thanks and greets
    Christian

    #2
    Welcome to these forums.

    A common problem with the IBM 5160 is that a tantalum capacitor on the motherboard goes short circuit and overloads the power supply. You can see how common that is by looking at a list of 51xx motherboard failures at [here].

    A procedure for working out which capacitor is faulty is at [here]. Have you tried that?

    Comment


      #3
      Hi, at one mainboard the C56 had a short circuit and at the other board was a faulty dram-chip.
      I changed these - and now both boards are running great with an working power supply.
      But both original power supplys are not working...

      Comment


        #4
        +1 on Modem7's site, Follow the minimum diagnostics procedure and report back.

        Comment


          #5
          Thanks for support, but I tested with this minimum configuration.
          Both mainboards are ok, have no short circuits and works with an other IBM supply from 1984 (made in USA).
          The faulty supplys from Schrack (mde in Europe) have both no voltage on all lines. Only the 220V-fan is turning.
          The supplys are defenitie faulty, but where can I start to search... are there typical errors?
          Last edited by vossi; August 12, 2015, 03:03 AM.

          Comment


            #6
            With the PSU powered up and with nothing connected do you still get 0v on all output lines using a DMM to measure the output voltages ?, Could be Cap failure or a short, these old psu's ain't getting any younger, What tools do you have for troubleshooting. Be extremely careful when working on / inside psu's.

            Comment


              #7
              I measured the outputs with a dmm under load with the working mainboard. I think I have to check all the caps first...

              Comment


                #8
                Yes Caps are a likely culprit, Also check the X2 Caps, If they are of the RIFA type replace them while you have the PSU apart.

                Just an aside, Of the 220v Schrack psu's i have, They all power up and output with no load attached due to the load resistors inside albeit not quite optimal, Though i would expect to see in the region of +11 > -11 > +5 > -5 > V with no extra load attached, If the voltages disappear when connecting a known good load it's more than likely cap failure but of course 1 or more Caps could be totally dead hence your 0V output or a short somewhere. Obviously not all psu's are the same.

                Comment


                  #9
                  Today I repaired both 5160 supplys
                  In both the 3300uF caps at the 7905 regulator had short cirtcuits!
                  It's the only cap in the Schrack PSU from this manufactorer - I think it's a bad cap!

                  greets
                  Christian

                  Comment


                    #10
                    In the US 5160 supply from '84 are the RIFA time-bombs. They looked not so good - had some cracks. I changed them with new x2-caps.

                    Comment


                      #11
                      Hi,

                      I am restoring an IBM 5160. The power supply was a bit rusty.

                      The problem:

                      I think the +12 volts is short circuited with the ground. When I measure it with multi-meter for connection (12 volts and one ground) it beeps continuously. And values are similar to when connecting two grounds.

                      That is not normal, right? I should not expect when I power it up that this problem will disappear?

                      Comment


                        #12
                        Originally posted by tonata View Post
                        I think the +12 volts is short circuited with the ground. When I measure it with multi-meter for connection (12 volts and one ground) it beeps continuously.
                        The fact that your multimeter is beeping, suggests to me that you have your multimeter in the 'continuity' setting. For future reference, note that the continuity setting can sometimes be misleading. See the comment at [here].

                        In the case of the IBM 5160, the resistance on the +12V line should not be low enough to trigger your multimeter's continuity beep, and so it sounds like there is a problem there.

                        The problem cause could be on the motherboard, or on an expansion card.

                        Try the procedure at [here]. If the cause is on the motherboard, then I am expecting that the procedure will have you remove/replace motherboard capacitor C56.

                        Comment


                          #13
                          Thank you for your response. Yes, 'continuity'.

                          I am afraid the power supply will damage the motherboard if it not functioning correctly. What are the chances of this happening? I still have not connected the two.

                          Question 1: Probably a capacitor is responsible for the +12 volts lack of resistance? How should I debug it?

                          I have also acquired a HEDEN PSX A968 350 Watt power supply with 20 pins and one 6 pin P8/P9 type of connector. It has the 5,12,-12 and -5 volts. I still need to re-wire it to the IBM 5160 specification. I have the P8 and P9 connectors also.

                          The HEDEN is +5V@25.0A, +12V@15.0A, -5V@0.6A, -12V@0.6A which seems compatible with IBM 5160 power ratings.

                          And PWR_OK (grey) on the HEDEN = Power Good on the IBM 5160. The green PS_OK (HEDEN) would not be used.

                          Questions 2: Would this HEDEN PSX A968 power supply be really compatible?

                          Comment


                            #14
                            Originally posted by tonata View Post
                            I am afraid the power supply will damage the motherboard if it not functioning correctly. What are the chances of this happening? I still have not connected the two.
                            Damage could result through over-voltage. For example, the power supply generating +6V on the +5V line.

                            I expect that a decent power supply will contain circuitry to detect an over-voltage situation, and if detected, shut the power supply down.
                            Some 'cheap' power supplies may not have circuitry to detect an over-voltage situation.

                            Originally posted by tonata View Post
                            Question 1: Probably a capacitor is responsible for the +12 volts lack of resistance? How should I debug it?
                            Use the procedure at [here].

                            Originally posted by tonata View Post
                            I have also acquired a HEDEN PSX A968 350 Watt power supply with 20 pins and one 6 pin P8/P9 type of connector. It has the 5,12,-12 and -5 volts. I still need to re-wire it to the IBM 5160 specification. I have the P8 and P9 connectors also.
                            The HEDEN is +5V@25.0A, +12V@15.0A, -5V@0.6A, -12V@0.6A which seems compatible with IBM 5160 power ratings.
                            And PWR_OK (grey) on the HEDEN = Power Good on the IBM 5160. The green PS_OK (HEDEN) would not be used.
                            Questions 2: Would this HEDEN PSX A968 power supply be really compatible?
                            You have established that the HEDEN generates all of the required voltages, and can do so at greater power than the IBM XT power supply. You have also established that the HEDEN generates a signal that is the same as the POWER GOOD signal generated by the IBM XT power supply. So, it sounds like the HEDEN will work.

                            (By the way. If the HEDEN did not generate an equivalent to the POWER GOOD signal, there are ways around that. An example at [here].)

                            Comment


                              #15
                              Originally posted by tonata View Post
                              ....I still have not connected the two........
                              I'm a bit confused here, When you took those readings, did you take them from the Motherboard +12v - GND connector with nothing connected to the Motherboard ?, Or did you have the PSU on the bench and took those readings from the power connector of the PSU with nothing connected to the PSU ?.

                              What make of PSU is it, 240v 130W Schrack or ??, Have you powered this PSU up on the bench and checked the DC output voltages with nothing connected to the PSU or with a load connected ?.

                              Comment

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