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Siemens D1052 oscilloscope (Gould DSO 4096) repair

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    Siemens D1052 oscilloscope (Gould DSO 4096) repair

    Hi to the best forum on electronics I know of...

    I need help on final step in repairing+restoring oscilloscope mentioned in the title
    (for which i think that nobody can find service manual)
    From start to finish I have done:
    cleaned a 2.4v NICD battery leakage across board with Hydrochloric acid, baking soda for neutralization, and finished with ethyl alcohol. Board does look like new now. Washed with water in between steps.
    Replaced what I have thought all Rifa capacitors with x and y class pp.
    Replaced output capacitors 2x1000uf35v + (1x470uF 25v - this one was manufactured with around double the capacity so I have replaced it with 1000uf one).
    Replaced both buk455-200a with equivalents *one was shorting out because of leaking capacitors
    Replaced BIOS battery with NIMH one.
    Replaced psu fuse.
    Had changed one small resistor as it seemed like it was acting up 0.5w 270k.
    Replaced 3 more capacitors in psu.
    Big blue Philips caps are left in psu as the esr meter showed good values on them.
    Magic smoke came again with Rifa capacitors inside mains ac filter plug.
    Bought a new Arcotronics filter. Feather light but expensive where I live, still wondering what quality is inside...

    Now comes the "good" stuff...

    PSU should give 3 main voltages +5v +16v -5v
    I measured voltages when unit is under normal load and there is a diference in outputs, +16.7v , +5.3v and -4.7v...Now that was strange for me so I checked for resistance between -5v and 0v on unit, and I think that I have found a problem IT IS 10.7 ohms.
    To me that looks like a short somewhere in the unit so I removed one by one plug in cards.
    One when removed raised resistance by huge amount so i found on her what I think is shorted -5v rail to ground or should I say 0v with 10.7 ohms.

    Well now mine question is this,

    1.May I apply higher current on this slot card than 1A with nominal positive voltage with my regulated power supply (which does not have negative output) may I detect some heat on shorted component with my thermal camera or I should not do that until I acquire negative output power supply.

    2. what are mine options with finishing this unit except to through it in garbage.
    Attached Files
    Last edited by Tamo Neko; 12-10-2020, 01:35 PM.

    #2
    Re: Siemens D1052 oscilloscope (Gould DSO 4096) repair

    10.7Ω at -5v = 0.47A load, that seems normal to me for a board like that.
    You did not explain what the problem with the unit is?
    "The one who says it cannot be done should never interrupt the one who is doing it."

    Comment


      #3
      Re: Siemens D1052 oscilloscope (Gould DSO 4096) repair

      Only voltage differences seems out, which I have to guess with the lack of schematics with nominal voltage tolerances. Other lookalike boards on this particular unit have 10 times higher resistance.

      Voltages imprinted on boards are not the same as measured...
      I have no idea of nominal psu voltages on theese 90s scopes.

      And Unit menages to auto calibrate itself this way.Seems to work. This is my first oscilloscope I acquired for learning how to work with them in general.
      Last edited by Tamo Neko; 12-10-2020, 03:30 PM.

      Comment


        #4
        Re: Siemens D1052 oscilloscope (Gould DSO 4096) repair

        Originally posted by Tamo Neko View Post
        Feather light but expensive where I live, still wondering what quality is inside...
        Reminds me of overpriced LED light bulbs in some hardware stores, LOL.

        Pick some of them up, and it feels like zero heatsinking!
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          #5
          Re: Siemens D1052 oscilloscope (Gould DSO 4096) repair

          I will post updates in a few days, as the shops for electronic components are not working because of covid situation....
          I have made a list to buy and replace all electrostatics on these plugin boards.

          Comment


            #6
            Re: Siemens D1052 oscilloscope (Gould DSO 4096) repair

            Per Hanson is quite right. That board is working fine...Thanks Per Hanson for reply...
            I have just finished replacing many axial capacitors that had high vloss just in case.
            The unit manages to calibrate itself fine but I do have one major concern.

            -5v line is still low.*so i have to adjust main pot line for -5v to reach its nominal values...
            That gives me 18 volts on 16v line
            Now I did measure transistor Q1 even after replacment on psu, having a hard time, overheating up to 100 degrees Celsius with no load and 70 degrees Celsius with all loads attached.
            It was on "Q1" bf393 which is now replaced with mpsa42.
            Now Gould 4072-4074 psu units have if not the same circuits.

            So please can someone who has the 4070s manual tell me what does it say about this Q1 NPN transistor. Guideline for what to look for would be also very appreciated.
            Attached Files

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