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Fluke 87 Meter repair

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    Fluke 87 Meter repair

    I have a model 87 fluke multimeter with Q8 showing bad and I am looking to replace it. Fluke no longer stock it and don't have a substitute for it I can't see any markings on it so can't find a data sheet. Was wondering if someone could recommend a substitute from the schematic attached
    Attached Files

    #2
    Re: Fluke 87 Meter repair

    The number shown in the parts list for the MFRS is SSTVNS009-T1 but this # do not show any results. The description given in the parts list: Transistor, SI, N-DMOS FET, SOT23.
    Attached Files

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      #3
      Re: Fluke 87 Meter repair

      Absolute murder to find the part! Q8 N-ch small signal DMOS FET for battery switch.
      TEMIC/Silconix SSTVNS009-T1 SOT-23, Fluke 830851 replaced by Fluke 927538. Not in Silconix 1986 FET databook.

      The part is now 2N7002, easy to find. BSS138 would likely work too.
      Last edited by redwire; 08-05-2020, 12:42 PM.

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        #4
        Re: Fluke 87 Meter repair

        Thanks redwire that will get me up and running appreciate the help

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          #5
          Re: Fluke 87 Meter repair

          What happened to the meter that caused Q8 to go bad?
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            #6
            Re: Fluke 87 Meter repair

            Originally posted by retiredcaps View Post
            What happened to the meter that caused Q8 to go bad?
            Not sure I think I may have put a prop across it with the unite powered on I smoked Q8 and Q10 in the process. I picked up the meter because it had an issue with a high amperage spike and I didn't help none. One of these monuments.
            Last edited by davg; 08-05-2020, 06:26 PM.

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              #7
              Re: Fluke 87 Meter repair

              I was wondering about this too, normally it'd take quite a bit to fry Q8 and normally if Q8 goes, the whole meter is likely not salvageable...
              But if you zapped it externally directly with some other issue, then this may not apply.

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                #8
                Re: Fluke 87 Meter repair

                I'm in the process of collecting the various components needed hopefully I didn't do to much damage and can revive it???

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                  #9
                  Re: Fluke 87 Meter repair

                  Q8, Q10 are at the power system for the DMM IC, which is never supposed to see any overloads. It could happen if you were running the DMM from a bench power supply instead of the 9V battery and caused a ground fault. But this is uncommon.
                  I would say good chance the DMM IC is fried if those parts failed There's a bunch of parts to protect the DMM IC and why didn't they work?

                  You could leave out Q8, Q10, Q3 and jumper battery(-) to VSS at C21 just to see if the meter can boot up. If there is a short or overcurrent on the VDD/VSS I think the DMM IC has shorted.

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