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Electronics => Repair => Topic started by: Blynski on March 17, 2023, 07:24:16 pm

Title: Fluke 52 II PCB missing passive component
Post by: Blynski on March 17, 2023, 07:24:16 pm

I am trying to fix my dad's Fluke 52 II and it appears to have multiple issues.  Firstly, half of the header contacts had broken solder joins which I repaired.  Secondly, it appears to have some damage and a missing passive component (probably a capacitor based on how it is acting).  Attached is a picture I found of a good board with the missing component circled.  Does anyone know the correct value of this component so I can order one and replace it (or someone with a schematic)?

Title: Re: Fluke 52 II PCB missing passive component
Post by: fzabkar on March 17, 2023, 07:59:34 pm

The colour is reminiscent of a precision resistor. What resistance do you measure for the "2742" part and for the other unmarked part?

Title: Re: Fluke 52 II PCB missing passive component
Post by: Blynski on March 18, 2023, 02:42:14 am

Thanks for the hint on it being a resistor. I’ll take some measurements tomorrow and report back.
Assuming you are correct I would still need someone with a good board or a schematic to help me out on the needed value.

Title: Re: Fluke 52 II PCB missing passive component
Post by: fzabkar on March 18, 2023, 03:10:57 am

The Linear part is a dual precision reference:

https://www.analog.com/media/en/technical-documentation/data-sheets/1034fe.pdf (https://www.analog.com/media/en/technical-documentation/data-sheets/1034fe.pdf)

That would lend support to the precision resistor idea.

Title: Re: Fluke 52 II PCB missing passive component
Post by: Blynski on March 19, 2023, 01:34:43 am

Based on taking measurements on my board, I would agree that they are in fact resistors.  Picture attached of the measured values.  Essentially two  27.4k ohm and one 5k ohm resistor.  So at least I know I'm looking for a precision resistor, but still need the correct value...

Title: Re: Fluke 52 II PCB missing passive component
Post by: fzabkar on March 19, 2023, 05:37:58 am

Just in case you don't have it, here is the service manual (but no circuits):

https://elektrotanya.com/fluke_51_52_53_54_series_ii_thermometer.pdf/download.html#dl (https://elektrotanya.com/fluke_51_52_53_54_series_ii_thermometer.pdf/download.html#dl)

Your board is the "isothermal PCA". I suspect it provides cold junction compensation for the thermocouple.

Title: Re: Fluke 52 II PCB missing passive component
Post by: coppercone2 on October 04, 2024, 06:36:50 am

Ah I fixed mine after dropping it, I was very confused.


YOu see, that board has pins on it that are SMD! I thought they were through hole and figured there is no way that could break.