Electronics > Projects, Designs, and Technical Stuff

Yet another resistance decade box

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JacquesBBB:
On One of the external holes, there is a pin that has been melted to hold firmly the board. Just cut the top part as close to the board you can ( i do it with a sharp wire side cutter).

Then press on the other side starting with the side with no pins. It should come now easily.

Do not break the pins. They will be useful to hold firmly the new board.

To put the new boards you need to be sure they are completely engaged on the pins. This needs some local pressure, they will snap nicely.

mrjoda:
check this. It is easy

https://youtu.be/6eoKMs7ws6U

nikifena:
Finally I finished my decade box.
The enclosure is made from 1mm sheet metal.

Alex Nikitin:

--- Quote from: nikifena on September 21, 2016, 07:03:25 am ---Finally I finished my decade box.
The enclosure is made from 1mm sheet metal.

--- End quote ---

Looks good! However, a couple of suggestions:

1) Connecting a metal box to one of the terminals might not be a good idea if you plan to use the box as a resistor substitute in a live circuit. IMHO either the box should be plastic with an internal shield or a metal with a separate connection to the case (this also would provide a nice reduction in the stray capacitance across the resistors stack if the box is grounded separately).

2) You've connected the case to the high resistance end of the stack. This way the parasitic capacitance and leakage across the high value resistance is maximized. It makes more sense to connect the case/screen to the lower resistance side if you don't have a separate connection for the case.

Cheers

Alex

nikifena:
Thanks for your suggestions Alex.
I will use for testing multimeters or if I need a variable resistor in some situations. The highest resistance values are to check the maximum measured capabilities of the DMM.

Yes, you are absolutely right! Grounding the isn't the best idea which I made ;) Unfortunately there is not enough space for a switch. I will leave the existing box as is, but I will keep in mind about your recommendations in the future :)

Thanks again ;)

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