PCB Probes

Modern high-density printed circuit boards (PCBs) are difficult to debug using regular oscilloscope probes.  Keeping good contact with a trace, chip leg, or test-point is barely possible.  If you need to measure more than 1 or 2 signals then you quickly run out of hands.

Here is a method for mounting a PCB on a frame of aluminum T-slot extrusions.  A set of 9 clearly labelled pogo-pin probes with 3 different lengths can be moved about on the T-slot frame.  The probes make good contact with the board and won't shift if you move your oscilloscope leads around or bump into the board.

I have been using these probes professionally since March 2021.  This is the third version.  They have increased my productivity and reduced my debugging headaches.  

When you put together the T-slot frame look carefully at the pictures.  You want an open end on each section so you can slide in the T-nut of the probes and move them around.

T-slot that I used is 30x30 6-series:
https://us.misumi-ec.com/vona2/detail/110302686450/?ProductCode=HFS6-3030

 
M4 x 12 mm socket head cap screws are used to mount the post to the T-slot, 
you also need M4 T-nuts that match the profile of your T-slot extrusions.  These are also used on the part that mounts the PCB to the frame.
https://www.grainger.com/product/Socket-Head-Cap-Screw-M4-0-22UC47

For each probe you will need three M3 x 10mm socket head screws and
3 brass heat set inserts size M3.  These are also used on the PCB Mounts (1 each).
https://www.adafruit.com/product/4255

Pogo pins are also from AdaFruit, these are the smallest ones I could find:
https://www.adafruit.com/product/2430

After printing, clean up any rough edges and remove support material.  Then add your brass heat set inserts.  Assemble the Post, Arm1, Arm2, and Arm3.  Use a pin to clear out the slots where your pogo-pins will go and then carefully insert them.  

Use 22 AWG stranded hook-up wire.  Route the wire first, then wrap the end around the pogo pin below Arm3 and solder it in place.  This will prevent the pogo-pin from moving up the slot when its spring is compressed.  Check the pictures to see how the wire is stripped and routed.

OpenSCAD source files are included so you can modify the parts to fit your particular PCB.  The part called “Mount” is most likely to need adjustment since not all PCBs will have holes in the same location.

I print these parts in PetG, use 2 or 3 perimeters, 20% triangular infill, 0.3 mm layers.  Be careful how you orient the parts on the build plate!  Notes on each file show which ones need support.