Repair of Tektronix P6231 Z0 probe tip

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I got a Tektronix P6231 variable offset Z0 probe.  It had no tip.  This is how I repaired it.  The procedure should work for other 2.5 mm subminiture Z0 probes such as the P6156.

The part number for the tip is 206-0279-00 or 206-0279-10.  I failed to acquire one.

I found an SMA connector for RG-174 cables.  I cut a #5-44 thread on the part for crimping the shielding.  I had to grind the face of the die so the thread could go close enough to the connector body.  My connector was big enough.  This part on some connectors may be too small.  I replaced the stranded center conductor in a piece of RG-174 cable with a piece of solid 24 AWG wire.  I bent it slightly so it made good contact with the hole in the probe.  This way I converted the connector for the probe tip to SMA.

I got an edge-launch SMA connector.  I put in a piece of FR-4 without copper clad to make soldering easier and also to make the pin more rigid when glued.  I shortened the center pin.  I connected a 0402 size 402 Ω resistor and a pin to it.  I applied epoxy.  I added a pogo pin for the ground connection.

It had enough bandwidth for my 1 GHz oscilloscope.  I got no overshoot when measuring a square wave with edges faster than the oscilloscope can measure.







For other ways of making Z0 probes with an SMA port, one may also want to look at the stuff named akl-pt from this link (not mine).  https://github.com/azonenberg/starshipraider  There is a video reviewing it.