Tektronix 2225 Oscilloscope control knob

thingiverse

I purchased my Tektronix 50 MHz scope used several years ago. It lacked the control knob for trigger level, which I would often swap with the "holdoff" knob located directly below it. However, one day the prong seating the knob finally snapped off due to fatigue and frequent insertions. Typically, I only use one channel on the scope, so I carefully used the channel 2 position knob in place of the two missing knobs. When I received a 3D printer for Christmas, this knob was the first thing I modeled. I initially created it with a 1mm split in the tip, similar to the original. However, PLA is even more brittle than the factory plastic used in the original knob, so it didn't last long. I modified my model twice - first with a .5mm split, which resulted in stringy prints and likely failure, and again without any split at all. I've been using the scope with the non-split knob for several weeks now, and it's solid and less prone to failure than the original. This knob is intentionally designed as a snug fit into the trimmer, but I don't recommend forcing it too hard, as this may damage your vintage scope. It should only take a few seconds to sand or file the tip if the fit is too tight. This knob can be used in place of either channel's position knob, trace step knob, horizontal coarse and fine positions, trigger level, and holdoff. Since I was missing two knobs, I printed the knob in both yellow and blue. I use the colored knobs for vertical position channel one (yellow) and channel 2 (blue), and marked my probes with the same colors. My original design aimed to duplicate the factory knob as closely as possible, but I dislike the split tip knob due to its durability issues. However, I've included the split knob STL file for those who prefer it. I urge you to use the non-split version instead. I printed these knobs at standard .2 resolution on my CR-10 knock-off printer using the default Cura CR-10 profile with 20% infill. To avoid a friction-causing seam in the center portion of the knob, I configured "Z Seam Alignment" to "random," which worked well for me. I hope this is helpful to others who may be facing similar issues with their vintage scopes.