A rolling test stand is a really nice tool to have. I have had one made by KFC-Zeller in Germany for years but I was not using mine because it was not installed permanently.
I modified it to permanently install it on my workbench ready to use
The STL files for the blocks are available on my GitHub if you want to make one for yourself. All that you need is some 3mm and 6mm linear rods. The trolleys can be found on AliExpress. (search for: Track Roller Test Stand)
During winter time I like to fool around with model trains. Because of the Covid-19 evening curfew, the winter season is extended and I took the time at home to really get into converting some of my locomotives to LED lights and ESU Lokpilot decoders.
The Märklin BR 128 was the first patient and received a new 21MTC adapter PCB. Stock from Märklin it already has LED lights but I wanted to add High Beam and Shunting lights so it also received new LED PCBs.
The PCBs were designed in Eagle CAD and made by JLCPCB in China. They use all SMD components so I opted for using solder paste and a hot air solder station to do the soldering. The design also incorporates two parallel capacitors that function as a power buffer. They can be switched on or off using an SMD switch on the adapter PCB.
To prevent light scatter I used Fusion 360 and my Prusa MK3s to make a plastic spacer that goes in front of the LED PCBs.
I’m very happy with the end result and clean install. The design files are available on my GitHub.