I'm a huge fan of Sencore equipment for the most part, but their transistor testers are getting pretty long in the tooth and some now require service. Additionally, the pushbuttons on the TF26 are multi-gang switches that aren't easy to get to for cleaning and lubrication. The unit I received worked on NPN transistors, but no response when testing PNP's even after routine preventive maintenance. Since I already have a working TF40 (Pocket Cricket) and a huge workload of customer jobs, I decided to just toss it and maybe take my chances with another one if having a spare continues to be important to me.
Note that my rating is based on the equipment's current condition, not its original quality out of the factory. Sencore is great gear, but all electronic stuff has a limited realistic lifespan and potential buyers should take this into consideration. I wasted less than $50 so it's no big deal, and I got what I paid for.
This is the easiest way to test a transistor. You don't have to know basing or type or if it's an NPN or a PNP. If you have an electronic background this unit is easy to trouble shoot repair and calibrate. Not all of the parts but many of the parts are still available on the internet.