WaveyDipole, the rotary switch test on the Agilent/Keysight meter was indeed quite worrying. However, there are a few variables that were discussed at the time that could sway the decision towards either way.
- The somewhat premature break of the Keysight was quite worrisome, but unfortunately the sample size of "one" turns this test somewhat inconclusive.
- The material used in the switch is the most troublesome - perhaps the U123x is built down to a price? I really don't think so, but unfortunately I sold my U1233A a long time ago - otherwise I would have compared it with the U1273A and the U1282A.
- The continuous rotation through the entire scale could potentially cause premature wear due to increased temperature. Joe told us he made sure the twists and turns were quite gentle and not aggressive nor too quick.
- One additional not tested scenario that could cause even extra wear on the U123x line is that it can also be turned with the thumb - this exerts horizontal forces that may wear the opposite side of the tracks faster. For that Joe would need to assemble an quite different test jig and would mean nothing for the other DMM models.
Overall, the sheer number of cycles is daunting for a regular user - after all, 50.000 switches in the lifetime of such equipment means that someone that turns it over 10 times a day without weekends would make it last for about 14 years.
Incidentally I came across a used U1273 for a reasonable price. There were a couple of minor scratches on the display, but otherwise it looked clean. However, it was from overseas (far east) and comes only with basic DIY looking probes, so the purchase looks a bit risky although he claims to be a second-hand goods seller.
Specifically for the U1273A, on the price I would add the possibility of requiring a new display. Keysight sells a
replacement display at a very steep price but others folks around here couldn't find quite a drop-in replacement. Among the various reports here on EEVBlog, the vast majority of issues were observed in the previous generation unit U1253, but some reported issues on the U1273A. Mine is going strong for a few years used many times during the week, but it is a spoiled unit that is stored and operates exclusively on non-extreme temperature and humidity.