Modern valve testers

[ppppenguin]

I totally get the point about protecting your PC but what would have to fail on the uTester to put lots of volts down the interface? Even if the 0V rail of the uTester is earthed and the PC is earthed then it would need some pretty dramatic failure in the uTester which would also fry the uTester before it got to the PC. A couple of Transzorbs on the RS232 lines should deal with that.

Thinking about it, it might well be safer to deliberately earth the uTester's 0V rail so that any other accidental contact to earth will annoy the uTester far more than the PC.