Still nothing as shiny as a Fluke 77 I saw from the council electricians, who tried to use it to measure the primary of a LV distribution transformer. Seems 11kV was a little too much for the 600V rated meter, which still was in one piece, though there was not a single trace left on the lower side of the board below the display, all the copper had been evaporated off the traces, and deposited as a nice shiny film on the case. Just the component leads and the solder bumps, with green silkscreen removed where the traces had been underneath. Incidentally the PTC thermistors they use are normally nominally 4k7, so a 4k7 resistor normally will work as a test, as often the units also have shorted probe detection in the more complex units, which use a quad comparator, so will trip off if the probe resistance is outside the range of roughly 2k to 8k, which conveniently means they also work with NTC probes as well, though the PTC units do have a much better temperature trip point, as when they reach the critical temperature resistance goes from around 6k, to over 50k, over around 5C of range. Guess you will be doing a similar fix on the PLC, though I solved a dead relay (wore out at a young age, only 20k operations) by simply using the programming keypad, and moving it to the next output, as that was free, and a lot faster than removing the PLC from the hole it was buried in. Still had to drive 2 times to borrow the keypad and return it, but faster than trying to take an Omron PLC apart to get to those relay boards, buried in the top of the package.
Still nothing as shiny as a Fluke 77 I saw from the council electricians, who tried to use it to measure the primary of a LV distribution transformer. Seems 11kV was a little too much for the 600V rated meter, which still was in one piece, though there was not a single trace left on the lower side of the board below the display, all the copper had been evaporated off the traces, and deposited as a nice shiny film on the case. Just the component leads and the solder bumps, with green silkscreen removed where the traces had been underneath.
Incidentally the PTC thermistors they use are normally nominally 4k7, so a 4k7 resistor normally will work as a test, as often the units also have shorted probe detection in the more complex units, which use a quad comparator, so will trip off if the probe resistance is outside the range of roughly 2k to 8k, which conveniently means they also work with NTC probes as well, though the PTC units do have a much better temperature trip point, as when they reach the critical temperature resistance goes from around 6k, to over 50k, over around 5C of range. Guess you will be doing a similar fix on the PLC, though I solved a dead relay (wore out at a young age, only 20k operations) by simply using the programming keypad, and moving it to the next output, as that was free, and a lot faster than removing the PLC from the hole it was buried in. Still had to drive 2 times to borrow the keypad and return it, but faster than trying to take an Omron PLC apart to get to those relay boards, buried in the top of the package.