Anyone else have to replace the heater element on one of these? I just did, and it is a relatively painless job... Except for the fact that the temp sensor is a thermocouple which is not marked for polarity in any way.
If you get it hooked up backwards you don't get a screwy temperature reading (as with most industrial TC systems). You get a display that stays stuck on 77F while the heater warms up. After a few seconds the unit drops out on a fault. Presumably when there is no response from the thermocouple within X seconds,CPU sets an error (and hopefully) shuts down the element to prevent overheating. Nice to see that they did put some thought to protect against this (or a shorted sensor), as well as having a separate fault for an OPEN thermocouple.
The replacement heater comes with tiny brass crimp sleeves, which need to be used because the thermocouple and heater element wires are not copper, and won't take solder easily. I did flow solder over them after crimping to fill any voids left in the dodgy crimps.
I replaced my heater because the tube got clogged with something that is resistant to melting, presumably oxides and carbon from flux, etc. Got most of it reamed out with a drill but need a longer drill to get it all out. Hopefully can save it for a spare. Not sure how it happened, as I'm pretty religious about running the cleaning rod through the thing.