Duk’s asked me if I could take a look at a slow heating 3D Printer that never gets up to a usable temperature. Turns out one of the two heater resistors was open.
they are just 6.8 ohm 3W resistors stuffed in with RTV Copper.
luckily I keep spares on hand for my printer. I cleaned out the RTV and found a 12V 40W cartridge fit perfectly.
its 3.6 Ohms so it is a perfect match. the two 6.8’s were in parallel so that was 3.4 Ohms
i would have liked to drill and tap a hole for a set screw but there no meat on the sides…
it was a pretty snug fit and a drop of Permatex should hold it fine.
It seemed to heat quickly but had a lot of overshoot so I reran the pid calibration and got that tuned in..