Topic: F1 fuse on RAMPS 1.4 overheating, causing thermal runaway
So, I hadn't done much dual extrusion with my RAMPS 1.4 board lately, but today I tried a few dual prints (smallish, ~40 minute jobs), and after the first one succeeded, every print using both extruders started failing 15-20 minutes into it with a "Thermal Runaway" error from Marlin.
It's not getting too hot -- in fact, the hotend actually stops heating properly and starts to cool down to 160-165 before the error message appears.
Prints using only one hotend at a time are working fine, so it doesn't appear to be a loose connection. I was thinking it could be an issue with my power supply failing or overheating until I noticed that the F1 fuse (the smaller of the two yellow fuses near the power input on the RAMPS board) was getting really hot, and the LED for the hotend MOSFETs were only lighting up sporadically while this failure was going on.
So it sounds like I have a failing component or two on my RAMPS board from what I can tell. Question is -- is it more likely the MOSFET that's failing, the fuse, or something else? It sounds like something's drawing too much current through the fuse. I would hope it's not my hotend heater that's failing as it's practically brand new (E3D Lite 6), but I could see that being a possibility too.
If it turns out to be a component on the RAMPS board, I'd be comfortable fixing that myself, but I might start out just replacing my RAMPS board wholesale (I might even have a spare one somewhere I could swap out), but eventually I'd want to fix this one. Before I rip the board all apart and start testing components, I thought I'd ask here in case someone's hit this issue before or has ideas about which components could be failing.
I'll note that the hotend seems to heat up and prints fine up until this temperature failure, so if it is the heater failing, it's not quite dead yet.