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I think my RAMBo may have just self-destructed - UPDATE

Posted: Thu Sep 05, 2013 9:47 am
by GarageBay9
After getting my Rostock finally calibrated and printing reliably, I had my hands full for a few days and just yesterday finally got back to it and took a swing at my first larger print (some parts I drew up myself in 3dsmax). After clearing a plugged hotend (@&*$#^!) everything seemed to be working... for about half the first layer. At about that point, I'd ultimately get a temperature sensor error in the Repetier log and it would go into dry run mode. This had me pretty baffled, since I knew the hotend thermistor was good and it had been working fine previously, and it read correctly when probed for resistance with my meter. But the LCD panel would read "def" for the hotend, and sometimes the bed (even though the bed hasn't skipped a beat.)

Power cycling the printer to get it out of dry run mode seemed to fix it 90% of the time. Once or twice I had to power cycle it again. Thermistor kept reading correctly on the meter. I tested the circuit up to the thermistor bulb itself and back down to the board at every junction and everything looked good.

I had several failed prints yesterday where it would throw a temperature sensor error and go into dry run mode in the middle of the print; at one point I saw a temp reading on the hotend of -20C. Besides THAT, the printer was otherwise running fine when I shut it down and left it that way for the evening.

Turned it on this morning - didn't change a thing - and now the LCD screen on the RAMBo doesn't show anything except four rows of white squares. :shock: :(

HELP

--EDIT / Update--

I've narrowed it down to the hotend thermistor lead. When it is unplugged, the printer boots normally and the LCD display functions, although I get "def" readings for the temps on the hotend AND bed. When it's plugged in, white squares and nothing else. I haven't changed a dang thing since it was working mostly properly yesterday :| The thermistor is reading about 100.2k ohms at room temp, which seems off. I have my hotend set up so the thermistor, power, and fan are all on plugs (AND none of them can be accidentally swapped or plugged in wrong, bwahaha). The thermistor shows a good circuit up to the plug, and there's a clean circuit along the lines from the plug all the way down to the board.

I'm stumped. Still could use some help here.

Re: I think my RAMBo may have just self-destructed - UPDATE

Posted: Thu Sep 05, 2013 3:12 pm
by lordbinky
Sounds like you need to go over your thermistor really well, it sounds like a break somewhere either in the lead or the wire, since it gets worse while the hotend is moving.

Tests you can do are continuity/resistance tests between each of the hotend connections (between each of the heating resistor connections and the thermistor connections maybe even the fan).

You can also try process of elimination style checks like unplug the fan and heater connections to the hotend and leave the thermistor plugged in, and the various combinations of those.

It is also possible the problem may also require that the hotend be up to printing temperature to make locating the cause obvious.