The thermocouple is either shorted to the heater block or connected backwards at the motherboard. Try swapping the wires in the connector but also make sure the thermocouple is electrically isolated from the heater block. A good way to do that is a couple layers of kapton tape, the same type that comes with the makerbot for the print bed. If you have an ohm meter unplug the thermocouple from the motherboard and check both leads for continuity to the heater block and also make completely sure neither of the heater wires are touching the heater block. The first one probably smoked because the 24v to the heater made contact to the heater block and then went down the thermocouple wires. The original board is probably still repairable, I’ve fixed a few of them now, it usually blows the chip on the board that is used to interface to the thermocouple. Hopefully you haven’t killed the new one yet! First step though check for shorts and swap the thermocouple wires in its connector block, the green block that you tightened the wires into and plug into the motherboard. If your still seeing the same problem chances are the chip was damaged. The Rep 1 is the best makerbot made in my opinion, I have over 2300 hours on mine with only a few minor issues. And I can repair these motherboards, I’ve fixed at least a dozen now with blown chips. Do you still have the old motherboard? If you get this one working with the stuff I told you to check I would offer to look at your old board to see if it can be repaired. Then you would have a spare, replacing the chip and usually one surface mount resistor fixes it and parts and labor I do these all the time for far less then the cost of a new board! Definitely not time to replace it, but if you decide to go that route let me buy it for parts or repair! Lol I hardly ever see a used rep 1 for sale, seems like those who own them never want to sell them! I’m always watching eBay for another one to fix up.
Also one other tip I didn’t mention in my last post. Never try to replace a nozzle cold! Always do a preheat and remove the nozzle hot. Trying to remove it cold is a guaranteed way to shear one off! I bought a metric nut driver, looks like a screwdriver, for the nozzles. Then if I have to remove one I do a preheat screw it right out and set it on a piece of metal or the sponge for my soldering iron. It’s a pain to work with them hot but you won’t damage one or the heater block.
His problem isn’t firmware now though, cause if he positions the carriage on the X and Y stops and then starts a print he doesn’t get crashing, meaning the offsets are correct and its not going to far.
The key to troubleshooting this is in his last reply to me is that if he manually homes the X and Y it works, which means its not getting a correct homing. Also when he homes the axes the X doesn’t return fully home.
On the Rep 1 this is a very common problem caused by the stepper motor wiring coupling to the stop switch wiring since everything is unshielded wiring. Moving the X-Axis stepper motor wiring from the front right corner to the back right corner is the common solution and was even being suggested by Makerbot support at one time.
On some i have even gone so far as to make a shielded stop switch cable, which also stops this problem dead. To do that i take the braid from a bad thermocouple and pull out the thermocouple and use it to make a shielded cable for the stop switch.
Ok I will try the rewiring later tonight. I am also having other issues though.
I set the heater settings to 215, and it is constantly going up to 230 when i am preheating.
For example, if I do load/unload, it heats up to 230, then waits to go back down to around 215 and it will begin unloading/loading. I never had that happen before all this shenaniganry.
Also, when I try to do a print, the heat actually goes DOWN while printing. I saw it go down to like 189 during the print (still set at 215), and then it starts jamming up, maybe because the filament is less viscous.
Apparently, I am very good at keeping myself from printing correctly.
Ok for the preheating, go to Info and Settings then Preheat Settings, are those numbers set correctly?
Does it go to 230 and stop? No errors? If it overshoots too far and its correctly reading the temperature it would pop up that there is a temp problem. But it sounds like its just hitting a preset temp.
The temp going down while printing could be a number of factors, cold room, air movement it cant keep up with etc, but it could also be a temp reading issue yet with the thermocouple.
If moving the stepper motor wiring doesn’t fix the homing on the X axis you could still have a bad or intermittent X-stop cable for the X axis switch. I have had that happen before as well, it causes really weird intermittent issues, but from what you described it sounds like the problems i had with the interference issue.
I got one print out at a an average of about 220 degrees or so in PLA, at it was all warped and everything, but at least it finished wih no carriage jam or nozzle jam. It was a bit more consistent with the temperature on that particular print. I still think I may have even damaged this thermocouple because it jumps around in temperature like 10+ degrees on the temp screen with no transitions. I can’t actually believe that the actual temperature is jumping around like that. I have a source for a $20 thermocouple, so I’m going to try that. Still had no luck with the firmware update. I tried 20+ times last night and I got the same error. I wonder if it’s just fruitless to update it on this particular board.
What are you getting for an error when trying to update the firmware?
Which version of firmware is in it now?
Also on the thermocouple a new one is probably a good idea but also i would check to make sure its insulated at the heater block. If you have a multimeter set it to the continuity test and unplug the thermocouple from the mainboard and check for continuity from the mainboard end to the heater block its attached to, and check both wires. Continuity from the heater block to the thermocouple can cause some weirdness as well due to static charges and such, its also a good way to blow up the chip for the thermocouple. At the very least if you don’t have a meter to check it make sure the end of the thermocouple is wrapped in a layer of Kapton tape, the gold tape that you use on the print bed, and then it should be electrically isolated. If your thermocouple has a ring terminal on it and its not the factory one i would also wrap a layer of kapton tape around the ring terminal so it covers it completely then pierce a hole in the tape in the center of the ring terminal for the mounting screw and reinstall. A lot of the cheap thermocouples i have bought off eBay with ring terminals were just crimping onto the end of the thermocouple and were not insulated. The way it should be done is the thermocouple is glued into the ring terminal with non conductive thermal adhesive. But its hard to find good ones that were done right!
My stock Makerbot thermocouples are just a bare end wrapped in kapton tape and pinched under the washer on the mounting screw, they still work great, i guess they were a lot better quality then most.
