Hot End Not Coming Up to Temperature

[grasshorse]

Hello,

Saw another post like this, but thought I would put mine out there as well.

Just setup my MAX and was about to configure it. I was having some initial problems with the thermistor, but I worked those out. After that I brought the Bed and Hot End up to temperature. I had Repetier host running and I switched to a Firefox browser while everything was heating up. Came back and the MAX was frozen, Hot End and Bed stopped heating and the machine wouldn't home. Restarted MAX and Repetier and the bed would come up to temperature and the machine would home, but the Hot End will not. 15Amp fuse is fine. Looks like the thermistor is accurate.

Did I just fry my RAMBo as well?

I put the resistors in so they slid in smoothly to the Hot End. They were not overly snug. Is that what did it? It drew too much current from the board and pop? Is there something else I can look into?

All the best

[JohnStack]

Fuses. Just went through this.

There are tiny ceramic fuses on the Rambo. I would check those. Pop those out carefully and check for continuity.

You can check their continuity while they're on the board if you think you have a steady hand. I don't.

When/if you put them back in, be sure not to bend their mounting fins. I did that too - giving me a false negative for a burned out board.

[Eaglezsoar]

I agree with John about checking the ceramic fuses but also measure the resistance of the resistor in the hot-end.
It's possible that it is now open and will measure as such. It would not hurt to check if Repetier host is not set to
dry run mode, but I think you said the heated bed is heating so I doubt that repetier host could be the problem.
If you find that the resistor is open, do yourself a favor and invest in a 40 watt cartridge heater made for the hot-end.
Those resistors just short out too often. Best of luck diagnosing the problem and be sure to let us know what you
discovered.

[grasshorse]

You got it John. The 5 Amp ceramic fuse is blown for the Hot End. I'm going to take your advice Eaglezsoar and purchase a couple of the 40 watt cartridge heaters. I assume that the root cause for the fuse blowing to begin with. Since I have to wait a week for the fuses, I might as well order the cartridge heaters as well. Is it a big pain getting all of that RTV off the head then?

In the process I was (trying) to follow John's troubleshooting process that he had in his post and I think that I may have fried the Heated Bed output. I turned the heated bed on and tried to read the voltage off the board and when I lifted I heard a pop. I was hoping it was the fuse, but I since learned that the bed uses the 15A fuse which still looks fine. Since then I can't get the heated bed to come up to temperature, nor does the LED for it come on. Oddly I see that voltage is coming out of the board.

If anyone has any ideas on that I would love to hear them. I think I pulled a bone-headed move.

Thanks,

[Eaglezsoar]

If voltage is coming out of the board and is going to the heated bed and is at 12 volts then the bed has to heat up...unless...you fried a trace on the
heated bed. TURN OFF THE POWER WHEN YOU ARE PROBING. Check the resistance of the heated bed - THE POWER IS OFF, RIGHT? If the heated bed
shows an infinite resistance then you are going to have to remove it and see if a trace is open. You sound as though you know how to troubleshoot but
please remember that one rule, turn off the power unless you are trying to measure voltage then be extremely careful. I not only turn off the power but
I also unplug everything from the wall socket. Please let us know what got cooked this time.

[grasshorse]

Only thing that got cooked is my pride. Near as I can tell, when I probed the board for power to the heated bed, my probe loosened the screw to holding down the wire to the connector. I shut everything down, tightened the wire and bingo it worked again. Now all I have to do is wait for the fuse and cartridge heater. Really can't thank both of you enough for your help.

All the Best,

Steve

[JohnStack]

That's a relief.

I didn't think to tell you "with power off" - since you are essentially bypassing the fuse by doing that.

I'm changing my title from PrintMaster to Use Caution with this Printmaster....

[grasshorse]

Not at all John. You are certainly a Printmaster! I understood your instructions very well and they were helpful. I had the power off for all steps other than probing for power and assumed it should be that way. When I pulled the fuses the power was off. Near as I can tell the popping I heard was when I pulled the probe off the screw and the wire became disconnected from the connector. I think my post before was poorly worded were I was basically asking "did I do something really stupid?" I was stepping a little out of my comfort zone and the "(trying)" is entirely a comment about my abilities and not your instruction, help and insight. Again, thank you very much!

Steve

[Eaglezsoar]

Hey, glad to hear it was something simple. I spent most of my life in the electronics field and I am over 60...take a guess how many times I made mistakes...you can't count that high.
Chalk it up to a learning experience and move on. I'm glad that you decided to go with the cartridge heaters they are great compared to the resistors. They also make screw in thermistors
that screw into a 3mm hole, the problem is that you end up having to drill out the thermistor hole with a 2.5mm drill bit then tap it with a 3mm. If your hot-end allows for that and you
have the tools I would recommend them but few have the right tools so a regular thermistor is usually used. If interested do a search on ebay for threaded thermistor, there is a link
somewhere on the forum. The regular thermistors are fine as long as you use the tiny UHMC tubing to cover the leads. As far as removing the RTV you are just going to have to cut off
what you can. I did see RTV remover on Amazon but you should be able to get most of it off by hand. Keep us up to date as you progress, that's what we are here for. Here is the link
for the screw in thermistor if you are interested, but they are on vacation until the 19th....http://www.ebay.com/itm/321108299432?va ... 1439.l2649

[geneb]

I get the impression that you installed the resistors in the hot end without wrapping them in foil first. Is that correct?

g.

[grasshorse]

I did wrap the resistors in aluminum foil. I wrapped them until they wouldn't fit into the holes in the hot end, then I cut an inch off the length of foil wrapped the resistors again and installed them. Oddly, that 1 inch less foil made it so that they were not a snug fit in the hot end. I was worried a bit about that. Ultimately it was that the resistor wires were shorting against the sides of the hot end. I replaced them with one 40 watt heater cartridge and everything in regards to the hot end has worked flawlessly. That said, when I installed the cartridge and spread the wires as they come out of the hot end the shielding didn't fully cover the exposed wires coming from the cartridge. So I just put a dab of RTV on them to make sure they wouldn't short out in the future.