MakerBot Industries

Well that sucks. I'll see if I can test it when I get home. I followed the instructions perfectly and got the 6 ohms exactly right (took about 4 tries) just so it wouldn't burn out. So, if I buy a new board, it will just pop again, most likely. I guess I'll just have to wait until they get more Mk5 extruders in stock and just upgrade at the same time so I don't have to keep buying new boards. OR I guess I could just keep replacing the B MOSFET … I guess it wouldn't hurt to try.

As for my drifting X, on the last print I was printing a very Y-Long piece and I noticed on the long Y passes a ticking sound. I thought the Y belt was now slipping but that wasn't happening. I then, by accident, caught the X stepper motor "twitching" during those sections. So, I thought "interference"! I then took the interface wires out, separated them, and then gave them a good twist. I put them back in; then, not heat! That's what frustrated me the most. I might have just found the reason my builds were drifting and NOW I can't even test it. :'( I'll just have to get the extruder board back up. [I hope I can get the MOSFETS at RadioShack so I can work on it over the weekend ;) ]

I just had the same problem two days ago. Searching in the forums i concluded that the FET died (because of a short, oups!). Aaaargh extruder controllers sold out in the shop and not a clue of smt soldering… I tried anyway the replacement of the FET (used C) but it didn't work neither, finally and to make it short I just took the solder and touch with it the FET, the led and the resistor for B+/-. My extruder is up&running again!

If it tests dead and you can't find the right MOSFET locally, http://www.makergear.com has the right ones in stock.

You might also consider a good heatsink for the A & B fets, which are the HBP and heater ones. I used http://www.newegg.com/Product/Product.aspx?Item=N82E16835708011&cm_re=enzotech_copper_heatsinks-_-35-708-011-_-Product on my controller. Newegg is out of stock ATM but google can probably fix you up with a place to get them.

i added the heatsinks to mine a while ago as well and they have been working really well. they get really hot too, hotter than the mosfets ever seemed to get. I cant hold my finger on it after 4+ hours of printing. i put a tiny fan on them and have has zero problems with it.

I am not running the relay yet (i have the kit just haven't put it together yet)

I just had an idea, but I don't have any idea how to execute it. Instead of desoldering and resoldering and replacing MOSFETs, can't I just tell the board to use A or C instead of B to heat the extruder head? Would that be in the firmware or perhaps the ReplicatorG drivers or even the GCode? OR am I just dreaming an impossible dream?

I guess that will not work. B is wired up to a PWM and the other two are not. (May be it would be possible to use A, thermistor wired to A6 in the board? and tell to skeinforge to heat the HBP and not the extruder?)
Did you already tried to check the MOSFET without desoldering anything?

I didn't even get a chance to test it last night and probably won't tonight either. I'll have to start working on it on Saturday when, hopefully, eveything calms down a bit, and from what you mentioned, it looks like I'm just gonna have to replace it if it tests bad. You mentioned earlier that the C MOSFET wouldn't work for you. What did you do to fix it? Did you solder a jumper between two other components?

MOSFET C didn't work neither because the MOSFET was not the bad guy in this history. I concluded to quick that it was burned/broken/whatever from reading the other similar posts in the forum. Jumpers… I'll would not do it unless you are 100% sure you're not building unwanted bridges, so making shorts, here and there.
Test first the MOSFET itself with a multimeter, it takes one minute. As you say, if it test bad you'll need to replace it and then, and while you don't get a replacement, you can use C (or A if you don't intend to use an HBP in the future).
If it tests good (i want to believe it will) you can forget about desoldering and resoldering things. In my case it looked good and the connections from the MOSFET to B, LED and Resistor where also looking good… to get crazy.
The solution that worked to me was touching with the soldering iron: MOSFET, LED, Resistor and also B+/-.
No need to desoldering no need to add solder neither (however, add some solder could not be bad neither if just touching doesn't help).
I guess that I was getting connectivity between elements because the tips of the multimeter were pushing down the component to the path, but that's just a guess… Goog luck! and let us know how it's going on

Oh, so you just re-flowed the solder, and it might only be a bad connection. Hmmm … Fingers crossed! :-D Thanks!

I'd still drop a heatsink on it…

Well it's a moot point anyway. I just got through trying to reflow the solder and no luck. Still dead. I did try to test it, but I don't know if I was doing it right; so, I went ahead and tried to reflow the solder as it did look a little light on the connections. They are definitely connected now. :-) I guess this is a good time as any to just upgrade to the Mk5 and buy a new board along with it as something in my Mk4 build might just blow the next one as well. I don't have the tools (nor the skills) to replace those components, and it will probably save me a headache or two just to get a new one. I'll definitely buy some heatsinks or this could get VERY expensive. Maybe those should be added to the kit, eh… ;-)

In any case, thanks for all of your help. It was a good try. I'll just wait until the shop has some in stock and work some more overtime.

Sorry to read that :-( don't forget the Relay Kit together with the heatsinks.

In the meantime if you got some time… quick test: enable the fan from the control panel in ReplicatorG. Does the C led light? then C MOSFET is ok. I didn't had the skills neither and my only equipment: an ordinary 40W iron solder and tweezers. I trained a little bit with another board that was to throw away and then I did it without much problems in the extruder board.

I had an idea to epoxy a popsicle-stick or something to the component and then use that to pull it off as I desolder it. I haven't tried it yet, but depending on how long it takes to get more boards in stock, I might just give it a go and replace it with a new MOSFET from the Internet. :-)

I did it just with the tweezers pushing the MOSFET to one side as I was heating the contacts, the only thing wrong with this is that it can get too hot but… it's to throw away anyway, isn't it? ;-)

I just had problems again with my extruder :-( 1st I got a short, then the issue with the MOSFET, for two times I've seen the ABS getting out from the PTFE at the heat barrel level and now it looks like something was wrong with the connector between the cable and the nichrome. It's the 5th time I re-do the extruder, hope this time will work longer :-) as every time I have to rebuild it, it gets more and more damaged (the insulator retainer looks like it's not gonna stand much more assembly/disassembly, the nichrome is loosing isolation quite fast, …) I don't give up, I'm gonna make it work :-D