1 Topic by ne14pez

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Topic: Help Extruder Temp. Lost Control

I was soldering leads for an extruder fan onto the board where it says "fan" (as was suggested in other forum feeds).

I must have done something wrong because now whenever the printer is plugged in at all, the extruder temp. keeps rising, even up to 260C (when I smelled something and discovered it was happening)  Repetier cannot control the temp. any more.  It is just always "on", even when heat is off.  How do I troubleshoot this?  Thanks.

Printer: Slidoodle 3 (8-13 purchase), Motherboard REV-E

2 Reply by 2n2r5

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Re: Help Extruder Temp. Lost Control

Sounds like your MOSFET gate is stuck open. Time for a new MOSFET.

SD3 w/ mods:
Glass bed with QU-BD heat pad upgrade, threadless ballscrew w/ 8mm smooth rod, spectra line belt replacement, lawsy MK5 extruder, Lawsy replacement carriage, E3D hotend, Ramps 1.4 w/ reprap discount controller, DRV8825 drivers, 12v 30A PS, Acrylic case, Overkill Y-idlers, Filament alarm, Extruder fan + more.

2n2r5's Website

3 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

Could I have damaged that by soldering the fan?  Is there a way to test if in fact it is the MOSFET that is broken?

4 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

I checked voltage on the MOSFET directly above the connector that goes to the heater (which is unplugged for now) and turned heater on and off in Repetier to see what changes.   I compared the voltage difference across the left-most pin and the middle pin.  When heat is "off" the difference is 2.7V, when heat is "on", it rises to 4.7V.

As a comparison, when I do the same thing with the heat bed MOSFET, it is -12.7V when off, and 4.7V when on.

Does that imply bad MOSFET?

5 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

Sorry, I should have provided voltage measurements relative to to input power.  OK, so here they are:
Heater Off: pin 1 (2.7v), pin 2 (0V), pin 3 (0V)
Heater On: pin 1 (4.7v), pin 2 (0V), pin 3 (0V)

My electrical knowledge is minimal, but isn't the middle pin the "signal" voltage?  It didn't change at all, so doesn't that mean that the MOSFET is not getting the proper signal?  For comparison, the Hotbed MOSFET's middle pin is at 12v when on, and 0v when off.

6 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

I removed both MOSFETS and I put the heatbed MOSFET on where the extruder one was, and still doesn't work.  I put together a simple circuit to test the MOSFET, and it seems to be fine.  I can turn on and off an LED but giving it gate voltage.  Is my board fried?

7 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

I really need some help here.  Solidoodle CS says they've never heard of this before either.  My MOSFETS seem ok, but temp still increase indefinitely.  Can/should I flash the firmware?  Where do I get the firmware?  Thanks.

8 Reply by jason_

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Re: Help Extruder Temp. Lost Control

You didn't bridge q3 to the fan pinout did you? first thing I would do is reheat all the solder that you put down and suck or wick it off.  Recheck to see if you still have a problem

9 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

I didn't bridge q3, but now that you mention it, one of the q3 pins looks funny.  It is missing solder and has that "burnt" look to it.  It is possible that I damaged it unknowingly.  I just tried adding a tiny drop of solder to the leg and letting it seep in there (very carefully!) to hopefully make sure there is contact.  Unfortunately, there is no change to the symptoms.  Based on what I saw though, I think q3 may be fried.  If this is true, would it cause the symptoms I describe?  What are the specs?  Perhaps I can replace it.  Thank you.

10 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

Just checked for continuity across the 3 legs of that q3 transistor and there is continuity between all legs.  Transistor is toast!  What do I do now?

11 Reply by jason_

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Re: Help Extruder Temp. Lost Control

Does this look like your q3?

12 Reply by ne14pez

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Re: Help Extruder Temp. Lost Control

Yes, it sure does.  I just sent my board back to Solidoodle.  We'll see if they are willing to replace it.  I really hope they do because I don't want to spend $180 on a new one!

jason_ and 2n2r5, thank you for your help with this.  I'll post the outcome when I find out.

13 Reply by 3d-oodler

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Re: Help Extruder Temp. Lost Control

I haven't ordered from them, but others on the forum have.

geeetech.com runs weekend specials.

You can get a replacement sanguino board there for $40 +shipping (if the other route doesn't work out)

http://www.geeetech.com/2013/09/weekend … on-wk37-2/

Or move up to RAMPS for $80
http://www.sainsmart.com/starter-kit/3d … eprap.html

14 Reply by COASTER19

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Re: Help Extruder Temp. Lost Control

Could something as simple as replacing the electronics cover without unplugging the board from the computer's USB cause this? (the screw might have bridged two pins when being put in the hole)