identifying a bad heater cartirage ?

Hi guys, I have had a few good prints in the last few weeks and on Friday a roll of kapton tape that I had ordered arrived (I wanted to re tape the thermistor). I played around with the printer that night, the kapton tape started smelling and I took the heater cartridge out several times while trying to use smaller strips to attach the thermistor (the kapton take must have been bad, but I found that using small strips away from the cartridge as mush as possible worked fine).

Today I went to fire up the printer, the heated bed got up to temp - the machine homed fine, but the hot end did not heat up - the e3d fan and the bed fan - which are both connected to the +12v line for the hotend worked until I turned on the hot end then they stopped-

I have to replace the heater cartridge don't I ?

the voltage between D10 (I'm using a RAMPS board) and the + pin is 11.8V when I have turned on the heater and 9.6V when I have not



any help would be much appreciated

Disconnect the extruder, then measure the resistance of the heater. Also measure resistance to GND, which should be infinite.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Thanks Traumflug , the resistance across the heater is 4.2 Ohm , the resistance to ground was infinite (because I disconnected it -- is that right ?)

Could it be anything else ? should I just buy another heater --- is $5 too cheap ? is there any buying guides

A 40 watt heater should be 3.6 ohms. A 4.2 ohm heater will work fine giving 34 watts.

So do you have any idea why it wouldn't be working ? -- it was heating fine before I took it out and replaced the Kapton tape

If the heater measures 4.2 ohm then it isn't the problem. If it is connected properly then I would think the next most likely failure is the mosfet. Try measuring the voltage across the heater when you turn it on. My first suspicion would be a bad connection.

I think the fan wire may have shorted out - long story - ill check the mosfets

Edited 2 time(s). Last edit at 06/29/2014 09:40PM by Jerms.a320.

Thanks so much, the voltage from pin 1 and 2 is 10.75 V from pin 2 to 3 is -10.75V

I also found this


[www.printrbottalk.com]

this is my problem .... I have to replace the mosfet


Thanks so much

Edited 1 time(s). Last edit at 06/29/2014 09:43PM by Jerms.a320.

I'm in South Australia, our local electronic store is Jaycar, here is there list of mosfets -its hardly a list- (http://search.jaycar.com.au/search?w=MOSFET%20N-CH%2060V%2055A%20TO-220&view=list) ... I understand that Mosfets are a type of transistor , but ive got no idea what to buy , any help would be fantastic


thanks

jaycar hasn't got any suitable mosfets

better off going to rs components and look for any of these IRLB3813, IRLB8743, FDP8870, AOT240L, CSD18502KCS

heres one link to get you started

best part is in australia you get free delivery

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Thanks,

I missed some from jaycar -- check this link [search.jaycar.com.au] . What are the requirements for the Mosfet on the ramps board ? .... At the moment I understand they have to have a "low" gate source voltage (so that the microcontroller can activate the transistor) and they must be able to receive the current for the hotend without overheating (I don't even know how much current it need to receive)