RIP Heater Resistor

Well running a 5.6ohm heater resistor off a 19V and using graphite heatsink paste is not a good idea. They last for about 10 hours before being toasted quiet nicely. See attached photo's .

Thought my hotend heated up really quickly and the massive overshoot was odd.

64W into a 5W resistor = fail.

So the question is should I:

1.Use the 'standard' loose fitting 6.8ohm resistor and fire motor it in place. Still gonna draw 53W however......

2. Use the same series as the 5.6ohm tight fitting resistor, but get the 13ohm version (UB5C-13RF1) and graphite heatsink paste it in again. So it only draws 27W which is closer to the 25W draw of a 5.6ohm resistor at 12V.

For those of you interested this is the graphite heatsink paste I am using:
[nz.element14.com]
good to 400oC apparently.........

My suggestion is taquilla.

I run the 5.6r off of 15v without issue.

I have used thin wall brass tubing to make the 6.8r fit in the 5.6r hole.

Careful running the Arduino off of 19v, that is the max the regulator can handle and it gets really hot. Even at 15v it gets hot.

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Well I tried Tequila, but I just wound up in a gutter in Mexico...........

So after a short walk back to NZ, I tried this:

1. Found some old heatsinks from a after market GPU cooler system I had and thermally glued these to the Pololu's. See attached photo's. The heatsinks seem to run at about 50oC-60oC (touchable), so win there.

2. Decided to heatsink, the 5V reg, on the Audrino board, considering sublime's warning/omen. I should have realized that the heatsink would actually block the heat from the PCB heatsink, so that lasted about 5mins running time. Fail. Frustrated I got the big hitter out and replaced the linear 5V reg with a RECOM switcher reg (R-785.0-0.5). Win, runs a bit warm, maybe 25oC-30oC. Gotta love switch mode efficiency. Only thing was I had to remove the DC jack from the Audrino board, no biggie however. See photo's, and do not heatsink the linear reg, BAD idea.

3. Replaced the burnt out 5.6ohm heater resistor with 10ohm. Seems to work better now (time will tell), not so much overshoot when it is heating up. Reflecting on it I think I did not get enough graphic heatsink paste on the 5.6ohm one, created a hot spot and caused the failure.

So win for now, time will tell however, how good my repairs are.............. Back to fixing my extruder and doing some drawings.

Sorry to hear the regulator died but happy to know the result "Do not use a heatsink on the regulator". The new turino board is being made to handle 35v which will be nice for us RepRappers.

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I've been having similar problems. Make sure you are using PID drive (not On/Off) and set the maximum drive level much lower in your configuration. If the system sends a low enough duty cycle drive power, the resistor should not overheat while waiting for the thermistor to respond.

Good luck!