Will this MOSFET be enough to supply Hotend

My hotend transistor broke. This is the only one I can find locally as I need it today.

Link:[www.radioshack.com]

Data Sheet:[www.radiovilag.hu]

I don't think it will do too well.

Are you using a RAMPS 1.4?

If you look at figure 6 in the data sheet, you will see with a gate voltage of 4V it hasn't even started turning on. With a gate voltage of 5V (which is what you would expect from the Arduino driving the FET), it is only starting to turn on. You could expect about an amp. If you have a J-head like I do with a 5.6 ohm resistor, the power output you would get with one amp is P=I*I*R = 1*1*5.6 = 5.6W. Normally, the 5.6 ohm resistor in the J-head would want the full 12V and the output power would be V*V/R = 12*12/5.6 = 25W. You will be nowhere near this.

So what can you do?
I had a look at the RadioShack link you gave. In their list of MOSFETS, the one you mention (IRF510) comes up first, but the second one looks good (NTE2985). N-channel enhancement mode, same pinout, gate threshold 1-2V, and with a gate voltage of 5V you get an on-state resistance of about 0.05 ohm (lower than the IRF510 by an order of magnitude!).... But it's not in store so that probably means it's not an option.

Are you running two extruders? If you have a RAMPS 1.4, it has three MOSFETs. One for the heatbed, and one each for the two extruders. If you only have one extruder then you have a spare on the board already! Use that one.

Maybe another option, if you can only get the IRF510, is to run two (or more) in parallel. Buy a couple of them. find a way to solder their pins together (beware that the Drain also connects to the tab, so be careful that nothing touches it that shouldn't). It might work (no guarantees - it's not really made to work at low gate voltages).

I am using ramps 1.4 with a single extruder. How could I switch to use D9 for the extruder and use another power source (not on ramps 1.4) for extruder fan, or omit the fan all together?

I connect my extruder fan to posts labelled 12V-AUX. They are just near diode D2, near the fuses. You could use that too.

Connecting the extruder to D9 could be done a number of ways. Maybe it's possibly to swap it over in software, but I don't know how to do that (maybe someone else here will know). You could always remove Q2 and resolder it in the place of the failed Q1. But that isn't as easy as it sounds as it is hard to get at the them and the ground plane sucks a bit of heat away from the soldering iron (maybe it's not so hard if your iron has more grunt than mine).

Looking at the schematic and the board layout (both available online), another way might be to:
1. remove the dodgy FET Q1 (which you will have to do anyway eventually), then
2. patch the gate from Q1 (now removed) to Q2 (the FET driving the D9 output). Make sure whatever you use doesn't short to anything else.
3. remove resistor R14.

I always keep a few pieces of cat-5 cable in my electronics kit. The cable strands inside are insulated, easily stripped and perfect for small patch jobs like this.

good luck

The NTE stuff is probably not stocked in the store. For this stuff, you have to use a low gate drive device to ensure that it is hard on and not in its middle range and playing resistor. This is why PWM is great for heat regulation as the FET is either hard on on hard off and dissipates the least amount of heat possible.

If you have two extruder drivers and are just using one, recompile the RAMPS/Arduino code to use the other extruder as the main one and reload.