Ontopic The 3D printing thread

If the thermal pad blob on the back of the board was touching the case, that'll cause a drain to ground short, which would be the same as a shorted MOSFET. Still measuring a short with the board pulled?

But if the MOSFET is dead anyway, specs are gonna be...

Package that matches whatever's on the board (though you could ghetto rig a TO-220 on there if you wanted to)
Vds rating of 40V or better
Logic level (5V) compatible gate
Rds(on) of 20mohm or better at Vgs=5V - this way the FET dissipates 1/2 watt at 5 amps, so it shouldn't burn up even if they totally fucked up the heatsinking.

If there aren't any clamping diodes across the terminal blocks for the heaters/fan, grab a few shottky diodes too. 1A/40V (like MBR140 or MBRA140 or whatever) should work fine. Put them across the output, cathode to +24V, anode to output.
 
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gee said:
If the thermal pad blob on the back of the board was touching the case, that'll cause a drain to ground short, which would be the same as a shorted MOSFET. Still measuring a short with the board pulled?

But if the MOSFET is dead anyway, specs are gonna be...

Package that matches whatever's on the board (though you could ghetto rig a TO-220 on there if you wanted to)
Vds rating of 40V or better
Logic level (5V) compatible gate
Rds(on) of 20mohm or better at Vgs=5V - this way the FET dissipates 1/2 watt at 5 amps, so it shouldn't burn up even if they totally fucked up the heatsinking.

If there aren't any clamping diodes across the terminal blocks for the heaters/fan, grab a few shottky diodes too. 1A/40V (like MBR140 or MBRA140 or whatever) should work fine. Put them across the output, cathode to +24V, anode to output.
Click to expand...
I measured after pulling the board.
 
gee said:
Try just twisting it off... it's probably just silicone, it should give way before anything else breaks.

Take a pic. I'll go looking up some part #s. What sort of electronics stores do you have in your area?
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I got the heatsink off, it was just silicone blobbed on there.

The MOSFET is definitely bad, looks like it let the smoke out.

I can see 3 MOSFETs on the board under the heat sink, they're all labelled AOD522P, which I assume leads to here, a TO-252 MOSFET with a Vds of 30V. Got a recommendation for a compatible MOSFET with better specs than that?

edit: there's two rows of numbers, but google didn't help me on the second one, which looks like "GA4B1D", or "GA481D", or "GA4810".
 
Jehannum said:
I got the heatsink off, it was just silicone blobbed on there.

The MOSFET is definitely bad, looks like it let the smoke out.

I can see 3 MOSFETs on the board under the heat sink, they're all labelled AOD522P, which I assume leads to here, a TO-252 MOSFET with a Vds of 30V. Got a recommendation for a compatible MOSFET with better specs than that?

edit: there's two rows of numbers, but google didn't help me on the second one, which looks like "GA4B1D", or "GA481D", or "GA4810".
Click to expand...
Odds are it's the AOD522P, and the second row is date/batch/factory/whatever.... and yeah, using a 30V MOSFET at 24V... design margins! I'd replace all three.

There's piles of suitable FETs to choose from... all comes down to whatever your electronics shop has in stock.
Infineon IPD50N04S4L-08 is one option - 40V, 8.8mohm @ 4.5V, and a pretty low gate charge so it should switch on/off pretty quick.

What kind of selection do they have? I s'pose walk in there and hit me up on facebook messenger with some part numbers that they've got, I'll go looking up datasheets.
 
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Valve1138 said:
Whats a good turnkey 3d printer? Can I get one for $500 that doesn't require me to fuck with it to get it to work well?

I'd like to be able to print custom tap handles, and maybe some triathlete bike accessories.
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What size items? $500 is probably doable, but the only ones I know of in that range are like 4x4x4" or so.

Might find factory returns somewhere?
 
Valve1138 said:
Whats a good turnkey 3d printer? Can I get one for $500 that doesn't require me to fuck with it to get it to work well?

I'd like to be able to print custom tap handles, and maybe some triathlete bike accessories.
Click to expand...
If you want to spend zero time fucking around with shit, add $100 and get a Prusa MK2S kit.
 
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Jehannum said:
Went super ghetto and did a daughter board with some through-hole mounted NTE 2986 MOSFETs.

I'm getting ready to test print now. Pray for me.
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Might work, but assuming 35mohm on resistance at 4.5V gate drive out of the datasheet and a 5A heat bed load, it'll dissipate 875mW and a bare TO-220 package will heat up by about 50 degrees C. Watch out for burnt fingers...
 
gee said:
Might work, but assuming 35mohm on resistance at 4.5V gate drive out of the datasheet and a 5A heat bed load, it'll dissipate 875mW and a bare TO-220 package will heat up by about 50 degrees C. Watch out for burnt fingers...
Click to expand...
I'm going to pick up some M3 hardware after lunch so I can sink 'em to the case.

Really, this is just a stopgap until the upgraded board is available.
 
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