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I messed up my PCB design when I made a change of FET-model. Now the Drain and the Source pins are swapped and it seems that there are no TO-220 models made this way (1-Gate, 2-Source, 3-Drain). Are there any pinouts like this, or do you have any other solution? Making a new PCB is too expensive, since many other components where soldered before discovering this mistake.

schematic

simulate this circuit – Schematic created using CircuitLab

enter image description here

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  • \$\begingroup\$ How many boards have you built up? Is it using a heatsink? \$\endgroup\$ – DiBosco Aug 8 '17 at 9:03
  • \$\begingroup\$ @DiBosco It's only this board but it's a student project and we're pressed for time and money. So my options are finding a new component that fits the TO-220 footprints with correct pinout for my error, or I can try to fix this error by bending the legs or using wires connecting component and board. We don't have a heatsink on this part. Thanks \$\endgroup\$ – Sheepwall Aug 8 '17 at 9:09
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    \$\begingroup\$ If it's a one-off and no heatsink I think you already came up with the answer. :) Get some heatshrink on the legs to insulate them and bend them as best you can. You should be fine even if it's not as robust as it should be. We've all been there and done that! \$\endgroup\$ – DiBosco Aug 8 '17 at 9:11
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    \$\begingroup\$ The pinout for most TO-220 MOSFETs is G,D,S so you will either need to modify the PCB or bend the legs appropriately. You can usually find a neat way to do this but we would need to see your PCB layout to suggest how. \$\endgroup\$ – Warren Hill Aug 8 '17 at 9:12
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    \$\begingroup\$ As it's TO-220 with 2.54 pin space you can easily make a little adapter with a simplest protoboard. Cut just a small piece from it, solder your transistor, solder three pins (cut three contacts from the pin strip), connect them appropriately, and solder those pins to the PCB. \$\endgroup\$ – GAttuso Aug 8 '17 at 9:58
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You have several options:

  • create new board with proper pin order (expensive as you wrote, but it's the "cleanest" solution)
  • find MOSFET with order of pins you need (it is hard to find such MOSFET with proper parameters)
  • bend pins (carefully, so you don't break them) - solder Source and Drain pins directly without bending, and bend just Gate pin towards limiting resistor
  • use wires and heat shrink tubes (so MOSFET is not soldered on the PCB)
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