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How to replace Q507

 

After the great BS170 meltdown on my QMX, I'm down to replacing Q507 (Q503 and the BS170's have been replaced and look good). I do not have a hot air rework station - only ChipQuik. It looks like the drain is a pad, not directly accessible with a soldering iron.? Suggestions on how to replace Q507 with the materials I have ?
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73,
Steve, N2IC
 

Steve, if your solder iron has enough power (at least 50 W but better a bit more) you may do this:
  1. Desolder L502.
  2. Apply ChipQuick low temp solder to the two pins of Q507.
  3. Take a bit of flux on the metal of Q507 opposite to the two pins.
  4. Take a blob of normal solder with your iron on this metal of Q507 and wait 5 or 8 (or 12) seconds or so until you could take Q507 away. Because of ChipQuick the heat coming through Q507 to the pins is enough to melt this solder.
  5. Remove all ChipQuick from the solder pads for the pins.
  6. Don't remove the solder from the pad for the body of Q507.
  7. Apply a bit flux on the solder pad for the body of Q507.
  8. Hold the new Q507 in place using tweezers and heat Q507 like in No. 3 and 4 until you feel Q507 is swimming on the solder.
  9. Remove the solder iron and hold Q507 in place until it's fixed.
  10. Solder the two pins.
  11. Solder L502.
73 Ludwig
 

Thank you, Ludwig. That does it. PA voltage now 0.3 instead of 10.9.
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73,
Steve, N2IC
 

Steve, good job.
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73 Ludwig

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