Debugging basic amp circuit

[Tex Gore]

Hey folks - I'm sure this is an easy one but I'm new to this and still learning.

• When I apply DC power to the board, D6 fries.
  This only happened after D4's legs got shorted together (it's possible they also shorted to D5 - explaining how is too embarassing but involves a croc clip soldering heatsink, the telephone, and an awful short-term memory)
  I replaced D6 - it still fries
  If I remove the IC 4558 - D6 still fries
  I've tested around the board for a short and I can't find one
  I've tested the PSU and it's fine

Could someone offer a hypothesis?

Many thanks

[tip142]

Check the polarity of the power supply,make one photo of your board,probably you made some mistakes.

[Dirk_Hendrik]

Not the cause of your problem but either D4 or D5 (the one with the highest fwd voltage) is not going to do anything in this circuit.

[deltafred]

What sort of diode are you using for D6? (Assuming you have the power supply connected correctly.)

If it is a zener then it will overheat if the voltage is greater than it's breakdown voltage because it is straight across the 9v supply.

If it is a normal diode (1N4001 etc) then it sounds like you have it the wrong way round.

Without seeing pictures we are only guessing of course.

Good points made by Dirk and tip142.