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Bad rectifier diode in SMPS?


jamesk

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I have a Apple IIc that has a internal power DC-DC SMPS that fails under load. I don't see any physical defects so I am checking the likely failed components. The power supply has a large TO220 diode labeled C80(large font)44(small font), (next line) diode symbol, (next line) 004. This diode may be out of production. I can't find a datasheet and the pcb is from '83.

 

My DMM shows a forward voltage of .16V with the diode removed from the board. I am assuming that this is a 2-4A rectifier diode that should have forward voltage around .5V. The diode should be replaced with a 4A diode. Does this sound right?

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