Commodore 64 External Power Supply, Part No. 902503-02

I present here some information about my Commodore 64 power supply. This is the repairable type, as opposed to the solid epoxy "brick" type which, at best, you could salvage the transformer from by carefully chipping away at the epoxy.

It uses a 3052P, which is a +5 VDC, 2A voltage regulator. NTE 1934 is an equivalent part.

When repairing, I used a 3W, 30 ohm resistor instead of the original half-Watt. The original diodes were 1N5400 (50 V), but I used 1N5408 which can withstand much higher voltages (1 kV) (see 1N540X datasheet to compare).

Photos and Images
  • My version of the schematic in png format is here (148 kB).
  • Photos of the exterior top, side, and bottom of the power supply enclosure.
  • Photos of the inside from the top here and here.
  • Photos of the top of the circuit board (with the 3052P regulator removed) here and here.
  • Photo of the secondary side of the transformer here, including an annotated version explaining the terminals here. Hand-drawing of terminals here. Additional transformer view here.
  • Photo of the original 30 ohm 2%, 1/2W, resistor. Units of top scale of ruler are metric, showing resistor body is roughly 1 cm long. Diameter is 0.15".
  • Photo of the bottom of the circuit board.

P. David Buchan

December 22, 2016