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 from which, at best, you could salvage the transformer 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 (because I had them lying around) 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.
  • Photo of the inside from the top with everything in final position here.
  • Photo of the circuit board attached to the heat sink (with NTE 1934) here. Note how the circuit board fits into two slots on the heat sink.
  • 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. It's just resting on the heat sink here for display purposes.

P. David Buchan pdbuchan@yahoo.com

December 22, 2016