Subject: Running the C64 on DC

From: [email-masked] (Jeff Hunsinger)
Date: 4 Apr 1995 13:31:50 GMT

The July 1990 issue of 73 Amateur Radio has an article on converting
the C64 and 1541 to run on DC power. I'll summarize the C64 portion:

DC Power Conversion for the C64

1. Locate component CR4 on the circuit board. Mark the positive hole on
   the board. Desolder and remove the component.

2. Connect the marked hole to +12V.

2. Desolder and remove VR1. Looking down at the component side of the
   board, locate the vacant right hand hole where VR1 used to be. Connect a wire 
   to the hole and run it to +12V.

3. Locate L5. It will probably be in one of two locations. On the older
   version, desolder the right hand leg and lift. On the newer version,
   desolder the top leg and lift.

4. Connect +5V to the empty L5 hole.

5. Locate the R37 and R100 pads. Use a continuity meter to find the pads
   that are connected. Desolder and lift these legs. You will insert a
   60 Hz clock here.

6. You could generate this clock using a variety of methods. Here's one:
                                +12V
        __________________________|
        |                         |
        | C1    R1          ______|_______
        |-)|-+-/\/\/-+-----|6     8       |
        |    |       \     |              |
        |   XTAL1    / R2  |    MM5369    |
        |    |       \     |              |
        |-)|-+-------+-----|5            1|---> 60 Hz (to R37 pad)
          C2               |      2       |
                            ---------------
                                  |
                                 GND

C1 = 30 pF
C2 = 3-15 pF (variable)
XTAL1 = 3.57 MHz crystal
R1 = 1k
R2 = 10M

It is suggested that you use a short length of shielded coax cable to
connect the 60 Hz output to the R37/R100 pad.

Also, it is suggested that you use a frequency counter to tune the above
circuit to exactly 60 Hz.

Jeff