The early Atari 5200s came with an unusual switchbox which supplied power to the 5200 down the same wire the 5200 uses to send the video signal to your TV. The power supply plugged into the switchbox. Unfortunately, these switchboxes seem to have gotten lost over the years and are difficult to come by. Newer 5200s (the one with only two controller ports) had the power supply jack on the console itself. Fortunately, it is not difficult to construct your own RF/power supply box for the 5200. There is one difference, though. The original 5200 switchbox would automatically switch from your TV antenna/cable to the 5200 when you turned the console on. With the RF/power box described below, you will need to use a standard game/TV switchbox to accomplish this function.
What do I need to build the RF/Power box?
The following parts are needed to construct the box. Where applicable, Radio Shack part numbers, and prices, have been provided. You may use another RCA jack in place of the F jack if you wish. I chose to use the F jack to avoid ever accidentally plugging the 5200 and TV cables in backwards, which would result in 11.5 volts DC going into your TV set, possibly damaging it.
RS# Part Price
-------- ---------------------------- -----
270-235 2"x2.75"x1.625" Aluminum Box $1.99
274-1563 Coaxial DC power jack $1.79
278-212 Cable TV type F jack (2 pack) $0.99 (optional, see above)
274-346 RCA type phono jack (4 pack) $2.49
272-131 0.01 uF Ceramic Disc capacitor (2 pack) $0.59
Small metal bolt (1" long, 3/8" diam, approx)
22 guage solid wire (14" or so)
Total $7.85 + local tax
How do I build it?
Drill holes in the aluminum box for each jack to match the diagram below. The box itself forms the common ground connection to all three jacks. To reduce signal loss and ensure the common ground, I recommend using chrome or gold plated type jacks.
F jack (to TV)
__
+-------------| |-------------+
| |__| |<--- Aluminum box
| | |
| \ 0.01uF | Solder the leads of the capacitor to
| \ _ Capacitor the center pins of the F jack and the
| \/@| | RCA jack. Make the choke by winding at
| \/ | least 10 turns of 22 guage solid,
| \ | insulated wire around a 3/8" (approx)
| Choke \ | diameter bolt. Wrap tape around the
| ---|/////|---\ | completed choke to prevent it from
| _L _L | unwinding. Strip the insulation off of
+------| |----------| |------+ each end of the choke leads. Solder the
|__| |__| leads of the choke to the center pins of
DC power jack RCA jack the DC power jack and the RCA jack.
(to pwr supply) (to 5200) Screw the box shut. You're done.
How does it work?
The capacitor transparently passes the video signal from the 5200 to the TV output jack, while at the same time preventing the DC power from the power supply jack from going into your TV. The choke (inductor) transparently passes the the 11.5 volt DC power to the 5200 via the RCA jack while at the same time preventing the video signal from escaping back down the power supply wire. The bolt around which the choke is wound helps to increase the choke's inductance to block more of the video signal from going back into the power supply than it otherwise would. The aluminum box itself helps keep the video signal confined to where it belongs to prevent possible interference and to ensure that as much of the signal as possible gets to your TV. For this reason, plastic boxes are not recommended.
Power supply info (if you don't have one).
The 5200 power supply is 11.5 volts DC @ 1.95 amps and has a standard type coaxial plug (center positive 5mm OD, 2.1mm ID). Or you could construct one from a transformer, 4 diodes, two capacitors, a resistor, a 3A adj. voltage regulator, heat sink, case, and cabling, or find a 12V 2A power supply and add a diode inline to drop the voltage by 0.5V, but that's another project!
Switchbox instructions by Bruce James Robert Linley, linley@netcom.com