A 5200jr Mod (WIP)

Blackbird · November 12, 2017

I purchased an Atari 5200, but I don't practically have enough space to display any 15x15" electronics in my house. I used to spend a long time reading how to make vintage video game consoles portable, so I figured it might be a good candidate to mod and stuff into a smaller package. This is loosely inspired by Kevtris' 5200jr project.

For my 5200 "Junior" console mod, these are the requirements I decided on:

No custom motherboard PCB (but yes to circuits that could be feasibly hand-wired, like on a protoboard)
No custom-made plastic case
Be repeatable with instructions
Look authentic to early 80's consoles
At the same time, support conveniences like AV ports, HDMI, or USB power supplies

Status

Right now this mod is still a work in progress, but here are my explorations and some in progress photos.

Case: To make a console that looked somewhat authentic, my best reference here was, of course, the 5100 prototype that exists. This one resembles a miniature 5200 in aesthetic! Unfortunately I couldn't find anything which matched this 5200-like look, but, I did do a survey of various Atari clones of the period to see what came close. In doing so, the Sears Super Arcade II stuck out for a few reasons:

It has four ports in the front, like a four port 5200
Its not a popular variant of the console, so I avoid the look of a 5200 stuffed into an obviously 2600 case...
But its common enough I can acquire a case easily...
And this variant came at the end of the 2600 lifecycle, and truly does look like a stepping stone to the 7800 design. A 5200 Jr. on the market could conceivably have had an updated, sleeker design as the 7800 were introduced.

So here is my 5200 circuit board fitted into the Sears Video Arcade II case, temporary packing tape and all:

PCB modification: Similar to miniaturizing a 2600 board, the first step was to cut off anything beyond the boundary of the RF square containing the CPU, GTIA, etc. (This handicaps the controller circuits, which I will need to address later.) Unfortunately the 5200 is still a massive PCB, so deeper cuts are necessary. Via the schematic, I worked out that the right side of the board holds mostly AV circuitry, which can easily be replaced and in fact would be unneeded with an AV mod. This leaves some stray controller circuitry, and the oscillator. Because the clock is essential, I dremeled an irregular shape of it off the board so it could wire it floating off the board.

I put together a very basic AV circuit that only produces luma. (Actually, I did this first to make sure the 5200 works, since I don't have the right equipment to hook up an RF box to my TV). This will be replaced by a better circuit later. The clock is wired adjacent to it, though I will probably mount it below the board ultimately:

It's a bit frankenstein at the moment, but it works!

What's next: Since the console boots, I believe I've worked out that the basic mod is viable. Next is fix the controller circuits, modify the case with 5200 branding, and modify the buttons to be functional:

Replace the AV mod with the UAV mod so I can visualize games in color (and ensure no RF components are causing interference)
Wire the AV and USB cables through the appropriate slot inside the console
Mount the oscillator underneath the board. (The bottom of the console has a drop space and much more room than on top)
Create a protoboard for mounting the controller circuitry
Recreate/fix the Port 1 and Port 2 circuitry
Build the Port 3 and Port 4 circuitry (since I adapted the original console from a 2-port console)
Wire the bottom four case buttons to be (On/Off, Start, Reset, Clear)
Dremel off the old console nameplate from my 5200 shell
Dremel off the standoffs from the top of the Sears shell (they don't allow the console to be shut properly, I'll need a replacement)
Mount together and play!
Figure out how to attach the nameplate to the new console, fix the lettering on the lower buttons, polish