The Atari 7800 started out with the usual problem for a lot of older consoles: it only had RF output, which is awkward on newer TVs. I went ahead and installed a composite video mod so it could connect more easily, and before getting into that I also corrected a couple of points from the earlier 7800 history episode regarding GCC being paid and the circumstances of Jack Tramiel leaving Commodore.
If you don’t want to modify a 7800 at all, I showed a cheap alternative that still works with the stock RF connection. I used a small early LCD TV with a tuner input and an RCA-to-coax adapter, and that let me test both a 2600 cartridge and a native 7800 cartridge without changing the console. Those older transition-era TVs are handy because they usually have tuner, composite, S-Video, component, VGA, and HDMI all on one set.
The console itself worked before the mod, but it was dirty inside and still had the original plastic film on the front. Once I opened it up, there was a fair amount of dust and some corrosion around the RF shield area, so I removed the shielding and set it aside rather than keeping it in the machine. The board layout was clean and straightforward, and the mod only needed a small board, a few wires, and a handful of solder points.
For the actual installation, I clipped two resistors and one capacitor called for by the instructions, then desoldered and removed the RF modulator. I used solder wick on the four signal pins and the larger support tabs, with a little flux and a bit more heat to get the old solder moving. Once that was out, I wired the mod board to the former RF modulator connections for ground, 5V, and video, and then ran the audio connection to the appropriate point on the main board.
Instead of adding new jacks to the case, I reused the original RF opening and fed a composite/audio cable through it. The cable came from a JAKKS Pacific Atari unit, and I used a clip-on ferrite choke as strain relief so the cable couldn’t be pulled back through the hole. I mounted the mod board in the space where the RF modulator had been and added the remaining output wiring there.
Before final assembly, I cleaned the lower case with soapy water and did some spot cleaning on the PCB with isopropyl alcohol. While working around the board I found a loose capacitor lead and soldered it back into place. I also added a 10K resistor on the audio side to help balance the volume between standard game audio and POKEY-based sound from titles like Ballblazer.
The finished mod worked on the first test. Pac-Man and Ballblazer both came up cleanly over composite, the picture looked sharp, and the audio levels sounded even.
— Aaron
Links
- RCA to Coax adaptor
- 7800 Composite Mod
- 7800 Composite Mod Instructions
- Ferrite Chokes
- Music used by permission
Timestamps
00:00 – Intro
00:30 – Corrections
05:31 – Alternative To Modding
06:23 – Initial Tests
09:23 – Initial Condition
11:00 – Disassembly
14:00 – Inspection And Plan
15:43 – Removing Components
20:00 – Installing The Mod Board
28:00 – Cleaning The PCB