Rate my modwork - 7800 A/V no-cut mod.

tjsnhgaming · August 23, 2021

First time working on an Atari console. Installed a no-cut composite A/V output mod, with the POKEY resistor in-line. Let me know if you see anything really obvious that I screwed up - again, new to working on Atari systems.

+-^CrossBow^- · August 23, 2021

As I stated on FB. Since you removed the RF modulator, it would have been likely easier to not even use the audio section on the board. Just have to lift the north legs of R5 and R6. Attache them together and then solder on a 10µf cap to the center tab of the audio RCA jack. + of the cap from the resistors with the negative lead to the center tab of the RCA. That would essentially replicate the proper mixing between the TIA and external audio line (Pokey), to maintain the volume balance between them and also be compatible with all cartridges.

My other concern is that while this bracket is designed well, it wouldn't allow for the use of the S-video jacks that I use because it is too thick. I can tell this based on how little thread you have left on the RCA jacks. The s-video jacks I use for the UAVs only has about 2/3 of the thread that the RCAs do.. maybe even just a little over half. As a result it would really require a different type of 3D printed bracket.

Where you grabbed +5 and ground is also fine, but you could also have just soldered the ground wire to anywhere along the outer edge of the PCB or even soldered on a ring to bolt down between the nut/bolt as I assume the back side of that would be touching against the ground plane on the bottom of the PCB from the RF anchor holes in the board. +5 can be gotten from the expansion port section as well as from the top of that small ceramic cap just to the left of your bracket assembly. And of course the LARGE traces down the center of the main board are the main +5 and GND rails that feed everything in the system.

But it looks clean and I don't see any issues with the work other than my initial concern in regards to the audio if using a Dragon Fly cartridge with it. What other systems have you worked on since you stated you are new to Atari systems?

Shawn · August 23, 2021

Looks like clean work. I would have gone with the R5+R6 for the audio as Crossbow also mentioned but outside of that nitpicking it's a job very well done :thumbsup: