I've been having myself a good time installing a batari/longhorn engineer designed 7800 video board into my personal "keeper" 7800 unit.
I purchased it from "electronicsentimentalities," a member here who has taken batari/longhorn's open-source design and crafted some nice boards:
And, his instructions are quite easy, too:
The installation is done, and sound and video head on out the composite and S-video jacks as expected . . .
. . . but I'm getting those pesky, rolling diagonal lines that others have talked about in the past!
The diagonal rollers show up in both the composite AND the S-video outputs. It DOESN'T show up in 2600 mode, only 7800.
I have done my research, and tried multiple things in an attempt to solve the problem - -
- Detached the 4-pins that go to the RF modulator (the above picture shows them as attached; they are no longer)
- Removed the Q8 transistor (as was suggested here: http://www.made-by-b...101&t=842#p3415 )
- Removed the Q1 transistor (from the AtariAge 7800 FAQ: "In order to prevent the audio from interfering with the video signal, the mixing oscillator must be disabled on the main circuit board. On a 7800, remove the base lead of Q1. It is located near the RF modulator." [click on text to link to page]
This post cryptically offers some advice - -
"I disconnected the audio from the video in order clear up the diagonal lines. Where it is disconnected I added a cap to amplify the audio. Where did you get the audio signal?"
But I could not determine exactly what was meant . . . ! Maybe I already did that by removing some of the transistors
And, this post also offers some hope . . .
"I had to disconnect at R3 to remove all interference to the composite signal."
But again, I am not certain what is meant? I am going to have to go look for "R3" on the board after I post this!
Does anyone have some advice?
The picture is great - - nice and crisp, no shadows, but those diagonal rollers, especially on a dark background, are VERY noticeable!
Thanks SO much for any and all ideas!!
Edited by atari2atari, Tue Feb 28, 2012 11:07 PM.