No sound or video

[cbrown319]

I was playing my 7800 for like an hour, switched games and lost all sound and video. I'm getting power across the board. Thought it might be the rf, and started the av mod. Complete the mod and still no sound or video. When I ground the video cable to the board I get a flicker of white. Just seeing where I should start looking. Thanks.

 

Chuck

 

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[+Stephen Moss]

What exactly do you mean by no sound and video?

Do you mean your are getting static (snow/hiss) or a black screen and no hiss? With not much information to go on the former may suggest a problem with the input or output from the RF unit, the latter may suggest that the unit is being held in reset.

[cbrown319]

What exactly do you mean by no sound and video?

Do you mean your are getting static (snow/hiss) or a black screen and no hiss? With not much information to go on the former may suggest a problem with the input or output from the RF unit, the latter may suggest that the unit is being held in reset.

I'm getting a black screen. How would I isolate or disable to reset?

 

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[Atarifever]

Likely entirely unrelated, but I used to get the black screen with some homebrews on my first 7800. The oddest thing was that I could fix it by turning the game on, getting the black screen, then leaving it going for 5 or 10 minutes. Once the system (or maybe game) "warmed up" (that's how I think of it anyway), the games would work fine. No idea what the problem was or why it was only homebrews that did this. That system is currently dead (dead power button), so until it's fixed one day, I won't be able to see if it still happens.

Edited May 4, 2018 by Atarifever

[Shawn]

[Trebor]

 

 

 

 

 

I was playing my 7800 for like an hour, switched games and lost all sound and video. I'm getting power across the board.

If it has not been attempted already, try an Atari 2600 game. It's a relatively easy way to test if the problem is the Maria chip failing.

 

When Atari 2600 games play fine, despite Atari 7800 games having issues, then you know it is likely a problem with the Maria (7800 graphics) chip only. It is unlikely the problem, but worth the shot, and does eliminate a possible - regardless how probable - issue.

[+Stephen Moss]

I'm getting a black screen. How would I isolate or disable to reset?

 

Sent from my SM-G950U using Tapatalk

 

You will need a multi-meter, and a copy of the schematic. The reset is controlled by U10, when the output of the voltage regulator goes to 5V that puts 5V on pin 8 of U10 causing the flip-flop to set and pin 13 to go high (4-5V). When the 7800 is turned off pin 13 goes low (0V) holding the system in reset. Check this is operating as it should, if it is the reset signal may not be reaching all parts of the system it should so that would be the next check I would do.

 

Does this problem occur with both 2600 and 7800 games? That would indicate if the problem lies within the common parts of the system of those part specific to either 2600 or 7800 games as applicable.