Atari Football Graphic Problem

[troxel]

Game is showing to lines of garbage. The Xs and Os are at the bottom of the screen. Everything checked in test mode, and most voltages checked fine. I was getting +13 for the +25VAC, but the sound is working fine, so I wasn't worried about that measurement. The other voltages were right on.

I have replaced Big Blue with another and got the same problem. Reseated connectors and IC and still get the same problem.

Any ideas on where to look?

 

[troxel]

A bump for any ideas? Thanks.

 

[orion3311]

I fixed a simliar Baseball board where some of the characters stuck to one side and it had simliar garbage but on the edges. I believe it was one bad ram and one bad logic chip but I don't have my notes handy (nor would it be the same anyway).

I'm getting a Football board to learn a little bit about them.

 

[troxel]

Getting closer...piggybacked some of the RAMs and found a bad one. Replaced it and now have a new problem. The X's and O's move fine but "disappear" at certain lines and then reappear. It like there is a invisible line on the 34 yard-line and they show up on the 33rd and 35th.

I have piggybacked all RAMs, reseated all sockted ICs, and replaced the Motion
Object Generator RAM located at B6.

Here is the before and after picture, and tried to mark the invisible lines.

Any other ideas on what to check?

 

[troxel]

Another bump. Hoping someone can at least point me in the right direction to what part of the CPU to check.

Graphics only disappear for the X's and O's. The line appears to be in the same spot (about 1/4 of the way in) even if the screen scrolls.

 

[DarrenF]

Disclaimer: I don't have, nor have I ever had, an Atari Football...

But it looks like such a cool game, I decided to download the manual and take a look. I love Atari manuals. And the older the game, the better they were.

The video appears to be made up of 3 parts: the alpha/numerics (which appear fine on yours), the scrolling field (which also look good), and the motion objects (sprites, Xs Os and football) which seem to have the problem.

"These motion objects are generated by the same circutry found in the scrollfield generator (see Figure 3-15) ... This circutry is used for motion objects when 256H is low, and for scrollfield when 256H is high." Other area that may warrant interest is the video summing circuitry, including the "scrollgate" bits.

Time for a logic-probe party! I'd maybe start by looking at the inputs and outputs of J5, K5, J6, E6, D6, J8 & H8.

 

[troxel]

Trying to figure out my logic probe, but noticed something on E6 (74ls157). Pins 13 and 14 had no input, but pin 12 was high. Does this look wrong?

Update: Looking at the manual, it looks like those inputs weren't connected. Another items I observed is the regulator is getting very hot. I would imagine this isn't normal?