The manual I linked to earlier is for a different version of the board.
This copy has the correct layout information for your Atari type B board.
I've taken a closer look at the PCB and noticed the first edge connector pin (where it says A) is a bit crispy. Too much power going in? Can this affect the graphic sprites?
On page 4, upper left of the
schematic package, you can see that pin A is a 5v return line on J20/P20. (Jack 20/Plug 20)
The crispyness appears to be a sign of too much current flow and/or a poor (higher than normal resistance) connection.
A higher resistance connection will convert more power to heat, that speeds corrosion, that increases resistance, that converts more power to heat, . . . until it ends up like this or worse.
To verify if you have a poor connection at pin A instead of just an
ugly-looking but functional repair, you could use a multimeter to test the resistance between the top leg of R132 (slightly down and left from pin A in your pic) and P7 pin 1. (where the other end of the wire connects to the "Regulator Audio II" board)
As always, make sure no power is applied when measuring resistance -- unless you
want an excuse to buy a new meter.
A reading of less than 2 ohms should be good enough.
A higher resistance connection needs to be fixed by someone who can properly repair/replace the crispy trace on the PCB.
- Anyone who can do the trace repair can also chase down what is causing your missing sprites.
- You may also need to replace Pin A in the P20 connector if it was damaged/corroded by the heat.
Scott