I have an early 800 that only shows B/W from the monitor jack. I have several other 800 boards and parts to swap out and test with. I have swapped out the power board, CPU, Memory, OS, and every socketed IC on the motherboard with known good working together parts. After every swap and test only B/W output. I put all the original parts on another motherboard, and i get color. SO there is something wrong with the main board itself. I can not see a visible damage.
For a while when I was swamping parts, I did not notice that the one of the 4 pin wire connections (J114) between the main board, and power board had come loose. The loose wire was the one closest to the front. I did a re-solder on it and still got the B/W output. Could that have damaged something on the main board while I swamping parts and applying power?
Just to be sure I swapped out parts again and still only get B/W. I even tried adjusting the red thing in the middle on the main board a 1/4 turn each way to see if that would change. nothing happened.
Suggestions on where to look for a fault?