From: "Mike Ranger" Subject: Tech:Williams joust fixed! Date: Monday, December 14, 1998 5:47 AM Hi all... Put the Pac's on the side burner (2 down, 2 to go) to get a joust set up and running for a friend... Symptoms: 1-3-3 error with a blue screen. Started attacking the blue screen first. First looked at 1A, and there was no clock input (6 MHZ). Looked at the output RAM's (4589's) and there was no input. Replaced the 7474 at 4D and am now getting the rug pattern. 1-3-3 replaced , 1-3-2, replaced, 1-2-3, replace and it boots! Wait....all the text is corrupt. Suspect the decoder at 3C. Check socket, put in known good one. Still corrupt text. Leading form there are a series of '153's on a whim, I swapped one, but to no avail. Stepped back for a few days, thinking about the problem. I know that the CPU can get data to memory, as it passes self test. Data coming out of memory goes to one of two banks of serial shift registers (flip screen or normal). I forced the screen to flip, therby moving the data to the second bank of these chips, but still corrupt text. I know that anything after that, if bad, will effect more than just text. Hmmm...Doesn't the set of blitter chips have direct access to RAM as well? Check out a few signals to find that there was a broken trace on a previous repair in the write enable circuitry at 4L. Patched up the trace and we be Flappin!!!!! Mike