DistantStar001 Posted May 23, 2019 Share Posted May 23, 2019 So I just got a new c64 board, ASSY NO. 250425, that starts up with a mostly blue screen on startup, with a few garbage characters on the left side of the screen. The Diagnostic cart runs and performs all tests, but I have no idea what the results are since all the characters are garbled. However, it passes the Dead Test with flying colors and clear text? So far, I have eliminated the RAM, all 3 ROMs, CPU, both CIAs, the PLA, the SID, the VIC II, the clock 8701 as suspects. The board is pictured without ICs, but the ones I installed are good. Any ideas? Quote Link to comment Share on other sites More sharing options...
DistantStar001 Posted May 25, 2019 Author Share Posted May 25, 2019 Figured it out! Replaced 2 MOS ICs, and discovered that I had a 74LS374 where a 74LS373 should have been. Quote Link to comment Share on other sites More sharing options...
DistantStar001 Posted May 25, 2019 Author Share Posted May 25, 2019 And then a RAM chip died. Quote Link to comment Share on other sites More sharing options...
DistantStar001 Posted May 30, 2019 Author Share Posted May 30, 2019 So like I said, replacing U26 made my computer boot normal for about a day, then it went to black. I opened it up, and the transistor at Q3 fell off. I replaced the transistor and ran a Dead Test and all I get is one flash on the screen indicating U12. So I replaced U12 and no change. Reading further in the Dead Test Manuel, I discovered that one flash could also mean either U9 or U21 as they're associated with data bits 1 and 0. I have replaced both chips, and still, all I get is one flash?? Any Ideas where this new fault is? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.