Long time lurker; first post.
Attempting to repair a bunch of bad vias on a LC475 / Quadra 605 motherboard and running into some problems because I don't have a good board to check against or any decent wiring diagrams... Board was owned by another person and they attempted a recap. I bought the board off of them after examining it and not seeing any major damage. After some repairs, board now has 'sad mac chimes', but no video. I am looking at 3 vias on the motherboard and am hoping someone with a good motherboard can help me figure out what they should connect to...
All board damage is around U30 (343S0129-01) and confined close to C136/C137 and C149/C150
This particular via (marked by red arrow) goes through the back side of the board. I've drilled it out after testing it. There is some light around the via, but even the backside of the board doesn't have a connection to anything.
Looking at Bomarc's schematic for the color classic (supposedly similar design) I can see R40/R38 which match nicely to R64/R65 above. They beep (continuity) to Pin 22/23 of U30 and Pin 5/6 of U29 (341S0788) but I don't seem to have a connection to anything in the middle. Bomarc's schematics aren't the greatest, but it should apparently be connected to +5VDC. Orange arrow *appears* to be connected to the same internal plane, but I have -3.3VDC there (which seems odd, but may just be a red herring). Can someone confirm that +5VDC is the proper voltage between R64/R65?
Attempting to repair a bunch of bad vias on a LC475 / Quadra 605 motherboard and running into some problems because I don't have a good board to check against or any decent wiring diagrams... Board was owned by another person and they attempted a recap. I bought the board off of them after examining it and not seeing any major damage. After some repairs, board now has 'sad mac chimes', but no video. I am looking at 3 vias on the motherboard and am hoping someone with a good motherboard can help me figure out what they should connect to...
All board damage is around U30 (343S0129-01) and confined close to C136/C137 and C149/C150
This particular via (marked by red arrow) goes through the back side of the board. I've drilled it out after testing it. There is some light around the via, but even the backside of the board doesn't have a connection to anything.
Looking at Bomarc's schematic for the color classic (supposedly similar design) I can see R40/R38 which match nicely to R64/R65 above. They beep (continuity) to Pin 22/23 of U30 and Pin 5/6 of U29 (341S0788) but I don't seem to have a connection to anything in the middle. Bomarc's schematics aren't the greatest, but it should apparently be connected to +5VDC. Orange arrow *appears* to be connected to the same internal plane, but I have -3.3VDC there (which seems odd, but may just be a red herring). Can someone confirm that +5VDC is the proper voltage between R64/R65?