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caver01

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  1. After a very nice clean and a good warm up in the oven I have a clean, dry logic board that still exhibits “Chains of Love”.
  2. One change was the fact that this system originally had 8mb of RAM, but over time, I have removed the SIMMs and ROM to clean the board, and most of my troubleshooting has been with only 4mb on board. One thing I did was add the other 4 sticks. It was the first thing I thought of that might be an issue, but re-seating, cleaning, re-arranging—nothing seems to make a difference. In total, the RAM is 8 sticks, two different versions, but all 1mb. I have kept similar ones together within each bank. As of now, the board is warming/drying after a thorough wash, but I do not have high hope
  3. I can see moving forward with troubleshooting audio. The video setback—I could address that too, right? One thing at a time. But this boot issue now has to be the priority now if I am to make any more progress. I think maybe I will give the entire board a good soapy soak, rinse and dry. I did it once early on during the re-cap, but I don’t think I did a very thorough job as I continued to find electrolyte. It cannot hurt at this point.
  4. I did check for that probing adjacent pins along each side. It did boot once after replacing the ASC.
  5. ok, so i have an update. It’s good news and bad, which is frustrating how the video keeps evolving. I was able to bridge the pad for pin 2 on the ASC to restore the trace no problem. It worked great, stayed nice and flat, and buzzed cleanly back to A(5). This was the spot highlighted in green below. I decided to put the ASC back on and it went ok but I could not resolve a bridge between pins 27 and 28 on the corner. Then I realized the bridge was a copper pad from pin 28 (highlighted in red below). I was able to get it off without much trouble, so pad 28 is a goner. Maybe it wont m
  6. New development for sound! With the ASC removed, I started buzzing the lines from UE10 to various other components. I definitely found a problem: Pin 2 does NOT connect to Address line A(5)! I think I can see the failure point with the chip removed. Looks like corrosion of the trace right as it leaves the pad extending under the chip—probably broken right there. If I zoom in on that trace, it exits the area between pins 34 and 35 and heads past C5 to via between C3 and C2. That via tests positive to A(5) so I think I am looking at a broken trace right at the pad for Pin2.
  7. Given that I am also troubleshooting sound issues, I have removed the ASC chip using de-soldering alloy. This, along with appropriate cleanup was much easier than I expected it to be and I would not hesitate to use the technique to replace other ICs (video muxer(s) perhaps? In any case, I printed page 7 of the schematics on tiled sheets of paper for reference and I will be doing continuity checks for the ASC. It will be a LOT easier to do that with the chip removed!
  8. Well, I got the hang of reading schematics really fast—nothing like just diving right in. I have now successfully buzzed ALL traces on page 5 (video) which includes UC6 UC7 UA8 UB8 UC8 UD8 UE6 UE7 UE8 UF8 UG6 UG7 UG8 UJ6 UK6, R16 R17 R18 R19 R23 and all address lines mentioned back to the CPU. I have not tested lines that lead off-page except for the address lines to the CPU. All continuity tests were good. Where does that leave me? Shorts under the ASC or other chips that may be harboring electrolyte? A bad chip? Without direct design knowledge, I am left to speculate, but it
  9. That via does look a bit dark. Thanks for the advice on more flux. That seems to be a consistent message everywhere in my research—flux flux flux! Haha. Ok, so the via tests ok through the board and to R12. Actually, all of the capacitor connections tested good following a nice diagram I found that lists all of their continuity check points—many being one end of a resistor on the negative side of The board. I do wish my soldering was a bit cleaner, but I am getting better! I guess a week or two has passed since the recap, so perhaps I need to retest and verify them, and maybe
  10. The focus/lighting makes this look worse than it really is. Here is an extreme closeup:
  11. There’s a shot of that area. I did have one trace pull up (watched it happen) alongside that through-hole which I fixed with a wire. You can see the green insulation. But video was working after that fix (and I had a nice tinned stretch to pickup that trace and connect it to the via above. Thanks for reading along! So far all of the address lines to CPU are testing good from UA8-UD8. Questions coming. . .
  12. Ahh looks like once verified I can pickup A(0-12) off the video ROM
  13. One question that may make things go faster: are there some convenient vias where I can pickup address lines on the top side of the logic board? holding probes on the 030 pins is a balancing act. Now that I write this, I suppose I still need to do this at least to one spot if only to verify connections from the CPU, but if someone has a chart/image to easily verify front to back that might help.
  14. Having printed an enlarged page from the Video section of the Apple schematics, I have started probing. Once you get the hang of it, I guess these drawings are not too hard to understand. One thing that threw me for a few minutes was the repeated references to the same ICs. It left me wondering “well which is it?” before I realized that they each feature mutually exclusive pins—so I concluded that this is an engineer’s technique to simplify the drawing by splitting the ICs in two in order to group similar function/logic making it easier read (and troubleshoot). Armed with an image
  15. OK! Thank you so much for taking the time with this, especially the image. I will try to match up what you are describing withe the schems and do some probing. i really appreciate the hand-holding and hope it pays off with another rescued SE/30. I am also feeling better about my decision to get the desoldering alloy so I can do a better job of cleanup around and under the ASC. More to come, I am sure, but this answers a lot.
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