Figuring traces based on physical board location instead of connected components

TrueNorthStrong

Well-known member
Hi folks,

To avoid burying the lede, this is yet another SE/30 simasimac repair post.

I've got one board that is just not cooperating with me, though at least I've narrowed down some areas I think are most suspect.

Current condition is a boot to jailbars, no sounds. RAM and ROM are known good, tested in another SE/30 I have successfully recapped. If needed I have yet another known good SE/30 as well to compare against or swap in components. No change either with RAM removed (but ROM installed) so the fault is very early in the boot process. As I understand it, video ROM related.

The majority of the board damage was under C9, and near the negative terminal of C8. Had some lifted pads on the three caps in this area, and the board underneath was clearly damaged. I also cleaned up the soldering joints on the UA8 - UG8 ICs on a recommendation. Some warranted investigation but check out. I haven't checked all the legs but I'm trying to avoid exhaustively checking connections until I've run out of spot checks to do. Moreover, while the caps in this area (C3 - C7) were definitely leaking, the board underneath was hardly damaged if at all.

I confirmed that the soldering work I've done for the caps themselves are good, but it's the traces underneath that I suspect are related to the boot issues I've got at the moment.

Two I was able to beep out and patch up, headed off to UJ11. I patched from via to via to bypass the damaged area.

But that's part of the issue. I can see traces that certainly seem suspect, but I'm having trouble finding what they're actually connecting to.

I'd imagine that I could refer to the SE/30 Reloaded board schematics, but I don't have the appropriate software to open that up and review it.

Is that the recommended way to investigate specific board traces, or does anyone have a recommended approach?
 

ymk

Well-known member
You can download a Gerber viewer here:


If the Reloaded project is done in KiCad, you're better off downloading that, since it also will link the board layout with schematics:

 

TrueNorthStrong

Well-known member
Thanks for the suggestions. Looks like I didn't read closely enough into the details on the SE/30 Reloaded board with is not a 1-to-1 redraw of the original tracing. Sure enough it's vastly different in the area I'm concerned with.
So, for now I'm back to square one of exhaustively checking all connections on the board.

Any suggestions of areas of focus based on the presenting symptoms? I checked out the video ROM connections which all seem fine from an inexperienced trace checker. Related question: if a trace runs to multiple locations, should all connections be checked?
 

TrueNorthStrong

Well-known member
Unless I’ve missed something, those schematics are the logical schematics. My original intention was to find the original, physical board schematics so I could find which traces are the ones run under capacitor C9 and check those first before diving in to the tedious work for checking everything.

I’ve got the redrawn logical schematics printed out and I’ve been slowly plugging away at some spot checks based on the current functionality. I was hoping to get lucky. Not yet!
 
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