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So I'm fairly sure I have continuity to every pin on the CLUT now, excepting the bottom-right-most-but-one (see photo). Does anyone know if/what this is supposed to connect to? Thanks

Yup, here they are: The bodged lines are DQ5, DQ4, DQ26 and DQ27 (I believe). I do now have some very fine enamel wire so I could try to repair the traces in-situ, this approach with the vias was just easier for me at my current skill level. :) I think I've check out most of the CLUT now...

Yes; I’m suspicious about the VRAM<->CLUT<->MEMCjr signals. I think I’ve ruled out most of the VRAM SIMM signals (two I need to double check) so I’m going to focus on the CLUT linkage next. How sensitive is the memory bus, on these boards, to trace length? I’m starting to wonder if my bodge...

Not yet - I'm hoping some will arrive in the next few days. RAM data and address lines all seem to check out - from the on-board RAM to the SIMM. I'm going through the VRAM lines now (and learning a bit about how the VRAM setup works in the process).

Well, after an examination with a USB microscope I found that there was a tiny break in the A4 line on pin 14 of U18 - and a discontinuity between the northern DRAM chip's A4 and the southern - funnily enough it is in the same rough latitude as the other broken traces. A solder bridge and a...

Unfortunately I've got the chimes of death back after trying a RAM re-flow :( I'll see if I can find anything I've obviously damaged - unless it is the RAM chips themselves I've cooked.

That’s an idea. Do you mean the SIMMs? The on-board RAM or both? And what works best? Hot air? +flux?

Do you want photos of the screen? :) I've been (having a go at) identifying the chips to see if there are any likely broken traces between them. I'm using the board, the developer notes and the internet as my points of reference :) U26 should be CLUT/DAC (code-named Antelope), should have...

Thanks for the suggestion. I've done another thorough clean of the contacts (DeoxIT D5) for the VRAM and the board edge connector. Wiggling doesn't change anything on the screen for me. Though it does appear that the purple screen occasionally returns (instead of the more common grey screen) but...

Okay, after putting a through-hole 4.7k resistor to R109 I now get a grey screen - mostly fairly consistently. I've verified the connections of the video signals (by examining the CC logic board + schematics) to U26 which, I am assuming, is the CLUT/DAC as per the 575 developer notes. I've...

Thanks for the link! Though I think I need to find 33Mhz parts? My assumption was that XC68LC040RC258 was speed binned for 25Mhz? Guilty; yes, it is in a CC (analog board recapped - suspect caps only - and PPT7 calibrated for functional voltages). I've already moved R116 to R109 and checked...

Brief update: I have run 4 bodge wires from vias next to the broken traces to the pins on the CPU socket that they seemed to need continuity with. Tada: No more sad mac chimes! Thanks for the pointers and encouragement. The system sounds like it is booting (hard drive activity and an error tone...

Thanks for the pointers. The traces seem very small and close together for bridging with enamel wire or old capacitor legs but nothing ventured nothing gained! I'll grab some of the 40AWG stuff and see how I get on.

Long story short: I acquired a 575 logic board 'untested'. On testing it gave the boot chime followed very shortly by the death chimes. The board itself looked clean enough but I went ahead with a re-cap but this resulted in no improvement. After a wipe around with IPA, I can now see some...

Thanks; I looked up the SE speaker and saw that it was 63Ω/0.25w - which is actually what I'm looking for. The ink was smudged on my broken part so had me fruitlessly searching for a 68Ω. :)

Did you find a speaker? I'm looking for a replacement 0.25w / 68 Ohm to finish a Classic analog board repair; I don't seem to be able to find much out on t'internet