Mac SE/30 general crashes (Bus error, Address Error, etc) recap done years ago.

[PastelNightmare]

Hello all! Just want to see if some more experienced people have some ideas of where to look or experience with any of this.

So, I have a Mac SE/30 which sat for a bit, I changed the PRAM battery, and now the computer doesn't work. I recapped the board in 2016, so I know it's been awhile. But, I examined my work from being inexperienced. There was some mess that needed to be cleaned, but I cleaned and touched up the board. It has 20mb of RAM in it currently, but any RAM configuration will cause issues. Below is the list of issues

1. The internal SCSI drive cannot be seen anymore. I hear it trying to be accessed, but only for a brief moment before it returns to the question mark screen looking for an OS.
2. An external device such as a BlueSCSI will have a happy mac for just a moment, then back to the ? screen, no matter what image or SD card I use,
3. I *can* boot into System 6.0.8 on a floppy disk. The internal drive still isn't seen, but the external one, if available, can be. Any further issues will assume I've booted into 6.0.8 on floppy disk
   1. Any attempt to write to external SCSI will fail. Write error.
   2. Any attempt to run a program from any source, disk, floppy disk, external.....crashes the system immediately. Except for small programs like the control panel or calculator.I can also successfully format a disk, both floppy and external SCSI.
   3. When crashing, the errors are all over the place. "Bus Error" "Address Error" "Coprocessor Not Installed" "Illegal Instruction" are the main ones I see. External SCSI attached generally causes bus and address errors. Without it, I get illegal instruction or coprocessor not installed for most things.
4. Maybe important: When I last ran the system 6 months ago, it did this until it just....started working normally again.

I have tried a few things, basically all amounting to no change. I've cleaned the motherboard, redid all the recap work I did years ago. I read something about reflowing the SCSI chip under similar circumstances, so I tried that. Visual inspection shows no broken traces, but I know you can't go by sight alone. The PSU was bad, so I had converted it to run on an ATX supply for testing, again years ago. Preliminary meter checks show all rails are where they need to be.

Basically, what I'd like to know is if anyone has any idea where I might look next for errors, traces, corrosion....etc. Or any diagnostics I can do. There is always of course the slight worry that I'd made the BlueSCSI wrong and it nuked the SCSI controller chip, but...being that it can see it and read from it, I'm not sure about that. Just don't want to lose one of my favorite machines!

Thanks!

 

[falen6]

i have just recently got back to playing with my macs

last month got a CC , the other day i took down an LCIII

on both machines i have found problems with rot/corrosion from vias and chip legs/pad connection.

Im starting to think about long term corrosion , how we clean the boards , are we doing it properly

I used to just wash the boards with toothbrush and hand soap , slowly and carefully , at every stage of the recap

then i heard about soaking the board in vinegar for a while , to kill any more acid , so i started doing that as well

then i heard about a third step , soaking the board in baking soda solution to nutralize any remaining acids / alkelines so
i started doing that also

If the electrolite corrosion starts 'soaking/ eating' through the solder , is there a chance that our efforts to stop the corrosion
is only working on the outer skin of the solder , leaving the electrolite under the surface untouched , eating away ?

should we soak the boards for a few days to give it a chance ?

its just that I have never had problems with vias in the past

these machines are getting older and older , with more and more time more problems are sure to arise

hopefully its just your bluescsi setup

 

[Boctor]

Did you wash, not just swap but totally immerse the board, when doing the initial recap? With mine, someone didn't, and it wicked corrosion and died years later.

 

[PastelNightmare]

Did you wash, not just swap but totally immerse the board, when doing the initial recap? With mine, someone didn't, and it wicked corrosion and died years later.

I did now, but not then. Too little too late I'm guessing. After I'm done with some personal life stuff, I do plan on just full on probing traces all around the caps, getting a better scope, etc.

 

[Boctor]

Hopefully if anything did get eaten through, it didn't wick into the blind vias or the internal traces. I had one recapped by someone else that clearly still had electrolyte hiding in it, and threw my hands up and went with the nuclear option.

If you know the history of your board, being the one who worked on it, you might have a better time with doing this the scientific way like you describe.