• Hello MLAers! We've re-enabled auto-approval for accounts. If you are still waiting on account approval, please check this thread for more information.

SE/30 Simasimac persists after recap

Riilu

6502
So, I got a SE/30 for free since it was in pretty bad condition, screen burn in, dead HDD, and horizontal bars and no startup chime, now I've never had to restore a mac like this, my Classic II has never given me any issues (and of which i have removed the clock battery to prevent leakage) 

So, i quickly learned these horizontal lines are due to leaky capacitors, so i took the computer apart and pulled everything out. The insides of the computer was not good, the battery had leaked a fair bit, even causing rust on the metal frame as well as the positive battery terminal. The parts around the battery seemed fairly fine except the solder on the pads looked a bit weird, but the Y1 Oscillator on the board had been hit the hardest by this and the entire component has white spots and the legs broke off during cleaning, I did repair the legs using the leg trimmings from the capacitors i used for replacing. So I removed all the caps, managed to not lift any traces, while i intended to remove them carefully with heat, they just came off extremly easily. I washed the board with white vinegar, and then proceeded to rins it, I let it dry for two days in front of the space heater which dried it off rapidly. Replacing the capacitors and fixing the Y1 Oscillator, i tried to power the mac back on, but nothing has changed, so i took the rom out, saw some corrosion on the contacs, cleaned with denaturated ethanol and tried again, no dice, cleaned withwhite vinegar and then more ethanol, still nothing. So it seems it's dead, or there's something i've missed, I intend to take off the battery holder entirely tomorrow and check the traces running under it, but if anyone here has any tips on how to revive this old computer, then please do tell.

 
There are broken traces in the address and data lines. You will have to check all connections between ROM, CPU and RAM/muxes.

It is a lot of work but can be done:





Pictures of your board would help to estimate damage.

 
Seems I cant edit the post anymore, but now it's 12 hours later and I removed the battery holder from the board, but I cant see anything resembling a broken or damaged trace, maybe I just need to wash it again? https://imgur.com/a/fO0G8

 
Those do look indeed good.

Can you take another closeup of the ROM SIMM and the ROM socket on the logicboard?

If those show corrosion as you said there might be some contacts that are not making a good connection.

 
I believe I found the culprit, unless there's any other reason why it is like so, so i decided to test the voltages on the board , going by the floppy ports, the +12v seemed unstable and there is no +5v, it's just completly dead, multimeter reads 0.00

So that's an analog board issue then, are there any other places to test the +5v ?

 
ROM SIMM and socket look good.

The legs on the RAM muxes at UJ3 and UJ4 look like they corroded a little bit. You might have to check those.

You can check the +5V on the harddrive power connector.

 
I get 5.6v and 12.3 on the HDD power cable,  and i took a look at UJ2, UJ3, and UJ4, there appears to be corrosion on the solder itself, but i cant see any damage to the joints, maybe i should reflow them with the iron just to be safe?

 
Well i tested the connections on the ROM SIMM to the board to rule that out, and there are no problems there, man this makes me feel really defeated, it seems almost everything has been tested by now,but i still get the simasima pattern on the screen and no startup chime so i guess it's probably reflow the muxes that's left to do since i cant find vias for half the pins on them, nor where to they connect to, but I will await any possible other suggestions. If there are any detailed board layouts to look at that would be very helpful in troubleshooting since this appears to be a a three layer board  and i don't know where the pins of the ROM SIMM connects to.

Would it be possible to test the ROM in a Classic II just to make sure the the silicon just hasn't gone ahead and died, or are they incompatible?

 
Last edited by a moderator:
So I vaguely recall seeing another thread or post about the reset and interrupt button being the issue, so i decided to test these and there seems to be something weird going on, when the button is released, there's actually continuity, setting the multimeter to resistance, makes it reads 770 ohm released. So maybe that's the issue? Any thoughts? 

Here's the resistance values i got from both buttons

Reset switch 770 ohm released, 1 ohm depressed
Interrupt switch 1642 ohm released, 1 ohm depressed

 
Those values seem normal.

I would start checking all connections between ROM SIMM, CPU and those RAM muxes.

No startup sound and checkerboard happen when the ROM can't be accessed. Even though the traces look ok there might be some (or even just one) dead vias somewhere.

The schematics for the SE/30 logicboard can be found online.

 
Good eyes right there... nothing you look for on the first view.

I was more after corroded contacts as those seem to happen quiet often from batteries that gas out.

There are indeed a few traces that need to be checked.

 
I did test all the connections from the vias on the ROM SIMM to the joints under the connector itself, got continuity on all of them. Dont think thats the issue. I tested the address bus to the muxes and found continuity, will do the data bus later

 
Last edited by a moderator:
ok you need to check the address and data bus from the physical connector as you did, but back to the PLCC chips, NOT the vias. Poor test. 

Simasimac with no chime, no boot means the CPU CANNOT read the ROM. Many reasons for that, but thats that. I have fixed at least 30 of these horrible things. lol. 

if the CPU cannot read the RAM, you will get the same thing, but you would have sound, slow chimes. 

 
Last edited by a moderator:
Back
Top