SE/30 project

[petteri]

I just brought home an SE/30. It came with two motherboards and both are somewhat faulty. The disk drive works at least. At least other motherboard has some caps replaced with through hole caps and ugly solderings. I have to check the amount of memory and the ROM revision. There is no SCSI drive inside.



I have to do some research first regarding the repair options. My original idea was to do yet another RaspberryMac but let's see if I can revive this one.

 

[LaPorta]

I keep finding that this sort of thing occurs from cap goo under nearby chips causing shorts. Look by the chips near where the caps are for your likely suspects.

 

[petteri]

Yep, I think I need to build a CRT discharge strap, take it apart and clean up the board. Luckily I have plenty of IPA and other cleaners available at home.

 

[Crutch]

You don’t need to discharge the CRT to pull the motherboard.

 

[techknight]

its probably broken traces between ICs within the vicinity of UE8

 

[petteri]

The motherboard for the totally messed screen looks like this:

/monthly_2020_03/large.1545129564_spareboardclose.jpeg.04a6c7d9872d4984b8ea99965eabda04.jpeg/monthly_2020_03/large.1676485381_spareboard.jpeg.c19394816d73a7488adf145715508599.jpeg

I'll give it a wash first. Then I have a look at those caps.

 

[petteri]

Well, the wash with water and dishwasher and then good IPA rinse didn't make any difference for worse one of boards. Still totally messed up video.

 

[LaPorta]

Definitely just use IPA. If you use water you should let it dry for a day or more, it won’t all evaporate. The cap job looks ratty at best. Your best resource here is TechKnight, he has helped me with confounding issues on quite a few projects.

 

[davidg5678]

I think that this board can probably be repaired with a bit of work. I would recommend recapping the entire logic board from scratch, being sure to use solder flux and new SMD style capacitors. The solder joints underneath each existing through-hole capacitor look highly suspicious to me.

I keep finding that this sort of thing occurs from cap goo under nearby chips causing shorts.

I'd second this: Once you remove the old capacitors, you can clean the board again with Isopropyl Alcohol to remove the goo that they may have leaked in the general vicinity. If adding brand new capacitors to the board after this does not resolve your issue, it is very likely that leaked "cap goo" is part of the problem.

Good Luck!

 

[petteri]

Alright, I washed the "better board", too. It seems to have a recap job done with through hole caps but with a little bit nicer soldering. I did a lighter wash with IPA only. But after drying up I got only horizontal stripes. Based on the info online I decided to swap the RAM & ROM SIMMs around between boards and after couple swaps I found a working condition and the SE/30 boots up again. But I still get the square dotted screen as in the first post. Also, there hasn't been any startup chime (loudspeaker or headphones) on either board. 

I think my next step is to desolder the caps from the "worse board" and give it one more wash before re-recapping.

 

[petteri]

The "worse board" received de-capping now. Unfortunately, it turned out that C9 has lost its other pad at some point and now only a crater remains. I was going over them with flux and fresh 60/40. I have to find out where that pad should connect to so I can measure or jump wire it.

 /monthly_2020_03/large_C9.jpeg.a274e9b0bde8a3c5ad42f1d9fc322dcb.jpeg

Edit: J12-7 -C9 is gone. Any advices how to handle this one? I wouldn't like start drilling holes here. 

 

[LaPorta]

The tiny through-hole via right by the bottom left corner of C9 in your picture is where the cap connected to Pin 7, I just verified on my spare board. I'd run a wire from there to the end of the cap. If all else fails, solder the negative side of the cap to the back of the board directly to pin 7, and then run a wire from the positive side to any ground point...the cap terminates in the ground.

 

[petteri]

I checked all the capacitor pads with multimeter based on this: 



I found out C9- to J12 pin7 is not there, but C9- (or whatever solder is left in the crater) is actually shorting to the ground. I guess I should suck/wick that out?

 

[petteri]

I decided to ignore the old C9- pad and resoldered caps. For C9- to J12 pin7 I made a rather ugly jump as suggested by LaPorta. Now I get a startup chime, screen is perfect and it tries to boot up. But looks like the disk drive failed, it doesn't want to start reading the System from the disk anymore. It just spits it out after couple reads. I guess the drive's worm drive needs some cleaning and lubrication as it used to work couple days ago. 

I got the Welcome screen once, then it just shows happy mac and ejects the disk after a moment. For an unformatted disk I get the "disk with cross" icon.

 

[LaPorta]

Congratulations on getting it to at least start properly! Someone had really butchered that board before, and I am glad you didn't have more of an issue.

For the unformatted disk, that is normal to get the X, as the computer sees that it is not a System disk.

As for the other disk, sometimes when there is an inappropriate system version or some other issue with the disk itself, that can happen where the machine restarts right after the Happy Mac. Do you have another system disk to try? 

 

[petteri]

As for the other disk, sometimes when there is an inappropriate system version or some other issue with the disk itself, that can happen where the machine restarts right after the Happy Mac. Do you have another system disk to try? 

The same disk used to boot fine on the same machine couple days. After re-recapping it did load like in the screen shot above but then loading stopped. On the following attempts it just ejects the disk after the Happy Mac icon, like in this video I found:

.

 

[bibilit]

Dirty head or damaged disk.

The drive should be cleaned and serviced.

 

[LaPorta]

That too, indeed.

 

[petteri]

Rather embarrassing turn in the story. In the morning I stepped on something hard and that was C7. I had dropped it before soldering and somehow ignore the empty spot. Strange that the computer was able to work at all. Anyways, I soldered that in to place and cleaned disk drive. No change. I need to get a replacement System disk and try it again.

I wonder if I managed to cause any damage by running without C7. I guess the disk drive is at least semi operational as it is able to distinguish Mac formatted and blank disk.