SE/30 Logicboard Video Issues

[davidg5678]

My SE/30 Logic Board has recently stopped booting and now shows garbled video on the screen. It has been recapped and is being tested with a functioning PSU and Analog board (My SE motherboard works fine inside this shell)

This board worked correctly for about a year after being recapped, but it now displays a pattern on the screen that looks different from simasimac. I reflowed the solder joints on all of the chips around UE8, but this did not fix anything. Is there a particular chip that controls video generation that may be faulty?

 

 

[davidg5678]

I have been attempting to fix this board without success. I remade several broken traces that went to the chips around UE8 with 30 gauge wire. I also noticed that many traces around C4 were missing solder mask and beginning to corrode. I removed some of the parts in this area to get a better look at the extent of the damage. The attached pictures show an overhead view of the logic board and a close up of the worst corner. (The reset switch, Sony chip, and C4 were removed by me after the computer was broken -I need to run new traces to C4 as I ripped both pads...)

Please let me know if you have any ideas about why this is not working. 

Thanks!

View attachment SE30 Corner.jpg

 

[dochilli]

Did the Mac chime? If not, there is a problem with the ROM. Perhaps a broken trace.

 

[davidg5678]

I have finished repairing the damaged components near the video circuit of this logic board and ran some wires in that area to replace broken traces; however, the machine still refuses to boot.

@dochilli may be on to something as there is no longer a boot chime when I turn the machine on. Curiously, the boot screen looks the same regardless of whether the ROM SIMM is installed or not. I cannot see any damaged traces in the area near the ROM, but I think it is part of the problem. Attached are some pictures of the logic board in its current state along with what the boot screens look like. (With and without the ROM installed, respectively)

 

[davidg5678]

View attachment IMG_20190619_101206.tiff

View attachment IMG_20190621_121836.tiff

View attachment MVIMG_20190619_200624.tiff

View attachment MVIMG_20190621_121929.tiff

 

[dochilli]

I would check every connection of the ROM. Take the schematics und search for broken traces. If you did not wash the board before recapping then there is left residue of the caps under some chips that could cause broken traces.

Did you check the voltages at the floppy port? 5 & 12 Volt? Was the analog board recapped?

 

[davidg5678]

While checking the voltages at the floppy port on the SE/30 board, I noticed that I was receiving 1.63 volts instead of 12 volts! This is definitely part of the problem. The 5 volt rail had a steady 4.93 volts. I do not think that this is a power supply issue, because as soon as I checked the same supply with my working Mac SE logic board, the voltages were correct. This machine has a recapped analog board and power supply. 

The board was washed before and after recapping, but I can still look for broken traces: Can you explain the process you go through when using the schematics? Also -how would I check places on the bottom of the board with the top? 

Thanks!

 

[dochilli]

I use a multimeter and check every pin of the ROM port for continuity. My multimeter has two long cables, so I can reach pins on the bottom and the top of the board.

But I think you should solve the 12Vproblem first.