SE/30 with No Video

[Garrett]

Hi all, I decided to document my latest project board - yup, another battery bombed SE/30. Now, some photos!

This is how I received it (yikes).

Here's what it looked like after a very thorough cleaning.

This is where I'm at now:

• Battery holder removed
• UD1 removed, cleaned, replaced
• RP4 removed, cleaned, replaced
• F258's removed, cleaned, and replaced
  • Had to run one bodge wire here to compensate for a missing pad
• Entire board recapped
• Five address lines restored with some ugly bodging (it's only temporary while I troubleshoot)

Unfortunately, none of what I have done so far has amounted in any sort of video output. I flip the power and hear the typical quite pop from the speaker, but no chime and no video. Voltages are all within spec, and I have toned out every connection to the infamous UE8 chip. I also made sure Hsync, Vsync, and Vidout from the Molex connector were making their way back to the ICs.

I'm stumped here! To add insult to injury, my SE/30 reloaded board has almost the exact same symptoms. No video, no chime. It's like there's a component required for boot that gets destroyed by the battery acid. Regardless, I'd appreciate any insight on where to look next! I should also mention that the behavior is the same with and without ROM or RAM installed. On my good board, no ROM and RAM will give me a simasimac pattern.

 

[AndyDiags]

Have you double checked the UE8 connections? This area just looks really bad.

I had an SE/30 that looked similar in this spot and gave me lots of trouble. Reflowing the UE8 was a real pain, I noticed if I ever slightly warped the board video would still disappear even after pulling the chip and cleaning under. I had to use a microscope to verify every single pin was making a really solid connection.

With this much damage, it may be a good candidate for a donor board and transfer components to a recreated PCB as additional issues may appear on this board within a couple years.

 

[Garrett]

UE8 is making good contact at all of its legs. I did measure continuity at the top of the leg nearest the chip in order to make sure the leg/pad contact was good as well. Here is what it looked like after the cleaning. There's still some flux on the board from the recap, but I don't think that's my issue.

Do these LS166 chips fail often? I think I have one or two new ones I could pop in, but I don't want to go through the hassle if they're generally reliable.

One thing I did notice, is that there's no activity on any of the VID 0:7 lines which I believe originate at the VRAM chips or MUX chips? On a working board, I read about 12kHz on each line at UE8. Can anyone confirm where these signals originate?

The only other thing I haven't done is swapping the video PALs. Maybe I'll try that later. I am not so worried about the ROM address lines at the moment, because I should have some activity on the screen even without ROM or RAM installed.

 

[Garrett]

Well, I ended up ordering enough SN74LS393DR, SN74F253D, and SN74LS166ANSR chips to replace all of the video MUXs. I also have a different set of video RAM I can try. That'll be a last resort though, as the current chips aren't socketed.