SE/30 suddenly no video

[jeauxlb]

Was powering along this afternoon, installing everything I'd need with my new network connectivity in the SE/30. I was serving a static website and went to check on the progress of my FTP upload, when suddenly I could connect to it no more.

I went over to it, and the screen was entirely blank, exactly the same way it looks when powered off. I powered down the machine and swapped the logic board with a known-working one. It booted without a problem.

So it appears that I have a video issue with my logic board. Searching these boards I've looked at Se/30 no video and checked the pinouts on J12 for continuity. It didn't make sense to check the voltages right now as that's a PSU thing — and this board presents the same issue on two recently-working PSUs.

The logic board has recently been through a clean and recap, and been working for the past few months since I got it. I recently installed an ethernet card and a 68040 accelerator (thank you Bolle) but that was working for 48 hours almost non-stop, without any such issue.

I'm not very familiar with the SE/30 video components, so any suggestions for where to start looking would be much appreciated. I do plan to check HSYNC and VSYNC from UI6 however do not have an oscilloscope at home so it might be a few days to organise that.

 

[jeauxlb]

I have also traced out A(0) to A(7) heading into UA8–UD8 chips. No continuity issues found.

 

[jeauxlb]

I started it up this afternoon after a thorough clear with IPA around the video area and letting it sit overnight without power. I at least got some activity on screen:



If this provides any direction for where I should look next would be very grateful to hear your thoughts. Many thanks.

 

[bibilit]

Looks like a usual behavior of a bad UE8 chip. 74LS166.

Probably replacing it with a new one will solve the issue

 

[imactheknife]

Looks like a usual behavior of a bad UE8 chip. 74LS166.

Probably replacing it with a new one will solve the issue

Or, remove it and clean pads / legs and reinstall. Sometimes i have had to remove the 3 ic’s around the whole area

 

[jeauxlb]

Thank you @bibilit and @imactheknife, I’ll focus my next efforts around cleaning/replacing UE8.

Probably replacing it with a new one will solve the issue

Will this part do the trick? https://www.mouser.com/productdetai...=sGAEpiMZZMtsbn1GaJysl8drSYt3ukOhxRl7aLOSxWU=

 

[jeauxlb]

Hi all, following up to say a big THANK YOU. I ordered the part linked above, and removed the old UE8. Once I soldered in the new part, it immediately worked and I have a functioning SE/30 again.

Super happy and very grateful. Thanks for the help to solve this issue.

 

[LaPorta]

I’m perplexed as to how video loss would lead to not being to connect over the network, however.

 

[jeauxlb]

I’m perplexed as to how video loss would lead to not being to connect over the network, however.

It's a great point and one I've been happy enough to ignore in my quest for a working display. I note that for reboots immediately after the display was failed, I was able to access its web server to verify it was fully booting.

I suspect it is a weird failure mode where a failed chip can impact other system components at the time of failure. But that's entirely a generalised guess.