SE/30 video issue that has ME stumped!

[techknight]

It's worth noting that although the Toshiba 74HC166D is a CMOS part, it appears to be TTL tolerant.  It worked fine as a replacement in my case.

Not in all cases. See below:

ISSUE RESOLVED!  Techknight, you may want to add this to your notes.

It appears that Texas Instruments SN74HC166DRG4 is NOT a valid replacement for the the 166 shift register @ UE8.  It causes the discussed artifacts.
I swapped it out again, but this time with a Toshiba 74HC166D, and the issue completely resolved!

Guys, I can finally put this thread to rest. Should be pinned because its something I overlooked in the beginning and this is one of those times when TTL vs CMOS is hyper critical. 

In some cases, I have used these parts interchangeably for years and never had an issue, but this is the one case where it became an issue. 

I removed the HC166 that was on the PCB from a previous attempted repair, and replaced it with the correct LS166 and the issue is now RESOLVED. It is fixed. Works perfect. So thanks for the idea, I thought I had already looked and checked for that beforehand, but guess not. haha

This is the one time where TTL vs CMOS had gotten me, and its super important information for others to know. 

So finally after all these years, I can bring this thread to a close. 

 

[trag]

This is the one time where TTL vs CMOS had gotten me, and its super important information for others to know. 

So finally after all these years, I can bring this thread to a close. 

Fun and informative narrative.  Thank you.

 

[techknight]

No problem! At least the issue is resolved. 

I can finally get this board back to its owner. 

 

[JohnnyLoquat]

Bumping this thread because I have a similar issues and would like another perspective. Most of what you guys are talking about here is over my head. I’m an amateur when it comes to electronics work but comfortable doing recaps.

I have 2 SE/30s.

First, both machines have had 99% IPA baths/scrubs, so there’s no cap goo sitting around visibly. They also both had all surface mount caps replaced.

1. The first SE/30 boots with sound after the recap, but suffers from the vertical jail bars just as described here by @NE555 and @error1. The lines are overtop the cursor. Based on this description, should I focus my attention on using a multimeter to test UE8 next?

2. My second SE/30 had the caps falling off when I got it, but no battery damage. It cleaned up ok. The usual corrosion around C7 which seems worse than the other machine. I never turned it on when I got it due to the original capacitors falling off, but it seems to be doing something very similar to what the previous owner described. See this video:


View attachment IMG_9253.MOV





If anyone could point me in the right direction on where to start with either of these I would be very appreciative.  Thank you!