SE/30 video issue, half simasimac pattern

[LeSpameur]

The board is clean and has been recapped. I already replaced all the SMD video chips (F253, LS166, and LS393), but no luck. The picture is from an SE/30 listed on eBay, which has the exact same issue. Any idea? To me, the video circuitry doesn’t seem to be fully initialized. I haven’t probed anything yet. It'll be fun. The sound is also glitched, but that’s another story (or maybe another broken trace).

 

[David Cook]

The picture is from an SE/30 listed on eBay

Does your screen also show part of the floppy disk? If so, good news! That means the CPU, ROM, and main RAM are working.

Here is a tutorial for fixing it:

Thread 'Example SE/30 Video Repair - UE8 LS166'

Apr 11, 2025

I recently bought a Macintosh SE/30 with missing pixels / bad video. I thought it would help others to walk through how I found the fault.

Below, we see an image a startup image with the "insert disk icon" in the middle and the cursor on the upper-left. The cursor follows the moving mouse. This is good news as it means the most of the computer is working. If you are looking on eBay for an old SE/30, seeing even a partially valid image on the screen can tell you a lot about the state of the motherboard.



Vertically, the image appears correct. However, only 1 out of every eight...

• David Cook
• Replies: 12
• Forum: Compact Mac

 

[LeSpameur]

Thanks. It’s most likely a broken trace between UE8 and UC6/7.

 

[LeSpameur]

Does your screen also show part of the floppy disk? If so, good news! That means the CPU, ROM, and main RAM are working.

Here is a tutorial for fixing it:

Thread 'Example SE/30 Video Repair - UE8 LS166'

Apr 11, 2025

I recently bought a Macintosh SE/30 with missing pixels / bad video. I thought it would help others to walk through how I found the fault.

Below, we see an image a startup image with the "insert disk icon" in the middle and the cursor on the upper-left. The cursor follows the moving mouse. This is good news as it means the most of the computer is working. If you are looking on eBay for an old SE/30, seeing even a partially valid image on the screen can tell you a lot about the state of the motherboard.



Vertically, the image appears correct. However, only 1 out of every eight...

• David Cook
• Replies: 12
• Forum: Compact Mac

I forgot to mention something ; when I remove the ROM, the Simasimac pattern is normal, no vertical lines !

 

[LeSpameur]

Fixed it! It was a broken via between UD8 and the video ROM on address line 0. It also fixed the sound issue

 

[David Cook]

Congratulations!!!

 

[LeSpameur]

Congratulations!!!

Thanks!! What a relief after all this time spent probing and checking traces…

 

[GreenBar0n]

Fixed it! It was a broken via between UD8 and the video ROM on address line 0. It also fixed the sound issue

Nice work! That's exactly what I'm seeing on mine too, missing pin 4 on UD8, A0 - but also pin 12, A1, a new F253 will be here Monday . Congrats!