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SE/30 corrupt video but system works fine

aapl2c

Member
Hello!

I obtained a Macintosh SE/30 that was mostly working - it'd sometimes take a few tries to boot (completely corrupt screen or no video) and then when it would boot, no sound. So I replaced all the caps on the motherboard and gave it a good manual (careful) cleaning with isopropyl alcohol.

I re-installed the motherboard it now boots reliably, sound is working, and has good voltages. However it has horizontal corruption as you can see in the attached photos. The system works ok otherwise. 

It looks as if there's horizontal white bars drawn across the screen pushing the correct video up in that space. The mouse cursor does not redraw correctly as it's moved about on the screen, but menus drop down/disappear ok.

So far I've tried:

- different RAM

- re-seating all socketed chips and ROM SIMM

- making sure sockets are clean, including a blast of DeoxIT

I see from another thread where similar issues were found, though the corruption looked different, vertical in nature, and in some cases apparently the system did not work otherwise.

Before I go down the road from that thread, checking trace/via continuity, does this seem like anything else anyone has seen?

Thanks!

Photos attached showing the issue at boot, in the OS showing the About this Macintosh screen, the shutdown dialog, and a photo of the re-capped motherboard.

IMG_6238.jpeg

IMG_6251.jpeg

IMG_6254.jpeg

IMG_6258.jpeg

 

Bolle

Well-known member
Hmm, that’s a weird one.

Solder joints around UD8 and UE8 look fishy.

I would start with checking continuity around those two. I’d check the chips itself in an external tester too.

You probably won’t get around checking all traces in the video area though.

What puzzles me right now is the mouse pointer redraw thing. VRAM writes are not working correctly there for some reason. Makes me wonder if the PALs are working correctly.

 

aapl2c

Member
Fixed it, turns out pins 3 and 8 on UD8 weren't making contact with their pads.

I was able to re-solder pin 8 easy enough (it's ground) but no matter what I tried, pin 3 and it's pad wouldn't take the solder... I ended up using a small bodge wire to connect them. Pin 3 connects over to the video ROM.

Here's a photo of the ugly bodge wire and working display:

IMG_6265.jpeg

IMG_6266.jpeg

 

LaPorta

Well-known member
Nice job! I’ve tried various ways to make such things look nice. Sometimes it’s all you’ve got. My main workhorse FDHD cosmetically looks great, but also has a bunch of patching on the board. No one will see it or know it but you. You do the best you can.

 
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