Help with Macintosh SE/30 (bright horizontal line after recapping the Logic board)

[Doctor69]

Hi everybody, I recentla bought a working se30. I just checked it was booting and then I recapped the Logic board. I used tantalum caps and used the 25v for C9 C10 and C11. I tested the board and it was working fine but after a few minutes of running Beyond Dark Castle the screen turned black and a horizontal Line appeared. The Mac is otherwise working but the video is not. I crossed checked the analog board and it’s fine (Also recapped this). Any help? I’m just a hobbist with little technical expertise. Thanks everybody
PS: i checked pin 5 of the floppy connector for the -12v potential and it’s zero

 

[s_pupp]

PS: i checked pin 5 of the floppy connector for the -12v potential and it’s zero

For the SE/30, you can’t check the -12V through the floppy port.

I cannot recall my source of info for that, but I read about it after building a floppy drive port voltmeter, and getting 0V on the -12V line on every booting SE/30 in my possession.

 

[Doctor69]

Yes I checked it there and it reads 0V

 

[obsolete]

Are your PAL chips socketed? Try reseating them and cleaning their contacts.

 

[chiptripper]

Check the back of analog board for cracked solder joints, particularly the four-pin connector that runs to the CRT, and reflow anything that looks suspect.

 

[Doctor69]

No they’re soldered

 

[cheesestraws]

PS: i checked pin 5 of the floppy connector for the -12v potential and it’s zero

I cannot recall my source of info for that, but I read about it after building a floppy drive port voltmeter, and getting 0V on the -12V line on every booting SE/30 in my possession.

Yes, this is true. You will get 0V on the "-12V" line on the floppy connector of an SE/30. This is normal.

Check the back of analog board for cracked solder joints, particularly the four-pin connector that runs to the CRT, and reflow anything that looks suspect.

I came to this thread to say this but @chiptripper beat me to it. This should be your next stop.

 

[Doctor69]

Check the back of analog board for cracked solder joints, particularly the four-pin connector that runs to the CRT, and reflow anything that looks suspect.

The analog board is ok.

 

[chiptripper]

If AB is functioning fine, then it’s likely a logic board issue resulting in vertical collapse. Could be a failed UF8 (counter). They often get the worst of the cap leakage. Or maybe a failed video PAL, but that’s far less likely IMO.