SE/30 with Vertical Pinstripes

[Byte Knight]

Hey guys,

I recently recapped a SE/30 board for sound issues and in the process got the dreaded vertical pinstripes (aka gangster pinstripes).  I've got good continuity chip to chip with vid (0) - vid (7), so I'm thinking that UE8 may be bad.  Is there a way to confirm that this chip is bad?  And is there anyone that could replace this chip for me?

Thanks in advance,

Todd

 

[Bolle]

If you get stripes UE8 is working fine.

The stripes are the default content of the VRAM chips at boot time. Seeing them means the VRAM data makes it to the screen (which is the job of UE8 - taking in parallel data from the VRAM and sending it out serialized)

Your machine is most likely having issues reading the ROM. Do you get any chimes when turning it on?

 

[Byte Knight]

If you get stripes UE8 is working fine.

The stripes are the default content of the VRAM chips at boot time. Seeing them means the VRAM data makes it to the screen (which is the job of UE8 - taking in parallel data from the VRAM and sending it out serialized)

Your machine is most likely having issues reading the ROM. Do you get any chimes when turning it on?

Just to be clear - these are the vertical single pixel lines that occur every 8 pixels (see attached picture).  The issue comes and goes.  Everything else is working fine, even the sound now!

 

[Bolle]

Ah...

Well then check connectivity on the address lines going to the video address muxes (UA8 to UD8)

One of them will be broken. It’s also possible one of the muxes itself has a stuck input or output but I’d start checking for connectivity.

 

[Bolle]

It could also be a stuck input on UE8.

But as said I would check the address lines first.

 

[bibilit]

I agree with Bolle, first thing first.

But also more information here, similar to your problem, with stripes coming and going :

 

[Byte Knight]

Ah...

Well then check connectivity on the address lines going to the video address muxes (UA8 to UD8)

One of them will be broken. It’s also possible one of the muxes itself has a stuck input or output but I’d start checking for connectivity.

Thanks for the help!  I've got good continuity between pins 14 of UA8-AD8 to pin 13 of UE6.

 

[Byte Knight]

Did some further testing tonight - got good continuity from the pad of pin 2 of UE8 (vid0) to UC7 but not from the pin itself.  Ran a wire from pin 2 of UE8 to pin 2 of UC7 and all is good now!  I suspect a leaking cap adjacent to UE8 was the cause...