Looking for some SE/30 repair direction

[mmaseda]

Hello,

I have a SE/30 that has recently developed a display problem. Before I go into full diagnostic and repair mode I thought I’d post a picture here and see if anyone can spot any obvious fault and fix. This logic board was recapped a few years ago and has been working just fine. When this fault propped up the first thing I did was replace the ram and romsimm but didn’t seem to help. As you can see the board boots up fully. Anyone got any ideas before I go any further?

Thanks in advance,
Manuel

 

[Callan]

I'd check the logic / traces above C7. If the board wasn't cleaned properly after the cap kit the leaked electrolyte continues to do damage. The video circuit is right above C7 and is prone to capacitor damage.

 

[ymk]

Looks like a problem in a video address line.

I'd start with the shotgun approach of cleaning up and reflowing the whole row of video muxes.

 

[croissantking]

Looks to me like one of the VRAM chips isn’t being written to correctly and is displaying uninitialized data.

 

[mmaseda]

Thanks for the responses. I’ll breakout the microscope and take a look this weekend.

Manuel

 

[mmaseda]

FIXED !! Before I broke out the microscope I decided to do a basic continuity check of the address and data lines using the schematic cheat sheet. Amazingly the second trace I checked A(1) was open at Video Mux UD8 pin 12. Resoldered the via and board is now working fine. Thanks everyone for your advice.

Manuel