Macintosh SE/30 Revival: Stuck at White Screen with Chime

[Compgeke]

I've recently picked up my first SE/30 (well, a logic board) and I'm not feeling the love for them so far. It was recapped, but non-functioning when I got it. It'd turn on, and one of a few things would happen. It'd do nothing, it'd chime then death chime a few seconds later, it'd death chime right away and occasionally I'd get a solid white display with death chimes. I've tried with various ram combinations, varying from 1 to 64 megs of ram (sets of four) to no avail. Also cleaned the RAM and ROM SIMM slots with deoxit to no avail.

Step 1 was giving the board a very good cleaning, something it badly needed. Previous owner hadn't done a great job at the cleaning part. This changed nothing.

Step 2 was redo the recap with my own capacitors. This helped to make sure everything was the correct way around and all the solder joints were good - it was hard to tell with the previous recap job. This did not fix the problem either.

Step 3 was to give the board an even better wash. Now it's pretty much spotless - can't even see crud under ICs. This still did not help.

Step 4 was try a different ROM. With my IIfx ROM we're at the current state.

So, with the IIfx ROM swapped in, fully recapped and cleaned, it'll turn on, chime and give a solid white display with some raster lines in it. If I check the dead mac scrolls, it says it'd be an analog board problem, however said chassis works absolutely fine with an SE board, so I'm not inclined to go with that.

At this point, I'm inclined to believe the next step would be start ohming out traces. Before I get through beeping hell, I figured I'd see if anyone else has run into this issue and if they found a solution. I'm not in a big rush to start beeping out everything  . 

 

[Bolle]

Output on UE8 is stuck.

 

[Compgeke]

Perfect, UE8 is the right track. Desoldered it, did an extra cleaning under it to be safe. Resoldered in and it changed to "Digital Snow" as I'll call it, in 3 distinct columns.

I'll order a replacement 74*LS*166 and solder that in with my next parts order. Hopefully that'll get me somewhere else. Couldn't find one to salvage off anything kicking around!  

 

[techknight]

Dead Mac Scrolls isnt aging well at this point. Just an observation. 

 

[LaPorta]

I’d say Dead Mac Scrolls is good for your garden variety stuff, and adjustments. It wasn’t intended for “you haul out your 30-year old Mac with cap goo and see this error pattern” issues.

Ive had a similar “white snow in three columns” issue before. It always came down to some crud under a part somewhere that you didn’t know about that is shorting something. I’d look for the most likely area that crud would be (near where you cleaned it up) and look under those parts. On a regular SE once, it was a corroded via under the SCC that I couldn’t see, for example.

 

[techknight]

We almost need a Dead Mac Scrolls II. a recollection of all of our experiences and fixes for those issues.

But I digress. I think this logic board has a bad UE8 for sure, and potentially bad 74F253 RAM muxes.