Simasimac SE/30 Diagnosis

[dcr]

I selected my guinea pig SE/30 to use as my first recapping test subject.  Upon opening it up and removing the logic board, I discovered it has already been recapped.  After examining it for any obvious problems, I reconnected the logic board, made sure the connections were good, reassembled the case and fired it up.

The results were the same as my last attempt to boot it: simasimac screen, no boot chime and no indication of accessing the floppy drive.

Where do I begin to look for the problem?  To my untrained eye, the board appears clean.  There was one wire on the bottom of the board that seemed to me like it might have been to repair a problematic trace.  Otherwise, it seemed okay.  RAM and ROM appear seated properly.  There is no hard drive and it seems to make no attempt to try the floppy drive at boot.  They appear to have kept the original battery from 1989 which is curious.

There is a PDS card to allow for it to use a VGA monitor.  I did not try to boot the SE/30 with the card removed; I'm going to try that but it seems doubtful to me that that could be the problem.

Thanks!

 

[Bolle]

Chances are it has not been properly cleaned when the recap was done so cap goo still had enough time to do its thing.

Possibly bad traces or UE8 went out in this case.

Taking a picture of the board might help so we could check for any obvious damage.

 

[dcr]

Here is a shot of the undercarriage.  I need to retake the picture of the top side.

 

[dcr]

Here's a photo of the top side.

 

[Bolle]

Are you sure it was already recapped?

Those caps look a lot like the original caps usually found on early socketed SE/30 boards like yours.

Axials are also still the original ones.

 

[dcr]

I don't know for sure.  I'll take it apart again this weekend and have another look.  I can't get good close-ups with my camera but it looked to me like the soldering around some of the capacitors wasn't original.  Maybe someone redid the connections rather than a recap.

If it's not been recapped, that makes troubleshooting a bit easier.  I just need to return to Plan A and recap it.

 

[techknight]

Those are DEFINITELY the original caps. 

RECAP the board. 

 

[dcr]

I washed the board, recapped and cleaned the board again.

I put the board back in the machine and powered it up.  On the plus side, nothing exploded and no smoking components.  The SE/30 now has a boot chime.  It also spit out a floppy disk I didn't know was in the drive.  It does attempt to load from a floppy (seems a bit slow to access it but maybe it's looking for the nonexistent hard drive?).  But there's no change with the screen; still has the simasimac screen.

Where do I go from here?  I'm guessing maybe a damaged trace or a bad soldering job somewhere, but are there any particular caps I should pay particular attention to?

Thanks!

 

[techknight]

Need a picture of the screen now that its attempting to work. 

Simasimac is highly subjective. 

 

[olePigeon]

Believe it or not, the screen pattern can give you clues as to what else may be wrong.  As tecknight suggested, a picture of the screen would be useful.

 

[dcr]

Here's what the screen looks like:

 

[techknight]

Appears the bus can write one of the RAM ICs, but not the other. Because you have a block of 8 bits of good data, but a block of 8 bits of bad data. 

I cant see any icons though so I dont know what state this is at. whether its sitting at a blinking floppy, maybe before that point? or is it even booted? no context here. 

 

[dcr]

That's how the screen looks throughout startup.  No icons appear.

 

[techknight]

ok. Hmmmm.... Wonder if there is an open trace between the GLU and video circuits. Especially if your getting a chime on the original ROM. 

 

[dcr]

I moved the RAM around to see if it made a difference.  It didn't.

ok. Hmmmm.... Wonder if there is an open trace between the GLU and video circuits. Especially if your getting a chime on the original ROM. 

Where do I need to examine the traces to try to hunt it down?

What does the component at Q3 do?  It looks sorta iffy to me.

 

[Bolle]

Appears the bus can write one of the RAM ICs, but not the other.

Would it even chime if that was the case?

Even though they look good in the pictures I would check UE8 and it's neighbours.

All data going into the video system passes through them.

Also make sure the socketed PALs are seated correctly and make good contact.

 

[dcr]

Even though they look good in the pictures I would check UE8 and it's neighbours.

Will do.

Also make sure the socketed PALs are seated correctly and make good contact.

I've examined them previously and they seemed to be seated properly but I'll double-check when I check around UE8.

Thanks!

 

[SE30_Neal]

I’m no expert but those definitely look like the original caps to me, technight recapped mine a year or so ago and they look completely different now. UE8 comes up alot as a problem. My screen did the same when I tried to install a rominator 2 and 128mb memory simms. Was fine and booted fine once i put the original stuff back in

neal

 

[dcr]

Also make sure the socketed PALs are seated correctly and make good contact.

All looked good but one did push in a little further when I pressed on them as a double-check.  They are all securely seated now and appear to have good contact.

I can't see anything wrong around UE8.  The soldering connections seem less shiny than its neighbors, but the traces appear intact and the solder does not appear loose.

When booting, I do now see a partial blinking floppy icon so I imagine the component I was able to push in further was a culprit there.

Still have the same screen appearance, except now for the partial floppy displaying.