Jump to content
LaPorta

SE/30 Logic Board Resurrection

Recommended Posts

While awaiting the SCC chips for my other SE logic board project, I decided to resurrect an SE/30 motherboard that I have had in my possession for a very long time. This came out of my SE/30 probably about 19 years ago. It stopped working somehow (I am no longer sure what the issue was), and on my high school allowance budget, I got a replacement SE/30 board for probably all of $10 at the time on eBay (it was the socketed one, too boot)! I decided to leave this one on the shelf in my room, propped up, as a display piece. There it sat for a good 15 years until I cleaned out my room when my parents moved.

 

Fast-forward to now, and I looked it over. All surface caps had to go, of course. There was at least one bad trace that ran under C3 and C5 that I repaired. All in all, the board itself was fine otherwise. Green corrosion was scrubbed off with vinegar and a toothbrush. All caps were replaced with organic polymer models so they won't leak in the future. Insert original RAM and ROM SIMM, and, BAM, the thing actually started to gray screen, with pointer (and it moves: ADB mouse moves the pointer without issue. Startup sound via the speaker.

 

Unfortunately, that is all it does: gray with the pointer, no blinking floppy. Reading my Mac Classic & SE Pina book, it seems as this happens when the Mac has bad SCSI signals (likely via a bad SCSI chip). For all I know, this is what the issue was when I replaced it all those years ago, I simply cannot remember. I'm going to check all the SCSI chip traces in case that is what it is, although so far they all seem to be good. Mouser had replacements, so that's a good thing. Regrettably, I have never done hot air/surface mount soldering other than caps before....so I may have to buy a surface re-work station. Before getting the SCSI chips, any other suggestions as to what may be wrong?

 

As an aside, I used my copper foil tape to advantage fixing that trace. I coated the trace in solder, taped the coper tape over it, applied heat so that it would bond to the trace. Works perfectly. I then used liquid electric tape to coat and insulate it. I've included pictures of that as well, it really is a pretty visually appealing way to fix a straight trace.

 

First photo is of the board before repair. Second is of the trace repaired with the foil. Third is the liquid tape over the trace repair. Fourth is the repair with the caps over it. You can see it blends in very well, you might not even notice. Fifth and final is the board so far with new caps installed.

 

IMG_4487.thumb.JPG.7ad06bd3b4224e54d484a31a3c3d1d4d.JPG

IMG_4492.thumb.JPG.a4308789ab87ebf069244341f9fc0ccf.JPG

IMG_4497.thumb.JPG.2f10df0d6338011e40453f8d86d65618.JPG

IMG_4499.thumb.JPG.652f8462e7485b016a331448c4f215ec.JPG

IMG_4498.thumb.JPG.b65e92cb52907b5e672ec0637bad4c8e.JPG

Share this post


Link to post
Share on other sites

Perhaps I buried my real question too deep in there: does it seem like the SCSI chip is the most likely culprit? Should I order some and change it out, or check other things first?

Share this post


Link to post
Share on other sites

Having just read probably the same page in Pina you did, I think replacing the SCSI chip is the thing to try!  (My first thought was, just run an early version of the System Software that doesn’t know about SCSI ... but of course I immediately realized that’s not possible on an SE/30.)  I think it should be quite easy with a hot air station (though I have never had to do this myself).  Do check all the traces around the SCSI chip first though.  I had a problem with my SCSI chip due to cap goo leakage that was fixable by adding a jumper after verifying one of the traces was bad.  (Unlike you though, I did see a blinking ‘?’ before the fix.)

Share this post


Link to post
Share on other sites

I've been very carefully checking the traces. One looked rotten, but, surprisingly, was just fine. I'll re-check as well. As an aside, I am thinking of buying a bunch of these chips when I order. I have a feeling in the future they will be gone and irreplaceable, and it will be good for the community at large for someone to have at least a limited supply.

 

I don't as of yet have a hot air station. I've been looking for one that isn't $1,000 or some such, but I also don't want an absolute piece of crap, either. I also have read that you really need a nozzle for each specific chip to match it's size exactly. Any recommendations in that area?

Share this post


Link to post
Share on other sites

Well I'm no expert whatsoever and hopefully someone smarter will respond, but I can tell you what I have ...  I got this X-Tronic XTR-4040-XTS bundle for about $150 a while back.  I have limited space so wanted a single compact unit that did everything I needed.  It includes various size nozzles and I was able to use it to easily remove & replace a couple surface mount ICs in the past by quickly moving the nozzle back and forth around all the pins.  https://smile.amazon.com/gp/product/B003TC8EQS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

You could spend way more for a Hakko unit that's probably far superior in every way, but this worked fine for me.

Share this post


Link to post
Share on other sites

I know on the Portable if the SWIM is removed or bad, you get the same results. 

 

Either way, cap goo loves to eat the traces going into the SCSI IC so check that as well. 

Edited by techknight

Share this post


Link to post
Share on other sites

In my opinion the SCSI chip does not go bad, each time i have been suspecting the SCSI chip, it wasn't.

 

I agree with Techknight, probably a bad trace.

 

What about the one next to capacitor C10 ? (the trace slanted next to UJ 11) looks gone.

Share this post


Link to post
Share on other sites

Believe it or not, that one does test good (I'll need to insulate it).

 

I have taken to using the SWIM/SCSI schematic to test all traces:

 

https://museo.freaknet.org/gallery/apple/stuff/mac/andreas.kann/schemat.html

 

The question I have on those diagrams is this: Where do all of those traces on the leftmost diagram of this page go to/from?:

 

SE30_SCSI2.GIF

 

That's all that I need to figure out the traces. I am currently working on those between the two chips and the jacks, but I know it won't be complete without those traces on the left.

Share this post


Link to post
Share on other sites

LaPorta,

 

If you're still looking for a hot air station to remove old caps with — a few years ago I bought a generic Chinese one off eBay for $40 including shipping.  If you search "828D" you should get a few listings.  Not sure how much they're going for now, but mine has held up well over the years and been very helpful for SMD work.  I've done three Mac logic boards with it and am preparing to do a fourth.

 

Probably doesn't compare to a $1k+ model, but it has been more than adequate for my vintage Mac projects.

Edited by 68krazy

Share this post


Link to post
Share on other sites

That's not bad, especially if you say that it has worked for years. I just also want to make sure that it is compatible with the tips needed for the specific chips. Those damn nozzles seem to cost a fortune themselves.

Share this post


Link to post
Share on other sites
27 minutes ago, LaPorta said:

If anyone knows about the traces, I still need to know about that, too!

The numbers next to the ends of the traces show on which page of the schematics those signals appear again.

Lets take the chip select signal of the SCSI chip for instance:

 

/CS is on pin 17 of the IC. Apple calls this signal /SCSI.

Now if you open page 3 of the schematics you will see the /SCSI signal again. This time it is referring to page 6. You will find it right below the middle of the page on the left.

It is going to the GLUE at pin 24.

 

If there is more than one number next to a signal at the edge of a page it will appear on all the pages that are called.

 

Share this post


Link to post
Share on other sites
23 hours ago, LaPorta said:

Damn, that means i would have to trace it all over creation!

Yes, but thats how the schematic was laid out. 

 

Testing between the SCSI and SWIM is an absolute waste of time, because once you know the PCB like I do, they both connect to each other back to the same vias. You need to test all the way back to the GLU/CPU/ROM section. 

 

The other thing is, the ASC and SCC share alof of the same bus connections and traces, How does it sound when its powered on? is the chime clean? or does it sound kinda "dirty"? This is a big clue! 

Share this post


Link to post
Share on other sites

Sound is perfectly clear, no static or otherwise. I will need to find those other pages and print them. I know the SCC is the serial controller, what is the ASC? It appears I will be hunting down a few hours worth of traces...

 

Thanks for the tip on the SCSI/SWIM. Don't want to needlessly waste time.

Share this post


Link to post
Share on other sites

if the sound is clear, then we know all the address and data lines are getting to the ASC. So if there are any breaks on the SCSI/SWIM, they are going to be at the junction VIAs. So you should test from the SCSI/SWM back to the ASC, or GLU/CPU/ROM. 

 

The breaks typically occur right around the 3 capacitor block in front of the molex, there are no good pics of that area. 

Edited by techknight

Share this post


Link to post
Share on other sites

So, as far as I can tell per schematic, I checked every...single...SCSI chip...trace, and all appear to be intact. I cannot find a breakage anywhere, so I am pretty much back at the start. I am including a photo of the area with the three caps near the molex connector.

 

IMG_4507.thumb.JPG.c8e1ea74a0d13cdf4c620d4ea521c983.JPG

Share this post


Link to post
Share on other sites

Bolle I’m trying...it’s so tedious I can’t do much st a time. So far they all seem to be working well. I wonder if something else is wrong not involving traces. I may shelve this for a while; I’m going mad.

 

i also can’t find page 9 of the schematics online, and multiple VIA traces go there. Any ideas?

Share this post


Link to post
Share on other sites

I'll re-check, because unless the resolution is so poor that I can't amke things out properly, some of the traces off the page for the VIAs lists "9" as where they go.

 

EDIT: In fact, I just checked, and on page 4, sure enough, there are Pins from the VIAs that specify that they go to 9. Perhaps this means something else.

Edited by LaPorta

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×