Mac SE: Post-Maxell repair Attempts

[BadGoldEagle]

Hi folks

I bought a non-working SE last week and sadly, the Maxell bomb had already gone off.

NOT FOR FAINT-HEARTED

Spoiler

Already fixed the chassis with some white vinegar. Looks great. Might give it another bath just for good measure (there are still a couple of rust stains left).

I don't have too much time to work on the SE at the moment. (We have exams every 3 months or so at my university. I know, I always say that, but it's true! Unfortunately... But next week-end I'll have more time on my hands.)

Initially the display was filled with the checkerboard pattern.

So, I pulled the ROMs out, tested them on a known good unit. They work fine.

Then I bathed the "dead" board in some really hot soapy water for at least 2 hours. I used a toothbrush to clean the parts around the battery compartment. 

Here's how it looks right now:

    

 
 
I can't seem to make it look any better. Any advices? I already tried isopropyl alcohol.
Anyway, it now displays the Simasi-Mac pattern. Yes, the exact same Simasi-Mac pattern as found on the SE/30. No chime, no activity.
Now, I know there are two missing caps (big axial one near the battery terminal and a small tantalum? one near the speaker cable) so it wasn't supposed to boot anyway. The traces look good though.

Do you think I should replace those two caps, remove & clean the sorry-looking chips and then add new fresh solder to all the joints near the crash site? Or is this board too far gone?

Edit: All the damaged chips are as follows:

2x 115-0002 serial filters

2x 26LS32 (RS-422 Interface)

1x SCC chip.

Technically, a Mac SE boot without serial right?

 

[techknight]

The acid crap and corrosion still left behind are shorting things. You DO need to remove those ICs and either replace them, or clean in between the pins VERY well... Then and only then you can start trace chasing. 

Also there are crusty vias near C9 and R7 which I bet are toast once you scrape all that away. There is also a FAT trace which probably contains a power bus or even a ground bus right near the 26LS32 which I know for a fact has been eaten away at the via. 

When in doubt, use a flashlight on the opposite side and if you can see light through an annular ring where copper is supposed to be, its toast. You will see via to trace breaks this way. 

 

[BadGoldEagle]

Also there are crusty vias near C9 and R7 which I bet are toast once you scrape all that away. There is also a FAT trace which probably contains a power bus or even a ground bus right near the 26LS32 which I know for a fact has been eaten away at the via. 

Just after posting this I inspected the traces with a flashlight. That trace you're referring to is definitely toast. About 1mm of copper is gone. It's the only one I think.

Should be fixable with one big ol' jumper wire, right? 

Some more pictures:





Will definitely pull those chips and clean them properly. But an SE should work without any of the serial chips working, right? (IF every single trace near them are good)

Did some more testing: I get the Simasi-Mac pattern with 4mb installed (without jumper). Checkerboard with any other good config. If I try 1meg with no jumper (wrong config), then it acts just as if there was no LB installed.

 

[techknight]

Theres more than 1 trace bad. I can physically see it. 

Anyways, Even if the machine would work without the serial chips, your overlooking the fact that the acid/corrosion is shorting out all the pins! 

And then theres the corroded bourns filter. 

Your problem is definitely in that area. 

 

[BadGoldEagle]

Will buy the desoldering braid today. I don't have all the equipment to solder everything back in once I'm done with the chip cleaning thing. Will get it soon enough though.

I think at least one of the two bourns is gone. According to Uni, the DALE MDP1603-470G is a suitable replacement. Apple even used it on some SE/30s and he confirms they're working as they should on any of the compacts (including SE), despite having less legs than the Apple part. 

Now, I will perform tests before getting through the trouble of getting a new filter but if anyone was wondering how to get a replacement Apple bourns filter, the DALE is the way to go apparently. It's a little bit difficult to get hold of one but the Apple part is near unobtainable these days.

The Dales are SOOO cheap it's almost unreal. http://www.ebay.com/itm/52pcs-Dale-47-Ohm-Dual-In-Line-DIP-16-Resistor-Network-MDP1603-470G-470-470G-/112009716057?hash=item1a144ca159:g:byIAAOSwUuFWxu32

52 pcs for $2!!

 

[techknight]

It will run without them in the machine. 

If you use solder wick to remove those in one peice, you will be there until the end of time. 

My suggestion is get sharp small sidecuts and clip them out of there. It will run without them for testing purposes, and it will be easier to remove the pins and then clean out the holes for the new ones when they come in. 

 

[BadGoldEagle]

Got it. I bought the braid anyway because I'll need to put the SCC and the 26LS32s back after i've cleaned them. I won't need it for the bourns filter though. I'll break this guy's legs. 

 

[techknight]

Yea speaking of braid, I had to order up a new Hakko desoldering tool. my trusty old 808 got dropped and busted apart so it was time for another one 

May the 808 rest in piece. 

 

[BadGoldEagle]

I'm still trying to revive this thing. 

Bibilit helped me removing one of the bourns filters and it wasn't easy because of all the rust and oxydation... 

Afterwards, I got some of the corrosion off with another vinegar bath and some more scrubbing.

Some traces are bad (that's a given) but that's not my main concern right now. Some VIAs are completely rusted away and since this is a 4 layer board, I wonder if I'll be able to save it at all...

Basically, as I'm writing this, the "hole" is still filled with rust/metal. But what if corrosion expanded beyond the VIA? That's a game over innit? 

 

[olePigeon]

I may have a spare SE board you can have for the cost of shipping.

 

[BadGoldEagle]

Thanks ole, I'll consider it. But i'd like to save one if possible. Unfortunately Apple don't make new ones...

 

[360alaska]

It can be done but it really takes some doing, when I do this I start by sanding the board with 600 grit sandpaper until I can see copper, Next clean the areas with isopropyl achohol, next check continuity, next tin all of the bare copper with solder.

 

[360alaska]

Here is a Mac classic logic board I fixed using my repair method as listed above, I wasn't completely done with the job at this point but you get the idea:



Keep in mind when your trying to solder that the corrosion will inhibit the transfer of heat, it would really help to have some rosin paste and a 60w iron.

 

[BadGoldEagle]

Thanks for the pic alaska!   That will definitely help. Now I know how much I have to sand the board.

Will give it a go and will report back.

 

[BadGoldEagle]

Wow, can't believe it's almost been two years since I touched this thing. 

Anyway, good news! It's now 80% functional. The other 20% aren't crucial for now but I'll definitely have to come back and finish it later (perhaps in another two years?). What are those 20% you may ask? Serial. But the important stuff, SCSI, floppy, sound, ADB etc all work.



In order to get the sound back, I added another wire (the red one) to bypass C10. Not great but since that's only for audio, that's fine enough. Plus I will remove it once I get a replacement cap. It's temporary otherwise I would have made the wire shorter... It was a just a quick and dirty fix. Another capacitor (C13) was replaced as the Maxell obliterated the old one (I didn't even find its remains!).

I believe that all the bad traces are fixed. Several pads are still bad (I didn't bother fixing them because I focused on getting it to work and didn't clean up the pads where the serial filter used to be. By the way, do you have a Digikey part number for one of those?)

The chassis (the one on the LB) is still bad, and I can't desolder it. I'll give the hot air gun a go but I doubt I'll ever get it off. 



That's about it for today. I'm really happy!

Edit: Found a replacement Bourns filter. 4120R-601-250/201

 

[LaPorta]

Where did you find the filter? Is it the full 20 pin, or the 16? I could only find 16s, but my understanding was they will still work.

 

[BadGoldEagle]

The 4120R is (as the name suggests) a 20 pin package. I still haven't placed my order but I think I'll get it from farnell.

I've cleaned up the board and removed the rust on the chassis with a nail file. Looks quite good now. With the filter and a replacement battery holder you won't really be able to tell the damage (until you flip the board over that is...)

 

[LaPorta]

One thing that I really would love for you guys to try is EvapoRust: for the chassis, submerging it into that would get rid of the rust overnight, no scrubbing involved. It's great stuff,

 

[BadGoldEagle]

I did have to scrub a little with the vinegar and there are still a couple rough spots. One thing I’m not too happy about though is the looks of the undamaged parts after the treatment: they look very shiny and not very original anymore. What kind of results are you getting with that product?