Mac SE/30 not booting anymore after recapping

[mcamporelli]

Hi,

Recently I bought a Mac SE/30 which took a very long time to boot and had no sound. These problems where clearly indicating bad capacitors. Therefore, I decided to recap the logic board.

The capacitors I used:

• 10x 47µF 16V tantalum
  
• 1x 1µF 50V electrolytic
  
• 1x 220µF 25V axial electrolytic (low-ESR)
  
• 1x 470µF 25V axial electrolytic (low-ESR)
  

The board fortunately didn’t have any corrosion and was in pretty good shape. The battery was dead, so I replaced it with a new one. Before putting the machine back together, I double-checked the solder joints and polarity of the new caps.

After powering on, the screen stayed black and the Mac didn’t boot anymore. Also, a crackling sound could be heard from the speaker. I uploaded a video which shows the problems I’m having: https://youtu.be/rfnAuOl2XXU A photo of the recapped board can be found here: https://imgur.com/a/ibhYC After disassembling the Mac and cleaning the board thoroughly again, the crackling sound disappeared. But still no video and no chime.

Although I tried to work with great care (after reading dozens of "how to recap" manuals), I'm starting to think I damaged a component or even worse: the board itself. And due to my basic knowledge of electrical engineering, I have no clue how to start troubleshooting  :-(  

Any ideas what might cause these issues? Your help is greatly appreciated!

 

[IlikeTech]

Did you lift any pads?

 

[mcamporelli]

No, all pads where in good shape before I started to solder the replacement parts.

 

[CharlesT]

I would recommend a very thorough cleaning. When I had my SE/30 recapped the floppy drives no longer worked. So I washed the whole board in hot water with Simple Green followed by a complete wash and soak in 91% IPA, followed by a blow dry. Let it finish drying for another 24 hours, then fired it up and problem was gone. 

Charlie

 

[Jinnai]

I also had a board I thought was clean but it refused to boot, I washed it again and it started working fine. It was tough to clean without feeling like I'd break something off...

 

[Unknown_K]

Did you get the polarity correct? The black bar on Tants is Positive, the black bar on Aluminum caps is negative.

 

[aplmak]

I've seen power supplies and analogs die after a recap... strange but those should be attended to at some point.. why not now.. They are a pain in the *%^& to do.. But they should be done. If you have a working SE you could try it in that machine... 

 

[BadGoldEagle]

@Unknown_K, I had a closer look at his board and mcamporelli got the polarity right. So it must be something else...

Maybe my eyes are probably deceiving me but isn’t there a bad trace between C2 and C7? 

 

[mcamporelli]

Thanks for all your replies!

@aplmak Unfortunately I don't have an extra Mac. And I would like to keep the recapping of the analog board as a last resort

@BadGoldEagle I think you may be right! (you have perfect sight, which explains your username...) I took some extra photos which can be found here: https://photos.app.goo.gl/qVGhwba60TnrLfbK2 And indeed: the trace next to C2 seems to be damaged and soldered to the C2 capacitor pin. Apparently that one got too hot from the soldering iron, because the old C2 was pretty stuck. So I guess the next steps will be cleaning up the short-circuited connections, figuring out the start and endpoints of that trace and replacing it with a wire, right?

 

[techknight]

it looks like the trace that runs right by C2 is damaged as mentioned, and its solder bridged to the axial cap! That how you fry shit. 

 

[BadGoldEagle]

Thanks for the high res pics, now I can definitely see the damaged trace... Try fixing that one first to see if it comes back to life. 

If it doesn't then you could always double check a couple of other traces. Look for the ones with a slightly lighter shade of green (again, namely around C2). And the solder blob on the positive side of C13 could need a little rework... Finally, I would try to clean up a little more around UB11 (sony sound chip) and UD12 (small square chip also in that region), maybe something is creating an interference? 

Let's hope that it didn't fry anything...

 

[Bolle]

Yep, that one trace is broken and gets pulled to ground by the solder blob on the capacitor. Clean that up and repair that trace. It goes from GLU pin 50 to pin 5 on the Sony soundchip at UB10.

It carries /BRST (Bus Reset?). Pulling that one low is asking for trouble I guess

EDIT:

I can not seem to find the notes on how the startup sequence works but I seem to remember the soundchip should hold the reset line low until the clock signal is stable and then release reset to start up the system.

 

[Trash80toHP_Mini]

Interesting, I'll have to wash the DOA SE/30 board to see if it'll work. Polarity's been checked/good in my previous thread, thanks gang!