68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
SE/30 Recap follow-up questions
Posted by: ScutBoy on 2017-01-22 10:58:15
So, I completed my first SE/30 recap last weekend. Bad news, was the machine would not boot afterwards. No chime, no screen, thought the fan would start, and if plugged in, the HD would spin up.

Noticed a couple of things. First was that UE8 still had some gunk near it. Gave it a good second scrubbing, but that didn't help.

I had  had a problem getting the negative leg of C2 (the big axial cap) loose from the MB, and the backside of the MB got a bit chewed up. Cleaned up as best I could, but it looked like I might have scraped up enough to expose some other traces. Trying to resolder this joint didn't help.

With my imperfect schematic reading skills, I saw that C2 and C5 negative were both supposed to run to ground. So - I freed the negative leg of C2 and jumped with a wire to the negative of C5 (a tant which is right next door to the neg leg of C5).

With that, the machine came to life - bong, nice steady screen, etc.

However, while the sound is good and loud, there is a steady ticking coming from the speaker (about 2-3 per second), and  a little bit of grumbly static underneath everything. The static seems to get slightly softer/louder as I adjust the volume, but the ticking is same no matter what the volume is set at.

So - is it plausible that my sharing ground between these two might be causing these issues? I see that C2 and C5 are both involved with UB10 and UB11, which are the sound chips.

Is there a better place to bring the ground from C2?

I know that C6 is also referenced a lot with sound problems, but I checked it and it seems to be a solid solder job on the new cap. No other obvious goo around the other UE* chips.

Thanks for any advice!
Posted by: mraroid on 2017-01-22 16:01:07
Maybe yuou can post some photos?

mraroid
Posted by: ScutBoy on 2017-01-22 18:22:10
Maybe yuou can post some photos?

mraroid
And show my crappy soldering job to the world? 😉

Seriously, I have the machine buttoned back up for now. I can take some photos when I get the time to pull it apart again later this week.
Posted by: mraroid on 2017-01-23 16:18:56
My first soldering jobs looked OK but were cold solder joints.  Very bad.  It gets better.

mraroid
Posted by: ScutBoy on 2017-01-24 18:48:14
So - a happy ending!

From the schematics I found a common ground on the "same side" of the audio chips and jumped a wire there. For the curious, from the negative of C2 (axial) to the negative of C25 (teeny tiny) on the other side of the board. Ran the rework wire through a handy existing hole in the board.

Sound is back to normal!

ADB ports and floppy drive check out. I'll need to test the SCSI port and serial ports, but I'm not too concerned at this point, since the internal drive seems fine.

I'll take the lesson that errors are recoverable with a little time, research and patience. I feel much more confident about doing the next one! Thanks to mraroid for the encouragement 🙂

Posted by: Scott Squires on 2017-01-24 19:07:45
Good to hear you figured it out! Must rescue all the SE/30s! 🙂

1