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| Repair lifted pads on classic 2 |
Posted by: zachmayer on 2022-06-30 05:56:23
I’m working on recapping the logic board for a mac classic ii. I ordered a tantalum capacitor kit from console 5, and watched a lot of Branchus Creations videos to prepare.
There’s 17 capacitors, and I got all of them removed from the board. However, I lifted 6 pads while doing this, and now I need a plan to repair or replace the pads.
For 5 of these pads, they connect to a nearby via hole, so I plan to jump them with a thick wire anchored to the via hole, as in this video:
However, the 6th pad doesn’t connect to a via hole. It just connects to a very thin copper trace. How do I repair a pad like this? (See attached image, it’s the C15 capacitor).
I find myself wondering how important this capacitor is and if I can perhaps just skip it (probably not).
I also find myself wondering if I should spend $50-$80 on some silver epoxy on Amazon and just epoxy the sucker back on (though connecting the epoxy to the trace will be tricky).
Has anyone repaired a pad like this? It’s gonna be a little tricky and I need some encouragement to go after it lol. I’d appreciate any advice you have! I’m not super dexterous, but I’ve been able to solder the new capacitors on all right, so I’m looking for an easy repair.
Thank you! |
Posted by: macuserman on 2022-06-30 06:13:21
Got a multimeter with continuity? If so just take your probe and follow that trace back to wherever it goes, hopefully it runs to something that has a nice big pad, chip pin or another cap etc, then just run a bodge wire from there directly to the leg of your new cap. You can solder your bodge wire to the trace as well but it's tricker/more delicate so since it isn't a beauty contest I'd just hunt for the other end and run a nice new wire. |
Posted by: zachmayer on 2022-06-30 06:19:25
I don’t have a multimeter with continuity! Where can I buy one?
what’s a bodge wire? If I’m running a long wire l, how do I keep it attached to the circuit board? |
Posted by: Skate323k137 on 2022-06-30 06:24:09
You're in kinda a tight spot space wise there.
If your multimeter has OHM mode then it can functionally act as a continuity tester. 0 ohms = continuity.
The correct repair I suppose is consulting a schematic and seeing where that point leads.
My LBE (low budget engineer) self would lightly scrape the solder mask off that trace, tin it, and install the SMD cap slightly crooked. Don't be like me. |
Posted by: zachmayer on 2022-06-30 06:26:25
“Install it crooked” works for me lol.
will that tiny little trace be sufficient to anchor that side of the cap? |
Posted by: Skate323k137 on 2022-06-30 06:38:52
“Install it crooked” works for me lol.
will that tiny little trace be sufficient to anchor that side of the cap? If the other side is anchored firmly 1st.
Using a bodge wire would be similar, solder down the good pad, and then a wire from the other side of the smd cap to the correct point/component. Tack the lose wire here and there with hot glue if you need to. |
Posted by: zachmayer on 2022-06-30 06:49:50
Yeah the other side is pretty good so I should be able to anchor that.
I’ll give it a try! |
Posted by: zachmayer on 2022-06-30 08:15:05
What do you all think about silver epoxy? Has anyone ever used it before? It’s expensive: does it work? |
Posted by: Skate323k137 on 2022-06-30 08:21:44
I've never tried it.
For SMD stuff, the Chipquik solder paste is my best friend. Although in this case I might use leaded solder on the good pad. |
Posted by: zachmayer on 2022-06-30 09:16:40
Also, I have the 6 detached pads. I know the answer is probably “no,” but is there any way to reattach them? |
Posted by: zachmayer on 2022-06-30 14:34:30
“Just put it on crooked” worked surprisingly well.
I’ll test the connectivity when my multimeter comes in the mail and see if it’s actually connected but it seems like it worked! |
Posted by: Torbar on 2022-06-30 16:08:57
I can double check tonight, but I'm like 99% sure that pad goes to this pin (I'm recapping a Classic 2 and that pad happened to get lifted on this one as well) |
Posted by: Torbar on 2022-06-30 17:10:41
Just checked, yeah C15 gets to that pin, so if theres continuity you should be good |
Posted by: zachmayer on 2022-06-30 18:12:17
Thank you so much! How did you figure out that’s where it connects? |
Posted by: chiptripper on 2022-06-30 19:44:52
You can’t reattach pads. Or rather I don’t recommend it. I wouldn’t use silver epoxy either, personally. Bruce’s techniques are your best bet.
But there are replacement SMD pad kits. You place the new pad, glue it down using heat, expose a bit of copper on the trace, and bridge the two with some fine wire. Tricky soldering technique, but doable.
As an aside: my first recap was a Classic II, and I pulled 5 pads. It’s a tough board. After trying lots of methods since, I’ve landed on: gently twist off the can portion with needlenose pliers and (important part) firm downward pressure. Haven’t lost a pad since. |
Posted by: Torbar on 2022-06-30 20:36:28
Thank you so much! How did you figure out that’s where it connects?
I just kind of assumed it connected somewhere to that chip, since it didn't appear to exit from under the chip anywhere. On my board luckily I still had the pad attached, it was just lifted from the board, so I was able to use one probe on my meter on the pad and 1 probe to figure out which pin on the chip it went to. |
Posted by: imactheknife on 2022-06-30 20:39:26
Hey there, nice classic ii🙂 Hate to bombard your thread! I have a classic 2 i am working. I cant find a place on the negative side of c10 to check for continuity. Any ideas? I tried grounding it on scsi port. |
Posted by: imactheknife on 2022-06-30 20:40:16
Attached picture for reference |
Posted by: jajan547 on 2022-06-30 22:33:27
Attached picture for reference Probably connects to a via under the board |
Posted by: zachmayer on 2022-07-01 05:38:29
gently twist off the can portion with needlenose pliers and (important part) firm downward pressure. Haven’t lost a pad since. Thank you for the advice! I’ll do that next time! |
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