Repairing Lifted Pads and Traces

[Mac128]

So I have a few dead 128K logicboards which were at one time upgraded to 512K. Meaning, the RAM has all been upgraded and they were fitted with Mini-Mux boards at location E3. Somewhere along the way, somebody pulled all the mini-mux boards in a real hurry (who knows why) and sort of made a mess of the pads and traces.

Since this is all part of my experiment to run these boards fitted with 256 RAM chips, as 128K boards, all I need to do is repair the area at E3. My initial thought is all I need to do is to re-fill the holes with solder as on a stock board and it will take care of making the contacts between the pads and any inner layers they may have been attached to. Does this make any sense? Or do I need to do more?

Also, the trace between pin 1 & 2 has been cut on these boards. Is the only thing I need to do is solder across the cut to restore?

 

[Unknown_K]

Solder is an OK bridge in area that does not flex at all. For anything else you need that fine flexible wire used in board reworks.

 

[MidnightCommando]

You may find that the wires used to wind small transformers / motor stators / TV tube yokes may work - it's enamelled magnet wire, and it has good insulation, high conductivity, and is easy to handle.

 

[Osgeld]

30 guage wire wrap wire is an option, same as above except instead of sanding off painted insulation you very carefully strip off krypton plastic insulation

It is what is typically seen on board jumpers

and since it is so thin it is possible to jam completely though a via, solder and clip, although results may vary

 

[CJ_Miller]

I have some experience with reworking boards. What I found with enameled wire is that it is - for me, at least - very difficult to tell whether or not I got the insulation off of a given area. Also it tangles very easily. I always suspected that it was shorting somewhere and got rid of it. IMO 30 gauge wire-wrap is ideal. It is narrow enough, the insulation (or lack of) is visible, stronger and just far easier to work with. I bought my Falcon030 damaged and redid some trashed traces with excellent results.

And of course if there are lifted pads, good luck filling them if. The solder will not reliably bond to anything. I recommend gently scraping the board mask coating away from the end of the traces and jumpering them directly with fine wire.

When part removal seems rushed and clumsy, it is usually either because someone did not have the patience to adequately heat and remove all of the solder, or the PCB holes were too small for the parts so they were jammed in. De-soldering is far more difficult than soldering.

 

[JDW]

I recommend gently scraping the board mask coating away from the end of the traces and jumpering them directly with fine wire.

That's what I do. It's easy and works well.

 

[Mac128]

When you say jumpering the pads with fine wire, do you mean recreating the loops and soldering to the trace?

I'm a bit confused about the pads though, from what I've read about this problem, they may connect to internal layers within the holes. In which case, how do you know? This is what I meant about filling the holes with solder (as they were originally) to make all the connections with the inner layers. Any clarification of how this works would be appreciated.

I'll take some pictures of this when I get the new iPhone in June and can take some decent pictures.