Link to directions for repairing solder pad?

[dnelsonfl]

Hi,

Anybody have any good links for clear directions on repairing a solder pad for a chip? A 4000D I recently aquired had a leaking battery. The battery damaged the chip at U177. The chip removed cleanly except for three legs. Those had suffered some effects of corrosion (green legs) and the pads now appear brownish instead of silver. (See pictures here and here, as it's hard to describe what I'm looking at). Thankfully that's the extent of the damage: everything else around the battery appears to be alright.

-David

[Dr_Righteous]

This should be helpful... http://amiga.serveftp.net/hardware_repair.html

[vic20owner]

To me it looks like the pad is completely removed.  I would probably run some very thin wrapping wire from the actual pin on the chip to wherever that trace ends up connecting (next point solderable in the trace).  

vic20owner

[dnelsonfl]

@vic20owner,

Yeah, it does look that way now that I've found a magnifying glass. Do you think 30 guage wrapping wire would suffice? Radioshack carries it reasonably and is close by. And I can pick up the other supplies I'll need... except the replacement chip (74HCT174, SOIC).

Stateside, I've only found it at DigiKey so far (linky). Jameco and the others only had the 74HC174 in stock. It took me about an hour to find a site that would help me figure out what the difference is. the HCT is TTL-compatible. I'm not sure if the HC would work, though it is certainly cheaper. Better safe than sorry, I guess... it's going to cost me like $8 after shipping and handling fees to get two of these tiny little chips. {sigh}

In the end, is it better to have a working RTC clock and a few ugly wires on the motherboard, or no RTC and an authentic looking motherboard? I'd rather have it work. :inquisitive:

-David

[Castellen]

The HC174 will work fine, as will most of the other logic variants, LS, AC, etc.

It's easy enough to repair the damaged tracks and pads.
Since a number of the tracks for U177 run underneath the device, just get yourself a piece of thin wire, like one from a standard ribbon cable (like old floppy drive cable).
Bare the wire and use a single strand or "hair" to run under the device, joining one end of the wire onto an exposed track or via, then running the other end out to where the pad used to be.

If not running wires under the IC, you can buy a green coloured overcoat pen which is a special laquer which you "paint" onto exposed copper and solder joints.
Done right, you can barely tell a repair job has been done at all.

Once you're ready to fit the new SOIC, it'll sit nicely on top of the repair job, providing you've kept everything neat.  Just solder the pin of the IC to the end of the wire strand underneath.

Most of this is drawn here:
http://amiga.serveftp.net/images/ViaRepair.jpg

It's possible to do fairly complex repair jobs quickly and easily like this, most often you can't even see it's been done, as it sits under the IC.

If it helps, I've also written a SMD soldering guide for SOICs here:
http://amiga.serveftp.net/Replace_SOIC.html


I can also supply the new SMD parts ex stock, but by the time I sent them from NZ, it'd be about the same price anyway.


Anthony.