On 12/07/2018 09:56 PM, Jeff Liebermann wrote:
On Mon, 3 Dec 2018 20:53:52 -0500, bitrex wrote:

Due to an unfortuante jab with the head of a screwdriver it looks like I
have at least one, possibly two broken traces on this GPU card, on the
traces running between the processor and VRAM. Result is corrupted
display output/won't switch into high-resolution modes. The ram is BGA
and the GPU likewise and

Common problem with motherboards and steel computer cases with sharp
edges.

under a small heat-sink so hard to test
continuity, plus the trace width is very small, looks like perhaps 4 mil:

Ummm... 4mil (0.004in) is roughly #38 AWG solid wire.
https://www.calmont.com/wp-content/uploads/calmont-eng-wire-gauge.pdf
Looking further down the chart, you should be able to find stranded
wire using something in 2 or 3 mil range.

https://www.dropbox.com/s/ig9h3vjze5omlie/2018-12-3%2018-11-20.jpg?dl=0

Nicely gouged.

Any suggestions for mending a break on a trace like this?

Yep. Dave Platt has the right idea. I'll add a few details.

Find some thin plated wire and tin it. Sometimes, I get fancy and
flatten the round wire but that's not really necessary. Carefully
scrape of the solder mask from over the PCB traces and tin those.
Liquid flux helps. Solder one end of the wire, lay the remaining wire
across the gap, solder the other end, and CAREFULLY cut off the excess
wire. Don't use a knife as you're likely to also cut the PCB trace.

Clean off the flux with alcohol, let dry, and test with an ohmmeter.
Then, test the PCB. If everything looks good, cover with a little
Krylon or other acrylic paint. If you're not sure about the fix, then
use some wax, which is easily removable.

As Ralph Mowery mentioned, a microscope is very helpful. I use this
in the office:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Olympus%20SZ30/slides/SZ30-01.html
and this at home:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Bausch%20and%20Lomb/index.html
I have 6 microscopes, not including parts scopes. Only 3 are suitable
for soldering and PCB inspection. I also have a CMOS camera that fits
in place of one eyepiece and which can be used for photos and display
on an LCD monitor.

Notice the use of a microscope, flux, and tinning. However, I
disagree with the use of an Xacto knife to cut the wire.
QUICK CIRCUIT TRACE REPAIR
https://www.youtube.com/watch?v=a5A61fIu0kk


Thanks, I managed to pull it off by scraping away the mask, then lot of
flux, tinning, and tiny strand of wire method. Patched up the third
trace in from the bottom and video card boots into Windows now and
checks out OK, runs shader tests etc. as it should.

At age 40 I still test about 20/20 in my right eye, the left was that
way too at one time but worse now, but was able to nail the positioning
with tweezers and a fine tipped iron freehand, pirate-style this time.

I should probably invest in a good microscope, never needed corrective
glasses so far in life but check back at 45.