Started with hardware, which provides valuable basis for understanding computers!
I just completed a task on a Mac Pro 3,1, early 2008, A1186; I installed a pair of SSDs in the optical bay. This required running a pair of SATA cables from the motherboard to the optical bay, which in turn required removing the front fan assembly.
On this model, I didn’t have to do anything with the RAM cage. I removed the screw that fastens the fan assembly to the motherboard, and I removed the CPU cover (fastened with magnets — just pull and it comes off), Removing the CPU cover reveals another screw right at the corner between the heat sink and the fan assembly. After both screws are removed, the fan assembly comes off easily (it didn’t stick after I removed the screw).
According to comments, the next model Mac Pro has the cables already run to the optical bay. The question arises: does that model still have an IDE optical drive, or would we have to sacrifice the optical if we want to use both SATA cables in the optical bay?
After getting the correct instructions, I found that the CAIG pen is very hard to squeeze, resulting in unsteady, heavy line. Any pen should probably be shaken with an engraver of similar tool, especially if it’s getting old (Chemtronics claims a freshness date — look for one!). My first repair was successful, allowing me to test for other breaks. No need to use the rubber cups; pressing on the top membrane with a finger will contact the bottom membrane.
Breaks were very hard to see; used Ohmmeter to find lands that should be connected. Also hard to remove insulation without removing trace as well (no green paint on top). Maybe need to scratch fine line along trace with X-Acto knife to get through to conductor, without going to the side?
Next break is on top membrane; much harder to test or stabilize while drying. About ready to persuade wife to settle for used or generic replacement. :-P
You mentioned that conductive pens are a bit pricey in Canada. I found a CAIG Circuitwriter Conductive Pen on the peg at MicroCenter @$19.99. Price tag covered instructions. Once I was ready to try it, I downloaded instructions, first for the Chemtronics CircuitWorks Conductive Pen (5 minutes dry tack-free, conductive in 30 minutes). Realized my attempt wasn’t tack-free, so I looked further and found the instructions from the package online. Allow 24 hours to dry, cure with 40W bulb @6” 4 hours. Not the same! Also noticed the store UPC covers a Radio Shack UPC. If this has a shelf life of up to 2 years before purchase, how fresh is it?
Just now I tried to find the item online at MicroCenter in order to give this information and the only ink they advertise is Bare Conductive Electronic Paint — $11.99. Much better price, and shouldn’t be much more for you.
Please note that keycaps come off easily with a straight pull. Fingertips work well, but I would like to see suggestions of some other tool that might keep some people’s fingertips from excessive wear. Patience is important!
On my keyboard, the first screws on the outside are hex head, not cross head. I don’t have an Allen wrench that small, but I was able to find a Torx T5 wrench that would fit inside the Allen head. Thinking about using my BluFixx liquid plastic kit to make a real Allen wrench head for it, but this is working for now.
Note the author’s comment about possibly having to scrape off the insulation on a lead before applying conductive ink. Same advice should make a difference on your foil test.
Broken leads or dirt accumulation are the most likely reasons for this keyboard to fail. Other failures (decoder chip, USB interface) would show much more drastic symptoms than a few lost keys.
I think the pen should work. Note what the author said about possibly needing to scrape the insulation off a lead before connecting. Try that and the foil should give a positive indication.