I've personally done the sense mod to my ARII because I didn't want to replace the PCB connector right now (it's pretty loose), and I don't want the ARII blowing itself up if the thing works loose again.
Just an FYI......if your connector pins have lost their tension....You will burn up the motherboards "fingers" (regardless of sense mod, or not).
This is why I HATE the sense mod. IT WILL NOT FIX A SHOT CONNECTOR. This is an urban myth, perpetuated by internet mis-information. The sense mod IS NOT a fix at all. It's a band-aid.
Here's the hard facts.....when the pins inside an Atari edge connector lose their tension several things will happen: the two "sense" resistors on the A/R II board will burn up (on an A/R I board, it will be diodes)....sometimes only one will burn if caught in time. Next, you can burn up the motherboard's "fingers". This is happening because the edge connector has lost it's "spring tension", maybe the motherboard's fingers are oxidized......basically, where the edge connector and the motherboard connect, this connection is no longer "solid". This is the problem, and THIS needs to be addressed. So, what happens if you do the sense mod and do not address the actual problem? Well, let's examine what you just did. By doing the sense mod, you just jumpered the sense circuit to 5VDC. So, the A/R board is now using an additional path to send 5VDC to the motherboard.....seems like a GOOD idea, right? Well, in theory it is....but there's a fatal flaw in this theory. YOU DIDN'T REPLACE THE EDGE CONNECTOR'S PINS. We already know the edge connector's connection point is compromised. If it wasn't, you wouldn't have had the sense resistors burn. So, what are the consequences of what you just did. Since you didn't replace the edge connector's pins, they are still a weak point. They are still going to generate heat. So, instead of burning up one or two 1¢ resistors.....you're going to burn up your motherboards edge connector's fingers. This will take a bit longer, since the sense mod spreads the 5VDC line out over a few more wires.....but the nature of how the sense circuit works, the connection point of these (additional wires) has already been comprimised.
If your sense circuit is fine, and you're doing the sense mod as "preventative maintenance".......keep this in mind.....the sense resistors are the weakest point in the link. They almost always go first. You see the edge connector on these motherboards burning up because someone keeps replacing the resistors, and nothing else......so, at some point, the edge connector starts to burn (after all, it is the actual problem). So, your preventative maintenance just disabled your "early warning sign".
If you're going to do the sense mod.......at a bare minimum, replace the grounds and 5VDC pins in the edge connector (or have fun with a cooked motherboard in the future).
Rant over! (now go fix your edge connectors)
Edward