Hello--
Original poster here, and I'm just checking back here to say thanks for the tips that helped me fix my 6557 problem, which turned out to be swapping in a new 481-10 base plate. The plate finally arrived, and holding it in my hand, I could finally understand where the tabs are that need to be straightened in order to remove the old one.
It doesn't seem to be the best design, and though it took me a solid half-hour, I was finally able to get the four tabs up from the old one. The two tabs toward the center of the caboose were easier to access; the two at the end were impossible for me to get either a flathead or a small needle-nose onto. The two at the center took quite a bit of patience, as there was nothing to get leverage with and I had to be mindful of the fragile steps of the 6557.
After finally getting the center two tabs up, I had no luck in pushing the base off as I'd hoped. It's counterintuitive to ruin the old base even though I will be throwing it in the garbage anyway, but at last I mangled the base by pulling the whole metal section off the back of the axle with my needle nose.
I tinned the wire, pushed it into the hole of the new base, and soldered it in. The 6557 once again functions as well as it ever did, which is to say intermittent flickering of the bulb, and light wafts of smoke when parked in neutral.
Thanks again to everyone who chimed in.
