Last week I had the opportunity to pick up one of the locomotives I've been eyeing for years: the MTH Premier P5A Modified (20-5590-1), the little brother of the GG1.
The locomotive had a good zinc-pest-free casting and the more desirable 3V Protosounds 2.0 command system, but wasn't in running order and was sold as a "repairman's special". The description of the failure-- "starts up normally but won't leave neutral"-- is one I have seen before in several other PS2 locomotives and is almost always related to the battery. When the P5A arrived I set it in my engine cradle and carefully opened it up. Disassembly is relatively easy-- there are four body screws on the very ends of the locomotive and two additional screws between the second and third driver axles in the middle.
When I opened the P5A I only had to unplug one connector to separate the frame from the body. I was very surprised and excited to see that this locomotive has command operable pantographs! I've never owned a locomotive with this feature before and didn't know that MTH had it available in the late 2000s.
Looking around at the P5A's innards, nothing looked out of place to suggest a more serious electrical failure. The locomotive includes the typical PS2 boards crammed in wherever they fit, crew figures, quite a bit of interior lighting and even a smoke unit to represent the operation of the steam generator.
And of course, there was the factory stock, 15-year-old 3V battery. These have a habit of puking battery acid when they go bad and making a mess of the inside of the locomotive (which is cleanable with a little vinegar but damages the battery harness), although this particular one seemed to have died peacefully. I replaced it with a 3V BCR which fit easily into the battery clip.
Here is the P5A back on the track with the BCR freshly installed. Check out those operating pantographs and the multi-color marker lights! Here's a tip on the pantographs-- you have to engage the switch underneath the locomotive AND pop the pantographs off the little balljoints on the roof to get them working. You can control the pantographs manually or set them to go up and down every time you change direction. The drive mechanism is set up in a clever way so that the pantographs will not be damaged if you forget to pop them off the travel locks.
Although the P5A was running again, its performance left something to be desired. The locomotive would stall or hang up on just about any track grade or unevenness in the track, to the point where it could barely run a complete lap of my layout at any speed. On close inspection I noticed that the locomotive seemed to be lifting one set of drivers off the track and spinning out. I found that the control switch for the automatic pantographs was sticking up enough to limit the movement of one of the trucks. I very carefully shortened the switch with my razor saw. The switch is still easily accessible with a screwdriver but doesn't touch the truck anymore.
I also removed the springs from the trucks to help keep more of the locomotive's weight on its powered drivers.
When researching known issues with the P5A on this Forum, I read that MTH put the the PS2 tachometer onto the motor that only drives 1 of the 3 powered axles and that moving the tach to the motor driving 2 axles would provide a performance improvement. Looking inside the P5A again, I realized that the wheels that "spun out" were the ones on the tach motor. I couldn't figure out how to remove the tach sensor, but I noticed that the motors and their brackets are identical. I ended up swapping the two motors inside the locomotive, which required pulling a bit of slack out of the harnesses and then desoldering and reversing the yellow/white motor leads to correct the locomotive's direction.
After reassembling for the final time, I ran the locomotive around my entire layout at 10SMPH to test for stalling. The results were very satisfactory. The following video shows the P5A pulling my Pennsy Fleet of Modernism coaches over one of the lumpiest track sections on the layout at 10SMPH. The locomotive does not stall on any of my bridges and the remaining issues I saw (you'll notice the train shiver a little at the end of this clip) were resolved by cleaning some grimy spots on my track.
Hope you all learned something from this! I'm going back to amusing myself by making the P5A's pantographs go up and down (like picking up bottle caps with a magnetic gantry crane, it never gets old!).