Proto 2000 GP30 Drive Overhaul

In the spring of 2020 I purchased an undecorated Proto 2000 GP30 on eBay with the plan of eventually finishing it as TP&W #700. The seller's description noted that some paint had flaked off of the frame, which didn't seem like a big deal to me. I wasn't prepared for the mess that awaited me when I received the locomotive and took my first look inside the box. 

The paint was coming off of the frame in tiny flecks that coated the motor and drive train. It looked like someone had seasoned the mechanism with black pepper. I've never seen anything quite like this before and I don't know what would have caused it. It was a real mess, but I do enjoy cleaning and have been kind of looking forward to this project for a while because it will be very satisfying to get this unit cleaned up and operational. The tune-up turned into a rather involved project that took me several months to finally finish.

First, I completely disassembled the mechanism. A few more surprises awaited me.

There are four screws that attach the big weight to the frame. Two of them are at the ends and two of them are hidden by the fuel tank. I was not expecting the fuel tank to be attached with tape, and it was surprisingly difficult to remove.

I also wasn't expecting to find masking tape on the bottom of the motor. I guess this tape was intended to ensure that the bottom motor clip and/or orange wire wouldn't make contact with the frame.

I've read many horror stories of Proto 2000 truck gearboxes being filled with a grease that solidifies to a peanut butter-like consistency as it ages. I was pleasantly surprised to not find that stuff in my GP30.

It was altogether unsurprising to find that all 4 axle gears were split. This is perhaps the defining characteristic of Proto 2000 locomotives from the 1990s.

I discarded the axle gears and gave all of the remaining truck parts and universal couplings a bath in warm soapy water to wash off the oil and paint flakes. I gave the frame a bath of a different sort.

I soaked the frame in Super Clean degreaser for a couple of days to remove the rest of the flaking factory paint. A tennis ball can works great for this job. It has a tight-fitting lid, and it's almost the perfect size for 4-axle HO locomotives and 40-50' freight cars.

It would have been ironic if the Super Clean failed to remove the remaining paint from the frame, and indeed the frame didn't look much different after soaking for 24 hours. However, the surviving paint came right off with a little scrubbing with an old toothbrush under running water. I thoroughly rinsed the frame with water, let it air-dry, and repainted it with flat black spray paint from Ace Hardware.

I learned the hard way that it is essential to put insulating tape on the frame below the motor. I had completely reassembled the locomotive without this tape, and when I tested it on DCC it took off at a constant speed that I couldn't change with the throttle. Even though my ohmmeter showed no continuity between the bottom motor clip and the frame, adding polyimide tape between the motor and the frame solved the problem. Luckily the decoder was not damaged.

I opted to replace the Proto 2000 Blomberg sideframes with better-detailed Athearn parts. TP&W 700 rode on traded-in trucks from F3 #100. These trucks had a mixture of square and sloped bearing caps that differ from the roller bearings on the Athearn sideframes. The square and sloped bearings really stand out to me, especially because the trucks are painted silver, so I decided that it would be worth the effort to carve off the cast roller bearings and substitute aftermarket square and sloped bearing caps from Details West. 

I was hardly looking forward to carving off 8 cast-on roller bearings, but the job was less tedious that I expected. It wasn't practical to use a file to smooth the affected area, so I mostly scraped the area smooth with my knife.

After I finished carving off the cast bearings, I glued on the Details West parts with cyanoacrylate. Two of the prototype sideframes had 2 square bearings and the other 2 had 2 sloped bearings. The square bearings looked pretty good to me, but the sloped ones just didn't look right. The Details West parts seemed too bulky to me and not sloped enough, and they also have a bolted-on plate detail where the prototype is smooth. I looked into other options and found some Athearn Genesis parts. The photo above shows the Details West sloped bearing on the left and the Athearn sloped bearing on the right. The Athearn parts looked much better to me, so I carefully popped off the Details West parts with my knife, scraped off the dried glue, and glued on the Athearn parts.

When I went looking for alternatives to the Details West sloped bearing caps, I thought there was an Athearn option but I had trouble finding it. My searches for "Athearn sloped bearing" came up empty. Eventually I figured out why: "sloped" is misspelled as "slopped" on the package. Oops.

The locomotive made a squeaking noise when I test-ran it after installing the modified sideframes. The squeaking was caused by the wheels rubbing against the sideframes. I solved this problem by adding shims of 0.040" x 0.010" styrene to the backs of the sideframes.

I swapped out the 2,500 gallon fuel tank that came installed on the model with the 1,700 gallon tank from the parts bag. I didn't like the idea of securing the fuel tank with tape, so instead I used two 0-80 screws. It took me way too long to realize that the air reservoirs are supposed to snap over the sides of the frame. Until I figured that out, the fuel tank was a really loose fit.

The Proto 2000 GP30s came equipped with low-voltage headlight bulbs. I decided to replace these with white LEDs. I used NTE #30143 white LEDs that I bought at Micro Center. These LEDs come packaged with 220 ohm resistors, but these were too small for my application. The spec sheet for these LEDs list a forward voltage of 3.2 V and a maximum continuous forward current of 25 mA. On DCC, I measured a voltage of 13.6 V across the headlight pins. I calculated the minimum resistor needed using Ohm's Law as follows:

The closest available resistor at Micro Center was 470 ohms, and the next size up was 1,000 ohms. I bought and tested both. These LEDs are extremely bright and I didn't notice much difference in brightness when using the 470 ohm versus the 1000 ohm resistor. I ended up using the 1,000 ohm resistor to keep the current well below the LED maximum. 

The LEDs I used, and the assembly I made for the rear headlight. The resistor is on the cathode (negative lead, yellow wire) under the heat-shrink tubing. The resistor can go on either the anode or the cathode; most examples I found on the web show it on the cathode for some reason, so I did it that way too.

Converting this locomotive to DCC was a real headache, though I have to admit that I made it a lot more complicated than it really needed to be. TCS makes a decoder, the LL8, that is designed to be a drop-in replacement for the original circuit board in these locomotives. However, the LL8 is quite a bit more expensive than other TCS decoders that are more universal and have fewer functions. My cheap side won out and I opted to trade what I thought would be a little more work for a less expensive decoder.

The TCS website has a helpful library of decoder installations in a wide variety of locomotives. After looking at several different installations in similar Proto 2000 locomotives, I opted to try the DP2X. 

I reconnected the wires to the 8-pin socket so that it would face upward. I covered the frame below the plug with polyimide tape to prevent a short. I used one of the original circuit board mounting screws to hold the socket in place. 

The DP2X is a tiny circuit board that plugs right into the 8-pin socket.

Everything seemed good with the DP2X installation until I test-fit the body shell. The shell fit, but the DP2X was pressed up against it. When I test-ran the locomotive in this configuration, the shell did get warm from being in contact with the decoder. I doubt the decoder would have gotten hot enough to melt the plastic, but this still didn't seem like a good permanent setup. I installed the DP2X in my Atlas C424 (TP&W #801) instead and went back to the drawing board for the GP30. 

I ended up using a TCS T1 instead. I thought about hard-wiring the T1, but had I done so I wouldn't have been able to disassemble the locomotive again without unsoldering or cutting wires. I ended up keeping the Life-Like 8-pin socket and using a Digitrax short harness to connect the 9-pin plug on the T1 to the 8-pin socket.

Here's the locomotive along with the T1 decoder and the Digitrax harness. I had to rotate the 8-pin socket by 180 degrees from how I had it set up for the DP2X to get the pins in the correct orientation to use the harness.

Here's the final installation. The wires on the "short" harness were still a bit too long, so I had to gently put a Z-bend in them to get the decoder to sit where I wanted it. In this configuration the top of the 8-pin plug might touch the shell, but the decoder definitely won't.

The shell fit just fine on the reassembled drive with the T1 decoder. The truck sideframes look great, and I'm glad I took the time to modify the bearing caps.

And with that I finally have the GP30 drive ready to go. I'm going to take a break on this project for a while and paint the shell for TP&W 700 at a later date.