AML GP60 mods & improvements


 There's a number of little things I have seen that can be addressed:

  • number board lighting bleeds into cab
  • blue-white leds all over
  • Cab light LED grossly visible from outside
  • Kadee coupler conversion
  • additional speaker in tank
  • wiring change to allow shell to separate
  • rewire track pickup wiring and addition of PolySwitch PTCs to protect from shorts

Wiring changes to allow shell to separate from chassis

All the wires between the shell and the chassis have a way to disconnect EXCEPT the wires from the ditch lights, which originate on the chassis, but then go into the shell/cab, and then the wires plus more wires go back to the chassis through a plug.

Below is the chassis side showing the wires from the ditch lights. You can see the 4 wires turned into 3 (combining of 2 blue LED common):

original ditch wiring


I added a 3 pin "micro fit" molex connector on the 3 wires between the chassis and the shell. Make sure you don't mix up the black wires, so your left and right designations in the socket are still correct.

new ditch plug

Wiring changes to add short circuit protection

From bitter experience, I decided to add PolySwitches (3 amp solid state circuit breakers) to each track pickup lead to protect the internal wiring and pickup wiring in case of a short. (derailments on a switch often can cause a short between trucks).

I also took the opportunity to use both motherboard connectors, the front and rear ones for the track pickup connections. (the front and rear wires for both trucks were bundled together and used only one of the 2 track pickup sockets on the mother board.

The polyswitches are small enough they can fit through the hole in the chassis, so an added benefit is to allow removal of the trucks without unsoldering or removing the weird gray wire nuts.

Here's the system re-wired to have the track pickups for the trucks separated, by disconnecting the original wiring, and adding 1 more 2 position micro-fit connector, and using X1 and X14 on the motherboard. (this is not soldered yet until I confirm polarity for DC and DCC. I will add polyswitches on all 4 connections you see.

rewire track pickups




polyswitch wrapped

Blue-white LEDs

WTF? Really? in 2024?? So I have not decided if I will replace the LEDs with warm white, or cover with Tamiya yellow. Unacceptable 10 years ago. Absolutely nuts.

Coated all LEDS with Tamiya Transparent Yellow X-24 and made a difference. I removed the headlight/cab/number board assembly, and the rear headlight assembly. One coat for each LED. I carefully painted the clear lenses on the ditch lights. Might replace with warm yellow at some point

Contain number board light "bleed", and cab light reposition

The cab light is just a T5 LED floating in space, and mine was clearly visible in the cab, would have hit the engineer in the head. Fortunately, you can bend it up to nestle in the cab roof recess.

The number board LEDs can also light up the cab, I might put in a shield, but after toning down with the Tamiya transparent yellow, perhaps it's not so bad. Will take a look in the dark.

Interestingly, Colin's cab had a flat ceiling:

Apparently a detail that went by the wayside in full production.

Additional speaker(s) in tank

Since I use decoders that have 2 speaker/amplifier outputs (and can route different sounds to different speakers) I will add another speaker in the fuel tank, since it is empty. If you have never heard a setup like this, you are missing out. I normally put the horn and bell on the top speakers, and bias most of the prime mover below with spitters.

Since the supplied speaker is a 4 ohm (a bad standard choice, some decoders cannot handle this, but the QSI is no problem) I will put 2 speakers as large as I can fit into the tank, using two 8 ohm units in parallel. This really gives some bass.

The tank is 66.1 mm wide, and 192 mm long and 46mm deep. The underside of the chassis is smooth except for 2 bolts that seem to hold an internal weight in place. They come up under the motherboard, in recesses in the raised center spine on the top.

I bought 2 Visaton FRS7S (the S has a waterproof cone) and they almost fit, and sanded maybe 1/2 mm off the width of the metal frame on two sides. (a few seconds on the belt sander on 2 sides).

While fitting the speaker, I noticed that the fuel tank is double walled, there is a "box" inset into the outer tank casting. Measuring it looks like the bottom is 2.5 mm thick overall.

Will report more after cutting the holes.

Rotary beacon light

A functioning beacon light may be in my future, the QSI that I use supports 4 LEDs with adjustments to change the "speed" of the rotary beacon, and ramp up and down times.

Colin made one and it looks great:

I need to reserve ports for the light.

Misc info:

Camarillo Pacific makes the Campac coupler box for Kadee mounting, and it adjusts to get a precise coupler height.

I purchased a kit, and will install

Weather Underground PWS KCACARLS78