The problem

The problem is that Pins 3 and 7 are connected together on the underside of the PC Board. Plugging in a decoder with a NMRA plug, that has a function wire connected to pin 3 and turning on this function will result in this decoder function seeing a direct short between the function output pin 3  and the decoder function common pin 7. This will usually result in this functions output to be blown and no longer usable. This is the same common problem with the Atlas first release of U33C's, the Bachmann Doodle Bug. And now appears to be with Life-Like P2K GP7's and GP30's. The Fix!

The best fix is to cut the trace as shown in the picture on the right. This will make sure that any decoder that is plugged in will have it's functions safe.
There is another fix. This will leave the shorted pins on the SOCKET, but will prevent any damage to your Decoder function output.  If there is a wire connect to pin 3 of the decoder PLUG, remove from the PLUG. If there is nothing connected to pin 3 of the decoder PLUG you will not have any danger to your decoders function output.
Not all decoder manufactures have a connection to pin 3 on their NMRA PLUGS. And those that do do not always use a green wire. No matter if you choose this fix, just make sure there is nothing connect to pin 3 of the PLUG.

NOTE: It is also possible that this same socket will be found on other current and future releases from Life-Like. Be sure to check the socket before installing a decoder with a NMRA plug. Life-Like has been notified of this problem and hopefully will have it corrected with future releases of their great locos.

Also to be sure of no additional confusion on this. Please make sure you understand and know the difference between the PLUG and SOCKET. The reason I ask this, it almost appears to be what happened with Atlas, Bachmann and Life-Like.

The Install

The models are LL HO GP7 P2K  C&O paint #'s 5817 and 5813.

After the findings on the socket. I decided to hardwire the decoders. Besides the socket is large, and care would be required to use it. If you do be sure there is no chance of any wires shorting on the frame.
This is real dream install this way anyway. First LL used the NMRA color code, so it is just matter of matching wire colors all the way. Even the front and rear lamps match the NMRA color code. With both the diode board and socket out of the way there is plenty of room to work with.

Life-Like recommends changing the bulbs to 14-16 volts lamps. Other wise without a current limiting resistor, the stock 3 volt lamps would burnout quickly. I decided, what is wrong with adding resistor for the stock 3 volt bulbs.
After a little checking, the stock bulbs are 3 volt 50 mA bulbs. And the motor ohm'ed out at 16.21 ohms.  Deciding I was going to use the stock bulbs, with my layout set to Nscale voltage, my function outputs are 10.36 volts.
So 10.36 - 3 volts = 7.36 volts / 0.050 = 147.2 ohms for resistance. Seeing as these bulbs are 50 mA., they would be nice and bright, are mounted on the metal chassis, so I went with 160 ohms 1/4 watt for the bulbs. With the motor at 16.21 ohms, this would equal 12 volts divided by 16.21 ohms = 0.740 amps [740 mA] for the locked rotor [stall] current.

I decided to go with the DH140 decoders, the DH121 would work just as well. If you decide to use the NMRA socket then either the DH140P or DH121P would work fine. But I wanted Rule17 lighting, and I had the DH140's laying around. The decoders were pre tested so I knew they were ok. I hope you test your decoders before installing them.

I just placed the decoder forward in the slot where the PCB was. Taped it down with a piece of tape. Cut the leads to approx. 3/4 inch. And the heat shrink at approx. 1/4 inch. I cut the leads on the resistors close to their body. I first soldered the resistors to the white and yellow leads, this let me lay them down flat against the frame. The as I matched colored wires, I just cut the existing wires to match at the proper length. This gives one of the cleanest installs I have done to date. The run from decoder wires to loco wires is as straight as a arrow and only about
1.2 inches. And the heat off the resistors is almost none existent, as the frame makes a great heat sink. I placed them one on each side of the pocket.  I also placed a piece of tape over the wires to hold everything in place.

NOTE: It is always smart to be safe then sorry. Always place a new install on a current limited track before placing on the main. Such as a service mode program track or offline programmer like the PR1. Incase there should be a problem, this just might give you a second chance to correct it.
Placed each loco one at a time on the program track of the Chief, with WinLoc read each one. Everything checked ok.  So put each on the layout, they ran fine with factory defaults. Put the shells on each. And back to the programming track. Programmed the address of each loco. Programmed rule17 lighting, CV49 = '68' and CV50 = '78'. Put them on the layout and they worked as planned, lights look good, rule17 works either directional or with F4.  But start was to high. Took about notch 5 to get them to start rolling. After playing with programming the start voltage with OPS programming, setting CV2 ='10' [16 dec] worked about right. First notch will roll about 1
tie a minute.

Been running them since, they run great, typical P2K style, look excellent. After they get broke in, I may have to retire my Athearn GP9's.<g> Especially if they get some B&O GPs out. One thing I do notice, the GP7s are pretty smooth and quite right out of the box. More so then the SDs and GP18s.

I used the Proto couplers for now, but it looks like a KaDee #5 would be a drop in right into the GP7's plastic stock pockets with spring.

NOTE: If you run your layout on the HO scale voltage and want to use the stock 3 volt lamps, a resistor of 200 - 220 ohms would be in the ball park. On my system at HO track voltage the functions are output at 12.69 volts.  12.69 - 3 volts = 9.69 volts divided by 0.050 mA = 193 ohms so 220 would be a good choice. But the track voltage will very from system to system. So unless you know the exact voltage of your function outputs, these figures are just approx. and should make a good starting point.

Have Fun and Enjoy these great running and excellent looking Life-Like GP7s!
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