Is this a split frame type? Do you want DCC only or sound?  Joe

 If it's a DC engine,probably 12Volts.  Joe

Does the loco slow down only when the bell is rung or the horn blown? If so it's the decoder. This is a problem with Digitrax sound decoders. If that's the case, join the Digitrax yahoo sound group. The fixes should be found there.  Joe

I have a GP30 that is DCC on board. I'm planning on installing sound in mine as well. Here's what I found out: my unit is the split frame type, the motor is held in place by the frame. i believe the sound is from the motor vibration being transfered to the frame. On mine, I tok the frame apart ond ground down the frame where it holds the bottom of the motor. I took some caulking and put some on the frame. I put the motor back in the frame and made sure it was straight. I then put a bead of caulk on the other frame half and put the frame together making sure the motor was straight. I put the screws back in the frame . I took apatr the trucks, cleaned up the grease in them and lubricated them with oil. Reassembled the loco and ran it. It's still a little noisey but this made a big improvement in the growling noise. I noticed the motor still touches the frame on the ends. This is whrer the remaining vibration is coming from.  Joe

When you do get the PR3, look for a power supply of around 18v DC. The 14V power supply Digitrax sell for the PR3 is not powerfull enough. Just make sure the plug on the power supply is the right size and  polarity configuration. You'll need a computer to hook up the PR3 too. You might want to get Decoder Pro which is free. This along with the PR3 can programm decoders. It makes programm sound decoder easy.  Joe

Do you have another throttle hooked up to the Digitrax?E a UT4x or DT40xx? If yes,  you may have this loco on 2 throttles. You have to make sure it is dispatched from the throttle. If no ttry it on DC. could be a bind in the mechanism or bad decoder.  Joe

Sound like the motor got fried or the decoder. Look for discoloration on the decoder.  Joe

Since this is 1st gen. diesel, I use decoder # 828020. This is for a Bowser F unit, but has the keep alive caps built into the board. After I removed the PC board and LED holders, I looked at the top of the frame and decided where to mount the decoder. I had to grind off one of the mounting tabs for the old decoder. I then placed the new decoder upside down on the frame. I drew a line on the side of the frame where the front and back side of the caps where. I then drew a line on top of the frams connecting the side marks. This is the area I needed to remove. I filled in the area with a black marker. I then put the frame in a vice. To mill out the area, I scraoed a line down the center of the frame where the black mark was. I drilled a hole in the center of each side of the frame. I started with a medium small drill bit. Once the hole was drilled, I user a larger bit to open it up, then a bit that was slightly smaller than the diameter of the cap. This way you won't ruin the frame. When the holes drilled, I took my motor tool with a  reinforced cut off disc and made the holes into the slot pictured. I test fitted the decoder  to make sure it fit. I cleaned up the frame on the sides and top with a file. Remember to ware a mask and eye protection as there's a lot of metal particles coming off the frame.   Joe   

I put a piece of plastic under the deoder to prevent a short. Decoder Soundtraxx # 828020 speaker # 810054:1" diameter.  Joe

I have photo bucket but can't get it to work here. Any help you can give would be great. Joe

I have photo's of my sound install in a Bachmann GP7 but can't get them to post here. I did get them posted on the Model Railroad Hobbyist Magazine site(mrhmag.com). They are in their posts index section. Joe

I try and get some asap.  Joe

I got one of the new GP7's from my LHS last week and put in a Soundtraxx sound decoder in it( part # 828020). This is the board style with built in keep a live caps. I took off the top part of the frame and milled out a slot for the caps to fit into since the board had to be mounted upside down. I replaced the LED's with golden white ones since the ones that came with the engine were orange. I put a 1" speaker in the fuel tank opening(thanks Bachmann for this feature). The engine runs and sounds great.  Joe   

I had one of these that would work one way but not the other. Went to Digitrax web site and down loaded the instructions for theit AR1. The wiring diagram I got with the MRC unit was wrong. Wired it up according to Digitrax diagram and it worked. Try this first. How long have you been using the MRC unit? It could have gone bad. The one I had did.I replaced it with one from Digitrax as their's is adjutable on the AMP setting.   Joe

I have a PR3 and JMRI.  The problem some people have with the PR3 is the power supply. The PS14 from Digitrax is not powerful enough. I use an 18Volt power supply and have no trouble programming Soundtraxx, QSI, MRC, and Digitrax decoders.   Joe