Can not read CV means that there is a problem with the decoder or locomotive. 14.8 volts AC on the track is good. Wheels and track need to be clean and dry, Decoder needs to be plugged in solidly. All the factory wires to the light board are good and solid. Did the loco work on DC before the decoder was installed? Check the wires to the motor. If there is no motor attached then you will also get the Can Not Read CV on the power cab. Try to remove the decoder and put the jumper plug back in and see if it runs on DC. Make sure the power cab is removed from the system before turning on the DC.
I think I may have found a problem. On the DH123P decoder I have the following soldered on the chip: white, yellow orange red, grey, blue. It appears that the black wire may have come off. There is a navy blue and green wire that look like function wires that are not connected and loose.
In any event does this chip (to someone who knows it) have 7 wires soldered in (which would include the black)? It seems that between the yellow and the suspected black wire is a blank. I’m assuming that the black wire is a truck wire…but wouldn’t one truck still work?..just want to make sure before I solder it on.
Just because the decoder appears to fit only one way does not necessarily mean that it is installed correctly. I have a couple Atlas engines where I have installed decoders and they require an extender to go between the decoder and the existing light board. An extender is basically a plug with 8 male pins on one side and 8 holes on the other side that accept the pins on the decoder.
The light board should have a little X mark or other identification that will tell you which is pin number one. The decoder should have some corresponding marking or identification that identifies pin one on the decoder.
I’m not saying that this is what is causing your problem, but I suggest that you go back and check just to make sure.
Position 3 next to the black wire is traditionally left empty, so that if you plug the 8 pin plug in backwards, nothing will get damaged - your loco will just run the wrong way - notice plugging it in backwards flips the motor leads as well as the track pickups. The track pickups have no effect on direction, however the motor wires being flipped will result in the loco moving backwards when the throttle says forwards.
The black wire is one entire side, not one truck, so no black = no power to the deocder = no movement, no lights, no programming, no nothing.
Well Pete it’s definitely been quite a day! I’m hoping that this knocks out the problem since I did still have no response with my other DH123AT chip for my bluebox Athearn. I’ll solder it in the morning and give it a go. Even if I have to come back I still feel that I’m pretty close to solving this either way. Many thanks to everyone for bearing with me through all this and the great suggestions and advice. The MR forums have always been a great source of knowledge and I’ve made some great friends here. Either way on what I find, I’ll send a post out on Tuesday with the results. Best Regards, Steve
Since you installed the decoder into an Athearn Bluebox locomotive, did you check to see that the trucks were isolated from the chassis before installing the decoder? If they aren’t, your decoder may have also gone poof!
Do you know anyone close to you who has a “knowable” working DCC-equipped locomotive that you can borrow? At least you’d then be able to confirm that your Power Cab is working properly.
Anything short of soldering the wires to the decoder can be problematic. Simply wrapping the bare wire around the decoder connector or using those little plastic tabs can result in loose connections and a “cannot read cv” message. Don’t ask me how I know.
Better yet, invest a few bucks in a decoder tester. NCE sells one for under $30. It works on all decoders, not just NCE.
Test the decoder before installation to make sure that it is good, and test it again if the installation fails to make sure that you didn’t burn it up.
Tom, you must not be familiar with Athearn Blue Box locos. On those locos, by default, the left-hand power pickup is routed from the truck to the frame.
That’s why insulating the lower brush clip is so important, and why the black wire in harness on the DH123AT the OP is using connects to the light bar that’s riveted to the frame, etc.
So no, if the frame is isolated from the left rail, and you haven’t modified the loco to make it so, then something’s wrong.
Well folks my Atlas Trainmaster is finally rolling [:D] though the front headlight isn’t (the rear light works). So I maybe have another loose wire to look at. I carefully soldered the black wire in with an 18W soldering tool, this is a royal pain!
Will now look into my Athearn bluebox GP-60, I did check and I made sure to isolate the frame from bottom clip w/ 3 strands of electrical tape. At least I know now that my system is working correctly! Will look into Rich’s idea of getting the decoder reader…great advice.
Of course I’ll be back if I can’t get the bluebox loco to work [:P] Thanks Again, Steve
I believe it will test both 8- and 9-pin decoders - no matter what brand it is. Here’s a helpful link for enhancing the NCE decoder tester from Tony’s Train Exchange web site.
Great, I’ll order one next week. I checked my decoder on wires white and blue for front headlight. Blue was obviously good since it’s the ground for both lights and rear light works. The white looks fine, checked the solder point all wires and decoder plug in…in fact I put the engine on a test track with straight DC and both headlights work, hate to be a bother any ideas? I’d hate to re-solder the point but I can do it if I need to, it looks good. Steve
Shazam I got the blue box working! It seems that with my Atlas and bluebox, part of the problem was that the decoder chip wasn’t in all the way, I guess I was being too careful, lol. Anyhow after pushing the decoder in and sanding down the frame and re-connected the black wire it worked fine.
Now I’m just trying to deal with my front light on my Atlas Trainmaster. [sigh] frustrating!
Reset the decoder. Through messing around perhaps you set the white wire to NOT be on when the loco is going forward. Since it’s a Digitrax decoder, program CV8=8 and then take it off the rails briefly. This will reset the address to 3, and set the white and yellow wires to be simple directional headlights that turn on and off with F0 (the headlight button).