Problem with DCC GP30

[ATSF_Ron]

One of the first locos I converted to DCC is my Atlas 90's era Kato GP30.  It's always been a great DC runner, and until a few days ago was also excellent on DCC.  I put in a TCS CN-GP decoder.  It ran fine from the git-go.  Yes, I was super careful wrapping the motor and contacts with Kapton tape and verifying it ran properly before putting things back together.  It also ran fine with the shell on for 5 or 6 operating sessions before having difficulty.  It just randomly slowed waaaay down to a crawl and wouldn't run any faster than a couple scale mph.  Lights work normally.  Took off the shell and it does the same thing.  Doesn't appear any wires are pinched.  I put a couple different DCC locos on the track and they ran fine, so there seem to be no apparent DCC system issues.  I plugged in a DC throttle and it ran normally.  Hmmm.  As you can see from the pics, the rear board soldering (2nd pic) looked suspect, so I redid those.  It's still not running, but lights come on as they did before.  I checked the board contacts to the frame and they are tight as a drum.

I'm not a great electrical gremlin problem solver.  Short of redoing the whole install, does anyone have a suggestion of where might be a place to start?  Thanks!

ATSF_Ron

[MK]

Did you try a decoder reset, CV8=8?  Your wiring looks fine.

[thomasjmdavis]

On my screen, looking at the middle picture, it looks like the orange wire may have a crack in the insulation where it goes through the hole in the weight.

Or, it could be my bifocals...

[ATSF_Ron]

@thomasjmdavis, I agree it's your bifocals, lol!  I think that spot you're looking at is the exact spot where the tape ends that's holding the wires. I double checked with optivisors and the wire looks good.

@MK, yes, I did a reset and it improved but is still not 100%.  The speed has gone back to normal, but it will randomly flicker the lights, stop, then immediately come back on.  As I've been looking back at my other TCS installs from earlier this year, I just recalled one of my GP30s (most likely this one) had a broken/cracked motor saddle.  I ordered a few extra from Atlas, and while I waited I went ahead and did this install.  Totally forgot about it until the order arrived from Atlas.  Then life got busy and I forgot again until just now.  I'll bet money that's the issue and it's causing an intermittent short to the frame. 

Thanks guys!  I have a bathroom tear out this week, so I'll put a post it note on the dang loco so I don't forget YET AGAIN!! 

ATSF_Ron

[ATSF_Ron]

Follow up...I tore everything down to the frame and motor cradle.  This is NOT the loco that had the broken motor cradle.  Apparently I need to take better notes when making these DCC conversions 

I needed to redo solder joints when I took it down to the frame, as the TCS decoder installs need "tight" wiring on the two piece decoders.  I inspected everything and all looked normal.  I put everything back together and all seems fine.  No idea what the issue was other than maybe a bad solder joint?  I did numerous switching runs through the turnouts and all appears normal.  Once again this loco is one of my best switchers and the very first airbrushed diesel I did back in the mid 90s.  Odd.  I could've sworn this one had the broken motor cradle.  Ah well, another mystery hopefully "solved," lol!



ATSF_Ron

[nickelplate759]

Just a thought - I have several of the TCS CN-GP (and CN) 2-piece decoders, and as you note they are very fussy about having tight connections to the chassis.   Would they be more reliable if one added jumpers from the front and back boards where they slot into the chassis?

[Lackawannae8]

I did notice you did not lightly build up any solder on the decoder to frame pad connection to give it some tooth to the chassis?

[ATSF_Ron]

@Lackawannae8 I did not.  The fit was tight as is.