Atlas HO GP38 dcc problems...

Model Railroader Electronics and DCC
1

I’ve got a recently-released Atlas GP38 that is giving me dcc problems.

I’ve read other threads (usually regarding Bachmann) about capacitors on the light board that interfere with proper dcc operation. I’m wondering if that’s the case here.

Some background: I received the loco about 10 days ago. This was the “DC, dcc ready” version and I had read that it came with an 8-pin connector. OK, I have a few spare 8-pin decoders (Digitrax, TCS).

It ran ok out-of-the-box on a short test track using DC.

I took the shell off, and found there was not only an 8 pin connector on the board, but a 21 pin as well, with what looked to be a “dummy plug” plugged into it.

I pulled off the 21 pin dummy connector, and tried a TCS 8 pin decoder. The engine ran and I should have left it that way, but the headlights were giving me problems. Time to try another decoder.

Swapped it out for a digitrax DH166 or 126. Now… doesn’t run.

I’m using a Roco z21 running on a Samsung tablet, so went to the programming pane and tried some basic commands. I was getting an error message to wit: “command could not be entered, decoder failed to respond”. I don’t recall ever seeing that error before (and I have at least 25 other locos).

Hmmmm… maybe the 21 pin dummy plug is supposed to remain in place? I put it back and… POOF! Smoke from the 8 pin decoder. Nope, that’s not it. [:O]

So I took off the 21 pin dummy again, and re-connected the TCS decoder – and now, it won’t work, either.

In fact, none of the other four 8-pin decoders I have would run the engine. The lights would activate, but the loco wouldn’t run.

So… I ordered an ESU LokPilot 5 21-pin decoder. I have older ESU decoders in three other locos and they work very well.

Put the LokPilot 5 on the 21-pin connector and the engine runs and lights work. BUT… it doesn&

2

OE,

Since you outfitted your GP38 with a LokPilot, try running the Auto-tune feature before snipping off any caps. To do this:

  1. Go into your DCC systems programming mode
  2. Set CV54 to “0”
  3. Exit programming mode
  4. Press F1 on your throttle

Either do this on a roller test stand or on a 6’ length of track because the locomotive will take off at full throttle for 2-3’ then suddenly stop. It might fix your issue…or it may not. It’s worth a try.

You could also try hardwiring the decoder rather than use the 8-pin socket. You’ll need to add resistors if your headlights are LEDs or 1.5V incandescents.

Tom

3

tstage:

I tried the “auto-tune” previously, didn’t fix the problems.

I’ve considered tearing out the existing wiring for a “new board”, but…

… that seems overkill for a new/recent engine.

I may try a different 21-pin decoder, perhaps a Soundtrax. I’ve used ST products and have been satisfied with their performance.

If a Soundtrax decoder behaves the same as the ESU, may have to tear out the factory wiring. But again, this shouldn’t be necessary on a new product.

I considered it could be “mechanically-based”, but the motor/drivetrain turns freely by hand, with no indications of binding, etc. …

4

OE,

I would think after the 3rd decoder attempt that the board is the issue and trying yet another decoder would be a waste of $$$.

I would try removing the current lightboard completely and “temporarily” hardwiring one of the decoders to the chassis wiring to see how it runs. If that fixes the issue then you can either 1) hardwire your decoder of choice permanently, or 2) use a Decorder Buddy board for making your connections. I’ve never tried the latter personally but users seem to be pretty happy with them.

You might also want to confirm with a multimeter that the motor brushes are isolated from the chassis. Some older locomotives are not isolated and this could be problematic should you inadvertently derail and the magic smoke is released from your decoder.

Tom

5

I think that you need to remove the 8 pin plug. Bet it has pins shorted so it would run on DC.

6

I know the capacitor issue came up with some early “DCC ready” Bachmann engines, I don’t know that it ever was a problem for other manufacturers.

I suspect the second decoder had a problem before being plugged in, could be the first one did too (or if it needed some adjustments re the lighting)? Also, I wonder if the ‘puff of smoke’ you saw that apparently fried the one 8-pin decoder didn’t also affect something in the greenboard and that is causing the trouble with getting an 8-pin to work.

If the engine is now working with the 21-pin decoder but just not running as smoothly as an Atlas engine should, you could (if you haven’t already) do a break-in run: 10 min. or so forward at about 3/4 full speed, then 10 min. in reverse. Then maybe lubricate the moving parts. That could be all it needs at this point.

7

“Recently released”? bought used or new old stock?

The Atlas site shows a sold out GP38 which utilizes an 8 pin decoder socket. No mention is made of the 21 pin version.

Is it possible someone had messed around with this locomotive before you got it?

If it’s really brand new why not make a warranty claim?

8

I miss read your post- I was thinking you were using the 21 pin connector to use a decoder- not sure why you destroyed a decoder using the 8 pin plug as long has the 21 pin jumper was removed.

better take a good look at the light board for a short some place.

9

The engine runs (movement, lights) with a 21-pin decoder (ESU LokPilot 5).

There is nothing in the 8-pin connector with the 21-pin decoder attached.

BUT… although it runs, it seems to run erratically. It will suddenly “jump up” in speed – as if I put on 15 more speed-steps (but nothing has changed). It seems more “electrically related” than “mechanically related” to me. As if the dcc board was reacting to inputs that I didn’t make.

And then… it will go back to running ok. As if a switch had been flipped on/off.

The drive train doesn’t seem to be binding up. Something else. I could be wrong.

This is a relatively new release – Atlas HO product archive shows these as having gone into production around 2018. Conrail #7880 with the “white stripe”.

Since I can’t get any 8-pin decoder to work, I’m going to try a second 21-pin decoder (which I don’t have yet), and see if the problems recur with that…

10

I still think you should try removing the lightboard before purchasing another decoder. Then you’ll know for sure whether the lightboard is the source of the issues or not. But that’s just me…

11

I sympathize with your problems. I’ve had one decoder fry on me in 16 upgrades.

I must have really old stock because I’ve not seen a 21 pin socket on a GP38 either. The 2 GP38’s I have are really old and had filament lights no less.

The GP38 is probably the easiest loco I have ever had to plug in a DCC board. Remove the dynamic brake cover on top and slide it in and shove the sugarcube speaker in there as well. Yeah, old stock release…
My GP38-2 had LEDs and was a 5 minute DCC upgrade with a Loksound v5 DCC (58820). I wish they were all as easy. (Looking at you Atlas Dash8…)

However, back to being relevant, with my GP38, what I did was get a Loksound 5 DCC Direct (58821) and simply replace the entire light board assembly and wire in some LEDs. Easy job and no Atlas electronics remain in there. A bit of soldering was all it needed.

Good luck sorting this out.
Like others have pointed out, I’d not be using that existing lightboard any more.

12

He put the 21 pin jumper plug back in (with the 8 pin decoder still plugged) in when he couldn’t get the 8 pin decoder to program.

Is it possible the loco is selected on more than one throttle? That’s exactly what it sounds like but I’m not familiar enough with Roco to know if it’s possible.

13

Maybe check that the decoder wasn’t at some point added to a consist? That can cause similar problems.

14

The OP stated he had purchased a LokPilot 5 decoder to try in the locomotive so that shouldn’t have been in any consist. The idea by Robert that the locomotive might be acquired by more than one throttle has some merit.

Tom

15

Oldngrey wrote: “However, back to being relevant, with my GP38, what I did was get a Loksound 5 DCC Direct (58821) and simply replace the entire light board assembly and wire in some LEDs. Easy job and no Atlas electronics remain in there. A bit of soldering was all it needed”

That one looks like it would drop right in, BUT, I don’t want sound. Just motor control. $90+ is a lot for a decoder that’s only going to be used for motor control…

To answer wjstix – I have no “consists”, the railroad and the way I run it is too small for that. Every engine I own runs “as a single unit”.

A gripe: I had good experiences with ESU decoders up until this one. I have three other ESU units, all three have the #53614 21-pin decoders, and all three run great.

But the 53614 has been superseded by the #59629, which is what is in the GP38. And, compared to the older decoder, this new one has “feature-itis”. A bit too complicated for my tastes, particularly the function table setup (as accessed using JMRI).

I’m thinking of trying a Soundtrax 852005 just to see if it improves things. I believe the ST is “more basic” and I’m really just interested “in the basics”, anyway.

16

ESU makes a motor only version they brand LokPilot 5 (59629). Much cheaper than Loksound and same connections and basic footprint. There’s a new one about to be released.

17

Not to hijack a thread but could you tell me what decoder you used with the sugar cube speaker and 8 pin plug.

I have the same Atlas Locomotive but with a notor only decoder.

18

No thoughts on whether or not it could be selected on more than one throttle?

19

Robert wrote: “No thoughts on whether or not it could be selected on more than one throttle?”

Sorry, this makes no sense to me.

I use a Roco z21 control box and for my control surface I use a Samsung 9" tablet. Every loco (about 27 or so now) is represented by its own screen, I use a horizontal orientation so I have 2 locos side-by-side at any time. When I select a loco, it’s number and pic is displayed, and no two engines have the same number.

GP38 7880 (the one that has the problem) can’t be controlled from any other loco’s screen. Whatever is affecting it is something “self-contained” to/in that unit.

Since my 8-pin decoders won’t work with it, I need to try another 21-pin decoder, but don’t currently have one at the moment. So this is on the back burner until I find another to try…

20

To check to see if the motherboard (light board) is still ok and not a possible cause put dummy plug back on and check it still runs ok in DC mode.

I infer the 21 pin mini board “plugs into” (wired in so as to in effect short the pins that a dummy plug would short but at corresponding pins at thec21 pin socket) the 8 pinsocket so, in effect, the 21 dummy plug bypasses the decoder at both the 8 pin and the 21 pin sockets. There would not also be an 8 pin dummy plug. But if there are two dummy plugs put them both back in and test for DC only operation.

The photo you show of a similar model does have a dummy plug in the 8 pin socket. Are you sure yours doesn’t also need one there when the decoder plugs into the 21 pin socket? You haven’t confirmed whether your locomotive is new from the manufacturer or retailer. Is it possible it was suppled to you with an 8 pin dummy plug missing?

As nobody has yet answered your question about capacitors for RIF the answer is yes, EU requires more robust RIF suppression than we do over here. The capacitors known to give running issues when left connected are in Bachmann light boards. Decoders now have their own RIF suppression so the lightboard capacitors can cause problems with the on board RIF components. The doubled up RIF doesn’t prevent the locomotive from running but they interfere with the decoder control of the motor.