Short-Style flicker on Digitrax Zephyr - but only on one loco

[Anonymous]

I was running a train today, and when it was running, my Digitrax Zephyr's display would flicker just like it does when there's a momentary short circuit. The loco is running as if it is like that too, jerking in time to each flicker.

Only one locomotive does this, however. the only time I've touched it since I last ran it (without this flickering) was to clean it's wheels. I did notice while holding it on the rubbing-alcohol-soaked paper towel while it was running that it would occasionally flicker just like this, except less frequent. 

I know it's the loco (an Atlas SDP35 with DCC a factory-installed duel-mode decoder), and I'm thinking that maybe the rubbing alcohol is shorting it out (does alcohol even conduct electricity?) so in mind of that I wiped the undersides of the trucks dry with a paper towel.

Can anyone help? The layout is HO. I've tried restarting the Zephyr (unplug and plug back in) and nothing is helping. An answer would be nice by tomorrow morning when an operating session may be happening...

Thanks in advance,

[jeffrey-wimberly]

I suspect that it's possibly a pickup problem, or there could be an intermentant problem with the decoder.

[simon1966]

Resetting or unplugging the Zephyr is  not going to make any difference if the problem is in the locomotive, which it certainly appears to be from your description.  Perhaps you have a loose or frayed wire inside the shell that is touching something it should not?  I would get the loco apart and inspect it to see if there is anything obvious.

[selector]

I agree with Simon.  It is definitely associated with this one loco, and it must be a bared wire or loose metallic something-or-other that is intermittently making contact with something that completes the circuit back to the base station through the rails.  I suspect that a combination of track wobbling and the stuttering itself sets up this ephemeral short, a sort of reinforcing loop. I would agree, too, that it is sure to be revealed once the shell is lifted.  It is highly unlikely to be found in the wheels and pickups.  Oh, and it could actually be the decoder, but I have no idea how to determine if that is true.

[Anonymous]

I tried resetting the Zephyr before I realized it was just that loco.

I'm guessing it's a wiring problem too, I just can't figure out what caused it to start mis-behaving now after about 7 years of perfect running.

On second thought, I did notice some sort of smell coming from it when I was cleaning the track, the smell you get from running a really old locomotive (dust burning?), which may have been the culprit.

I'll open it up tomorrow and check it out. In the meantime, does anyone know what type of decoders those AtlasMaster locomotives from 2001-ish had? It might've been a cheap decoder that fried or something.

Thanks for all the help so far.

[simon1966]

I think they had the equivalent of a Lenz LE1000 decoder.  Not positive about that but they were of the generation when the Atlas Master DCC system (made by Lenz) was on the market.

[Anonymous]

That's what I was thinking. Do you suppose the decoder migh've started to fry? It's about 7 years old now.

[simon1966]

It could be.  I had a loco that started to short and all that had happened was that the motor magnet had sucked up a bit of metal left lying around.  Could be something as simple as that.

[Anonymous]

I think I'll open it up when I get a chance and see if that's it. I really hope it's something that simple. I'd do it now, but I've had a really rotten day and messing around with small parts and figuring out how to dissemble/reassemble a locomotive is the last thing I need.

[WSOR 3801]

Shouldn't be too bad.  Getting the body off is usually the hard part.  A couple of screws hold the weights on, then the plastic covers hold the wires on.  Replace with most any drop-in style.  I'm partial to TCS.

[Phoebe Vet]

Sometimes a wire lays across something that generates heat.  Over time, the insulation can melt allowing it to short out.  It only takes a pinhole.

So, when you have it apart, inspect ALL the wiring, not just the decoder.

[Anonymous]

Well, I went downstairs to take it apart and figure out what was wrong with it, and on a whim, test ran it. It worked fine, with no indication there had ever been a problem! One theory I have is that some rubbing alcohol got in the truck, bridging the gap and causing the short. I don't know if rubbing alcohol even conducts electricity though...

I don't really think it's that simple, but I'm not about to go messing around with the wiring. It's it's not broken, leave it alone!

Thanks for all your help, everyone! Now I know who to turn to when I have problems like these!

[60YOKID]

Tyler,

Alcohol is not a good conductor, so it wouldn't be that.  And it also wouldn't be likely to have a faulty decoder since they either work or they don't work.

Since it occurred after you cleaned the drivers, I suspect some metal of some kind found it's way into the pick up area, and is intermittently causing a short.  Or another idea is worn out motor brushes.

Just my thoughts and good luck.

[Anonymous]

Well, as I had expected, the shorting started again. I'm going to open it up as soon as I can find the diagram to see how the shell comes off... Doesn't seem to be in the fuel tank like my U23B, and I don't want to risk breaking details by trying to pull the shell apart like Athearns...

Anyone got one of those blowup diagrams they can scan in for me? I remember putting all my instructions in one place so I wouldn't have to look all over for them... But now I can't remember where I put them...

[retsignalmtr]

i have a couple of the atlas sd 35's that run well with the dual mode decoder that has the plug to convert it back to dc. digitrax lists their DH 163AO as a direct replacement for the factory decoder. run the loco on dc to see if the problem is in the motor. i had the shell off on one to fix a broken wire. the couplers have to come out first then pry up on the shell is all that i remember as it's been a while.

[Anonymous]

I've got it open a while back, discussing it on the General Discussion part of the forum. Tonight I test it as per instructions from a member there. I'll let you know what I find out.