Melting DH126 - Digitrax Decoder

[elmertc19]

Good morning everyone,

I have a Kato DCC ready "Dash 9" locomotive that I use pretty reguarly.  I bought it new off E-bay a little more than a year ago and in that time, it has melted two decoders.  They've both been Digitrax.  I've tried searching for answers, but haven't really found too much.

Is there something I should check for or do to prevent this from happening again?  Attached are pictures of the decoder for that its worth.  You can some marks on one of the pins which I believe connects to the red wire on the harness.

 

Thanks in advance.

[gmpullman]

Hello, 

It sounds like what you are encountering is too high of a current draw than the decoder can handle.

Do you have a way to bypass the decoder (dummy plug) or temporarily remove the decoder and use an ammeter to measure just how much current the motor is drawing. You should also measure the stall current.

Some of the earlier decoders required more air space around them, too. If your engine is drawing close to 1 amp and the decoder is mounted close to the motor there may be too much residual heat that may not be able to dissipate.

Look for any binding in the drive train, be sure lubricants are not too gummy. Apply a tiny drop of fine oil to the motor bearings.

If none of this helps you might resort to looking for a decoder with a slightly higher current rating, but for a Kato loco the current draw should certainly be more in the 400-500 milliamp range, well below the max for a DH126.

Lastly, it may be possible the motor is simply worn out, or at least the brushes are.

Good Luck, Ed

[wrench567]

  Are they 8 pin plugs? I have seen some 8 pin plugs that actually went through the female plug and contacted the metal frame below it.

  Is it pulling heavy loads constantly? Any derailments?

  Service and lube the locomotive before installing another decoder.

  To tell you the truth, I have not had good experiences with Digitrax decoders. I had one smoke on a program track once.

    Pete.

[gregc]

have you measured the max current drawn by the motor?   (block the loco from moving allowing the wheels to spin)

is the decoder rated for at least that much current?

[gmpullman]

gregc

(block the loco from moving allowing the wheels to spin)

Stall current is measured by blocking the locomotive and not allowing the wheels to spin.

https://www.youtube.com/watch?v=7KbEVKZ2JhA

 

 

Good Luck, Ed

 

[rrebell]

Sounds like someone did not do a proper conversion to DCC. I bought a Kato NW2 off e-bay with DCC and even though I have not had a proublem yet, if they did not do the conversion properly and it derails it will need a new dercoder.

[snjroy]

I agree about the amps, that's what I would check first. There is no mention of short circuits, so it's unlikely to be the problem. I have installed dozens of Digitrax decoders, and only one has failed, by my own fault.

What I find intriguing is the fact that the loco is described as "DCC ready".  Installation should be straigthforward and pretty much any decoder should meet the amp draw. What type of Digitrax decoder did you use? Was the engine operating normally in DC mode? 

Simon

[NVSRR]

Well do remember the factory install dcc of Kato's sd80 Mac.  That little tab that fired and shorted many decoders.    Could this be a similar issue.  A small factory created short somewhere?   Ab bad factory wiring isn't out of the question
shane

[gregc]

gmpullman

gregc

(block the loco from moving allowing the wheels to spin)

Stall current is measured by blocking the locomotive and not allowing the wheels to spin.

 

sure

[Lakeshore Sub]

Elmerc19,

We can't see your embedded pictures so we don't know which version of the DH-126 you are using and what the decoder looked like after it melted.   I would think that is a 8 pin install since the that is what is specified in the Digitrax decoder selection tool.

Before each decoder melted, did you get a chance to check if the decoder became hot on a regular basis after use?   If it gets hot after each use, then the suggestions about motor amperage are most like the main issue.  If it does not get hot after each use, then I would suspect some type of short.

Scott Sonntag

[jjdamnit]

Hello All,

elmertc19

I have a Kato DCC ready...

The term "DCC ready" presumes that there is an NMRA 8-pin plug on the DC OEM PCB with a dummy plug and the motor is electrically isolated.

In theory...

To convert to DCC, the dummy plug is removed and the 8-pin to 9-pin DigiTrax wiring harness is installed.

Then the 9-pin decoder is plugged into the wiring harness.

In theory...

"I don't mean to be facetious or didactic, but..." Woody Allen; Broadway Danny Rose, 1984.

How do you know the decoders are fried?

elmertc19

...that I use pretty reguarly (sic).

How often do you run this unit?

Does it fry the decoder immediately upon power being applied- -booster turned on or commands sent?

Are you able to run this unit- -and for how long- -before it fries the decoder?

Is there physical damage to the decoder(s) that leads you to believe failure?

Thank you in advance for keeping us informed.

Hope this helps.

[rrebell]

Says he runs them all the time and that they melted. Also says nothing about factory installed DCC ready or what that even means as many manufactures have in the past said that only to find  it not to be true.

[SeeYou190]

I have one Kato locomotive that is "DCC ready". It is absolutely not a "Dash-9" anything.

It does not have an NMRA 8 pin plug. I think the Kato term "DCC ready" (in this instance) just meant the motor was isolated from the frame and there was a slot machined into the frame halves for space to mount a decoder.

Kato DC locomotives were a challange to convert to DCC because the motor was sandwiched in between two frame halves. These frame halves were both part of the electrical circuit to the motor. Isolating motors from these frames was very difficult.

Since this is just one locomotive, I have no way of knowing of this is typical of the majority of Kato models or not.

-Kevin

[gmpullman]

gregc

sure

       —enough

Regards, Ed

[mbinsewi]

I have a couple Kato dash 9's and I use the DH165IP.  I have no problems, not that this answers the OP's question, just saying.

The OP's pictures don't work for me, but I agree with others, there's a installation problem, maybe a direct short, and checking the stall current.

I wonder if this loco was really "new" ?

Mike.

[gmpullman]

Lastspikemike

Isn't maximum current draw just as the drive wheels lose grip?

Stall current is measured at operating voltage with the armature locked:

https://dccwiki.com/Stall_Current#:~:text=The%20stall%20current%20should%20be,the%20decoder%20that%20is%20fitted.

I had a few early Life-Like PAs that had motors that would normally run close to 1 amp but when stalled the current would jump to 3 to 4.5 amps. Life-Like chose motors with the wrong specs.

Cheers, Ed

[MisterBeasley]

How things change.  I remember reading on these pages years ago, probably in this very forum, that there was no consensus about exactly what was meant by "DCC Ready.".  Most of the engines I've purchased with that label had no plug for a decoder, and required a hard-wired job.  At first, I bought non-sound decoders with just wires, no plugs, and just wired them in.

I bought one of these DCC Ready locomotives from my LHS.  The owner took the engine apart for me and showed me what I had to do before installing a decoder.  I think it was something with insulating the headlight bracket.  I did that and never had a problem.

As I recall, it would only be a problem if a particular derailment caused an inappropriate current to flow through the locomotive.

DCC Ready may mean nothing.

 

 

 

[gmpullman]

Dear Alyth,

Lastspikemike

Sure, but when is that ever going to happen?

Traction tires, added weight, low torque motor, binding running gear.

Lastspikemike

They mean what I said, not what you say they meant.

Sounds like a word salad to me. You have life-long training in this department.

Are you saying "stall" current is measured without the motor being stalled? I'll quote our late forum friend, Randy Rinker in regards to this.

rrinker

 Step 1 - go to Harbor Freight and get the $5 or less multimeter. Last flyer they had a coupon for a free one, but I forgot to go get another.  

Step 2 - grab your old DC power pack, and a spare section of track. Plug the multimeter leads in for the 10 amp range. Connect one rail to the variable DC of the power pack. Connect the other rail to one multimeter lead (clip leads work great for this). Connect the other multimeter lead to the other variabel DC power pack terminal.

Step 3 - remove shell of loco and set on the rails

Step 4 - don;t forget to turn on the multimeter

Step 5 - hold the loco so it just spinds, crank up the DC power pack to full throttle. Note the approximate reading of the meter (it will be varying a lot I'm sure).

Step 6 - the hard part - while looking at the multimeter, grab one of the flywheels to stall the motor and note the reading. Do not hold it long, just to see the number.

Step 7 - shut off the power pack. If the meter reading in Step 6 was 1.0 or less, this is definitely not one of the problem motors and a normal HO decoder can be used just fine. Up to about 1.3 amps - check the decoder you plan to use for the actual steady and peak currents it can handle, but HO is 1-1.3 amps usually.  If you have one of the ones with the heavy current motor, it will be quite high 3-4 amps at least. Those will need new motors.

Randy

You can spell-check and analyze the grammar all you want, stall current is still STALL current.

 

Lastspikemike

The armature isn't ever going to lock.

Presuming the motor will never be locked (or stalled) is a gamble the owner will have to assume. I've had little pieces of ballast get picked up in the gearing. A new Broadway Limited SD9 loco I have had a small plastic chip in the worm gear housing, It would "lock" the motor, side rods bind.

Thanks for your valuable insight. I'll keep your advice in mind. In the meantime I will continue to measure stall current, especially with some of the open-frame motors I still have on brass engines, using the procedure Randy outlines above.

IMG_6621_fix (2016_08_17 08_08_12 UTC) by Edmund, on Flickr

There have been high-current motors installed in commercial locomotives, most recently in the Broadway Limited P5a and the Rapido RS-11s that have caused decoder failures. Some years ago there was a run of Life-Like PAs that all had high current motors.

Unless you test these to weed them out you WILL have burned or failed decoders. 

Lastspikemike

Nor do they mean the armature is prevented from spinning even though they say that they don't mean that.

 

THIS is from the manufacturer of the OP's decoder.

 

https://www.digitrax.com/tsd/KB466/what-is-stall-current/

To test N scale, use 10 volts.
To test HO scale, use 12 volts.
To test G scale, use 18 volts.
While holding the motor shaft or the locomotive so that the wheels don't turn, quickly turn the voltage up to the specified voltage and read the Amp meter.

^{(my underscore)}

Their grammar and spelling is superb. 

Better safe than sorry, Ed

 

[gregc]

The current that an electrical motor draws when its shaft if prevented from moving. This is typically the highest current a motor will draw. The stall current of a locomotive should be less than the peak current capacity of the decoder that is fitted.

Lastspikemike

I know what they mean and they do not mean the armature is locked. Nor do they mean the armature is prevented from spinning even though they say that they don't mean that. They mean when the armature isn't spinning at maximum applied voltage which is not what they wrote. 

the maximum current drawn by a motor is at max voltage with the armature not moving -- regardless of the wording

[richhotrain]

Lastspikemike

 

gmpullman 

Lastspikemike

Isn't maximum current draw just as the drive wheels lose grip? 

Stall current is measured at operating voltage with the armature locked:

https://dccwiki.com/Stall_Current#:~:text=The%20stall%20current%20should%20be,the%20decoder%20that%20is%20fitted.

I had a few early Life-Like PAs that had motors that would normally run close to 1 amp but when stalled the current would jump to 3 to 4.5 amps. Life-Like chose motors with the wrong specs.

Cheers, Ed 

Sure, but when is that ever going to happen? Actually, the link you posted is wrong grammatically. I know what they mean and they do not mean the armature is locked. Nor do they mean the armature is prevented from spinning even though they say that they don't mean that. They mean when the armature isn't spinning at maximum applied voltage which is not what they wrote. 

They mean what I said, not what you say they meant. This happens frequently on this board and in the hobby. Stuff is worded imprecisely and then misunderstood. 

Maximum current draw when the locomotive stalls by say hitting a track pin or other obstacle will be just before the wheels spin at whatever the applied voltage happens to be. The armature isn't ever going to lock. 

Geez, and all that Ed was trying to do was to answer a simple question. What a mess trying to sort through the above reply to Ed’s answer.

Lastspikemike

I know what they mean and they do not mean the armature is locked.

How do you know what they mean? Have you consulted with them?

Lastspikemike

Nor do they mean the armature is prevented from spinning even though they say that they don't mean that.

Assuming that what you say to be true is true, of course they would not mean that if they say that they don't mean that.

Lastspikemike

They mean when the armature isn't spinning at maximum applied voltage which is not what they wrote. They mean what I said, not what you say they meant.

lastspikemike vs. gmpullman. Reminds me of Ghostbusters. When you need an answer, who you gonna call? I’ll cast my lot with Ed any day.

Lastspikemike

This happens frequently on this board and in the hobby. Stuff is worded imprecisely and then misunderstood.

And yet this board and this hobby have survived quite well for all these years.

[gregc]

Lastspikemike

Exactly. But in our real model world only a few things can result in the armature not moving which is the effective maximum current the decoder needs to handle.

i hesitated to say stall current because it's hard for me to imagine how to prevent the wheels of diesel locomtive from spinning.   

but i can imagine the side rods of a steam locomotive getting caught on something and locking up the wheels

Lastspikemike

For a DCC locomotive the maximum current draw will be limited to the traction available from the drive wheels which may or may not coincide with maximum applied voltage

the maximum current is unrelated to traction (which is related to weight).

once again, maximum current occurs at max voltage with zero BEMF, in other words with the armature not moving.

Lastspikemike

I suspect the maximum amperage capacity of a decoder is designed with the normal maximum power capability of the locomotives it is intended for.

i doubt many decoders are designed for specific locomotives.    locomotive manuacturers select a decoder from decoder manufacturers that meets/exceeds their requirements.

modelers must select decoders that meet/exceed the stall current of the locomotives they are installing the decoder in, as pointed out repeatedly

Lastspikemike

Stall current will be the same whether you measure it just before the drive wheels begin to spin or after you briefly stop the wheels from spinning.

yes.   what is your point?

the decoder isn't damaged by the current momentarily exceeding it's rating.  it's damaged by the heat build up due to sustained excessive current.

it's conceivable that a decoder would be damaged at less than stall current over a long period of time with the armature not moving and not moving any air allowing cooling.

[SeeYou190]

richhotrain

Geez, and all that Ed was trying to do was to answer a simple question. What a mess trying to sort through the above reply to Ed’s answer.

After years on this forum I can cofirm that Ed's answers can always be "taken to the bank" with complete confidence. He is a deep fact driven source of accurate knowledge, experience, wisdom, and support.

The only times I know of where Mike is right is when he copies-and-pastes one of my answers as his own.

What a mess.

richhotrain

lastspikemike vs. gmpullman. Reminds me of Ghostbusters. When you need an answer, who you gonna call? I’ll cast my lot with Ed any day.

You know. LSM can attack me all he needs to. I openly admit I have very little idea of most of what you guys discuss. I am only good at three, maybe four, parts of model railroading. I have almost no knowledge of real trains at all.

I come to these threads to learn. LSM ruins a lot of this by "spiking" threads like he has done with this one. I find that very irritating.

His knowledge level is even lower than mine, but he tries to answer questions where he lacks any sort of the depth of information to be helpful.

LSM has run off some of the best providers of information we had in our ranks, and diminished the participation of others with his act.

Now, to attack the "Grand Poo-Bah" (I hope I got that right) of our group is completely unacceptable.

Where is the line drawn? 

You should jump right on that and make so much money that no one can ever doubt you again.

-Kevin

[maxman]

SeeYou190

You know. LSM can attack me all he needs to. I openly admit I have very little idea of most of what you guys discuss. I am only good at three, maybe four, parts of model railroading. I have almost no knowledge of real trains at all. I come to these threads to learn. LSM ruins a lot of this by "spiking" threads like he has done with this one. I find that very irritating.

I would urge you to have some wine, relax, and try not to let that individual bother you.

Lancaster County, Pa., is maybe 25 miles from here.  The Amish have a way of dealing with people who bother them.  It is called "shunning".  One definition is:

"persistently avoid, ignore, or reject (someone or something) through antipathy or caution."

[gregc]

Lastspikemike

It should be simple enough to build a decoder that won't accept more than x amps.

you say it's simple.   what do you think it would take?   

[Water Level Route]

Wow.  And to think I saw all the replies to this thread after not having read it for several days, I assumed progress had been made on helping the OP.  What a mess.

And yes, I'm saying what I'm saying and also what I'm meaning.  Not what you say i said but didn't mean even if I said it the way I said it, but meant what you meant but didn't say, even though you say you said it.  Oh brother. 

The DCC Wiki post is perfectly clear.

[gmpullman]

Water Level Route

And yes, I'm saying what I'm saying and also what I'm meaning.  Not what you say i said but didn't mean even if I said it the way I said it, but meant what you meant but didn't say, even though you say you said it.  Oh brother.

This is LSAT 101.

 

If you can't dazzle 'em with brilliance —

 

Will we ever hear from the OP again?

 

Cheers, Ed

[wrench567]

 I believe the OP has left the building.

 One other thing no one has considered is the fact we don't know what is burnt on said decoder. It could very well be the lighting circuit. I believe the spec calls for UP TO 100 milliamps. I had some 14 volt bulbs that drew more than that. 

  I hope this is clear.

   Pete.

 

[gmpullman]

I've had a few of the old DH-121, 123 and one or two of the later DH-126 decoders "melt". You can see the hot-spot where it burns right through the blue shrink wrap. I may have tossed a few in my decoder bin. I'll have to look later but I think I finally got rid of them.

Usually, for me anyway, when I blow a lighting output you don't see any physical damage to the decoder but the function is open on the minus side. I've had some Soundtraxx decoders that when a function output "shorts" it is always closed so the light remains on no matter what command is given.

On some where the blue wire 12V gets shorted it will simply go dead but the motor control will still work (OK for a B unit).

Good Luck, Ed

[gmpullman]

Lastspikemike

I'd buy and install an ESU decoder.

I had a run of Loksound Selects and Select Micros that were dead on arrival. ESU replaced two of them, the other three were over the one year warranty period and Matt Herman would not honor the warranty.

I've since installed over a dozen Loksound V5s that seem to be OK... so far.

Hint: Test your decoders as soon as you buy them!

Regards, Ed

 

[gregc]

Lastspikemike

I'd buy and install an ESU decoder.

https://www.esu.eu/en/news/read-news-entry/article/lokprogrammer-5012-verfuegbar/3/

LokProgrammer is not a decoder

Lastspikemike

My only point about stall current load is that it occurs when motor torque equals load.

again, max current occurs at max voltage with the armature not moving.   this is when there is no BEMF and the current is limited by the wire resistance in the armature, Ohm's law.   it's that simple