Overheathing decoder - when reversing direction

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Overheathing decoder - when reversing direction

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Bernd		#1 Posted : 11 November 2007 19:16:53(UTC) Retweet
Joined: 09/05/2006(UTC) Posts: 25 Location: , Colorado		Hello All, Problem: Decoder overhests when trying to revers direction. I have 2ea 3021 loks that I am trying to convert. Both have been upgraded to the 5 star propulsion motor. First I used the decoder from Marklin kit 60921 - after a short run time it would not reverse anymore - upon closer inspection the decoder actually had a hole in the shielding (as in melted) - it still works in one direction only. I then replaced the decoder with the ESU LokPiolot 2 and the lok runs ok (not great but reverses like it should) But I really wnated sound so I installed the ESU LokSound MFX and again after a short run time, the lok would not revers anymore and the decoder gets very hot when I do try to revers (decoder stays cool when running in the other direction) - Using the same decoders on the other 3021 I have the exact problems. Both motors are brand new/clean. What am I missing? It seems to me that the decodeer is drawing to much current and/or has too much resistance when trying to revers and therefoe over heats. Did I burn out the decoder? Any advice/help would be appriciated!


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rschaffr		#2 Posted : 11 November 2007 19:33:34(UTC) Retweet
Joined: 03/01/2003(UTC) Posts: 5,180 Location: Southern New Jersey, USA		Check for a short circuit on the wire going to the rear light. Also verify that the wires going to the motor aren't shorted in some way. On thing you might do is remove the light wires altogether and see if the problem persists. Clearly the problem is in the lok, since it has appeared on a number of other decoders. Another thought..try to turn the drive wheels in both directions. If there is smooth motion in one direction and it is hard in the other, perhaps the gear train is jamming. Also try this without the brushes...if they are not worn evenly, it is possible (though unlikely)that they are creating some resistance to motion in one direction.
		-Ron Digital, Epoch IV-V(K-track/CS3/6021Connect/60216051), Epoch III(C-track/6021/6036/6051) http://www.sem-co.com/~rschaffr/trains/trains.html
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Webmaster		#3 Posted : 11 November 2007 21:31:36(UTC) Retweet
Joined: 25/07/2001(UTC) Posts: 11,162		One way to see if a power output transistor is "blown" is to inspect it visually and see if there is a little "bubble" or "brownish" dot on the housing... From your description, it sounds like something is wrong either mechanically or electrically in one direction and Ron's advice is the right things to check... Unfortunately, I think you have blown the output stage transistor for one direction in the decoders that do not work properly. Have you used the proper wiring method, and not accidentally connected "orange" (decoder output ground) to "brown" (chassis ground) for the lights in reverse direction? Orange and brown are both mentioned as "ground" for functions, but they don't mix, they are separate entities and should not be shorted at all.
		Juhan - "Webmaster", at your service... He who asks a question is a fool for five minutes. He who does not ask a question remains a fool forever. [Old Chinese Proverb]
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Lars Westerlind		#4 Posted : 11 November 2007 21:54:55(UTC) Retweet
Joined: 19/10/2001(UTC) Posts: 2,379 Location: Lindome, Sweden		I also agree. You say that it works in one direction only; with this (DC) motor is indicates that one of the output transistors habe been overheated. There is one (or two) of these for each direction. But what's the reason? I theory it shold not be becuase of heavy load, jamming, but you never know. Short circuit from blue or green, or motorshield connections to the chassis, is a rather reliable way to blow things. To much oil on commutator is another way, even though it should trigger the overload protection circuits before destroying. On the other hand, that it's in one direction you have problems, points to that there is something mechanical. I don't thik it has to with the lights; only blue and green cables should be regarded as it seems. /Lars
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Webmaster		#5 Posted : 11 November 2007 23:06:41(UTC) Retweet
Joined: 25/07/2001(UTC) Posts: 11,162		Lars, of course you are right but if orange is accidently connected to brown - it also affects the motor drive blue & green ground return on the board if motor power is applied and "backward" currents may blow components on the board when ground reference is wrong for the decoder outputs...
		Juhan - "Webmaster", at your service... He who asks a question is a fool for five minutes. He who does not ask a question remains a fool forever. [Old Chinese Proverb]
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Bernd		#6 Posted : 12 November 2007 01:42:28(UTC) Retweet
Joined: 09/05/2006(UTC) Posts: 25 Location: , Colorado		I disconnected all light conections - same. Don't know if this matters but the lok runs fine in anaolg mode and revereses easily. If the motor was jamming would that not display when trying to run the lok on analog? It runs even at very low speed and reverse and goes at very low speed the other direction. The wheels seem to move freely by hand even with brushes in place. The current wiring is (ESU Loksoundmfx): Red to pick up shoe, Black to solder plate under screw holding motor shield in place, orange to the right side of the motor and grey to the left side of the motor these are the olny connections other than the 2 brown wires which were already connected to the speaker. No pinched wires - did not even put the body back on after installing the decoder. Thanks again for you suggestions.


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Lars Westerlind		#7 Posted : 12 November 2007 09:22:21(UTC) Retweet
Joined: 19/10/2001(UTC) Posts: 2,379 Location: Lindome, Sweden		OK, I misunderstood. Your decoder does still work properly for a while, and also in analog? It's not severe burnt then. It's the reversing action in itself that doesn't work. In addition, rewersing works in analog but not in digital. It sounds weird in my ears. The only I can thing of is that it's a faulty decoder. /Lars
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