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I just installed a decoder in a brass sharknose and It has a short that occurs when the locomotive is placed in speed step 1 in either direction. It does not short until this is done. The light works and the headlight function works fine, but when speedstep is applied it shorts out and trips the circuit breaker to the track. I can't find any wiring problems but I am wondering if this is a problem with brass locomotives. I found a few shorts when I was checking the locomotive before I installed the decoder.  (this is install 65 or 66 so I am not new to this) 
Charlie
Charlie:

Is the motor fully insulated from the frame/pickups?

(I don't do DCC, partly because I have a lot of heritage locos where the frame forms the motor frame and one brush is powered by it.)
Yes, the motor is isolated in fact there are two of them and they are both isolated. I have put decoders in heritage Atlas, Athearn and Bachmann as well as many early Proto 1000 and 2000 engines. It isn't that hard to do, All that needs to be insulated are the motor brushes. I thank you for asking because it makes me rethink everything. I checked everything with an ohm meter and tested the unit with DC to see the current draw. The draw was 3/4 of an amp for both motors. I am now leaning toward a bad decoder. I will check that out this week. Thanks.
Charlie
If you're using a single decoder to run both motors, could the leads between the motors be reversed? (just a suggestion).

Dan
(07-11-2022, 09:16 AM)DanRaitz Wrote: [ -> ]If you're using a single decoder to run both motors, could the leads between the motors be reversed? (just a suggestion).

Dan

Good suggestion Dan. The motors are wired in parallel but they run in opposite directions, with a drive shaft between them. one motor goes to each truck. That worked on DC but might be a problem with DCC. Thjanks
Charlie
@ Charlie B

Which type of motor are in your sharknose?

[Image: dsc02513qru7z.jpg]
This one?
And two of them?
And you really want to toast your decoder Icon_question  Icon_e_wink

If this type is really mounted, then get rid of them. They are electric current guzzlers.





[Image: dsc02514icu9z.jpg]
And often one brush is not insulated. Meaningly both brush holders seems insulated, but often too the path for the electric current is hidden and not clearly visible.




[Image: dsc03166slsfk.jpg]
Here i have replaced this old motor with a Mashima 1833 can motor and the hardened rubber universals were replaced by A-line ones.




[Image: dsc03231svu1r.jpg]
And remember, with this brass Diesels one truck is insulated from the main frame and the other is conductive for electric current. Do not interchange the trucks.
And for DCC it will be much better to make additional wipers for a more reliable current pick up.



Lutz
Thanks for the reply. This unit was redone with 2 new can motors and was detailed nicely. It ran on DC with a current draw of less than 1 amp total draw at stall. I don't know the brand of motors as they don't have a visible mark but they are can motors. I must do some more research to see if I can find a name on them. I will attach a photo. If you see something please point it out. I am to the age where I spend hours hunting a tool that is in my hand  Icon_e_biggrin The one black wire would be white for the light but the installer already had an LED and resistor installed and it was neat so I just used his wire. The light works fine. I double checked and the brushes are insulated from the frame and so are both the front and rear trucks.[attachment=38838] I will add that the locomotive was sent out to be redone and the owner died while it was being done. The son that sold it was not into trains so it wasn't run. It did run nicely on dc but did have portions of the trucks that could hit the frame and short. Easy fix because it was a hidden part of the front frame. 
Charlie
Charlie,

these can motors seemed to me that they are of superior grade. But i recommend to remove this silcone hose between the motors. It makes no sense there.
Then try again. Do they run in the same direction?


Lutz

... sometimes desperately searching for my eyeglasses and at least finding them sitting on my nose ...
(07-12-2022, 06:01 AM)Schraddel Wrote: [ -> ]Charlie,

these can motors seemed to me that they are of superior grade. But i recommend to remove this silcone hose between the motors. It makes no sense there.
Then try again. Do they run in the same direction?


Lutz

... sometimes desperately searching for my eyeglasses and at least finding them sitting on my nose ...
Yes Lutz, they do run in the same direction.  I think the silicone connection is to help keep the motors in sync. Actually I don't see a reason for 2 motors and I may figure a way to eliminate one of them. 
Charlie
Charlie,

My guess is some sort of ground loop. Somehow your motor circuit is not isolated. I would probably start with insulating the DCC decoder and then check every wire connection (even the lights and accessory functions) for a stray strand that touches metal. Can be really frustrating with all of the metal in that model! Retrofitting can be really rewarding or very frustrating until it's rewarding. There's also the possibility that a short hit a component on the DCC chip and fried it open.
Charlie, if this was running on DC before the decoder was installed make sure your decoder is wired to each motor correctly. Has a matter of fact I would do just one motor, disconnect the other one from the drive train.
Get the one motor running then with the other motor still not hooked to the drive train. The put jumper wires from on motor to the other and check witch way the motors turn.
(08-19-2022, 07:07 PM)woodone Wrote: [ -> ]Charlie, if this was running on DC before the decoder was installed make sure your decoder is wired to each motor correctly. Has a matter of fact I would do just one motor, disconnect the other one from the drive train.
Get the one motor running then with the other motor still not hooked to the drive train. The put jumper wires from on motor to the other and check witch way the motors turn.

Thanks Jerry,  I did not run this on dc on the track, just used a couple wires to the wheels. I don't see any way it would have run on DC on the track. The trucks are full of shorts so I am changing them with a pair I have from a PA1. when I get back to the project.  I will write how I did it including photos. It looks like a fairly easy job.  The motors and the decoder check out fine. 
Charlie
Charlie,

these beasts have wheelset insulation only on one side. Meaning there is only 1 wheel of the wheelset insulated.

Are all insulated wheels on the same side Icon_question
To check that out remove the sideframes and put the loco onto a DC powered track.

And for other shorts; how much is the lateral play of the wheelsets in the trucks?
Is there any possibility, that an insulated wheel is able to touch any part of the sideframes or gearbox?


Lutz
(08-21-2022, 01:08 PM)Schraddel Wrote: [ -> ]Charlie,

these beasts have wheelset insulation only on one side. Meaning there is only 1 wheel of the wheelset insulated.

Are all insulated wheels on the same side Icon_question
To check that out remove the sideframes and put the loco onto a DC powered track.

And for other shorts; how much is the lateral play of the wheelsets in the trucks?
Is there any possibility, that an insulated wheel is able to touch any part of the sideframes or gearbox?


Lutz

Lutz all of the side play issues are present. The insulated wheels however were done right. That is why I think donor trucks will be the easy fix
Charlie
Well the BP20 is alive and well. I used a set of donor trucks from an Alco DL 109 along with the motor. I had to make a longer drive shaft for the rear truck. 
I installed 3 oz of weight and there was lots of room for the decoder. After the work to install the trucks and I used silicon to mount the motor, the decoder installation was a 10 minute job and everything works fine. A little tweaking of the cv's and I will move on to the next project. I am glad to get this one off the work bench. 
Sorry but I didn't take photos but it was pretty much up front once I went the complete change route.  Icon_e_biggrin
Charlie