I am trying to put a Digitrax DH163D decoder in a brass 2-8-0 engine from Samhongsa Co. Ltd. Korea from Van Hobbies in Vancouver, BC. The engine is not new. I did the same thing with a 4-6-2 Pacific and it runs beautifully. I have a MRC Command 2000 DCC.
I had the 2-8-0 running good on straight DC. Then I only connected the motor. I took out the mounting screw and put double faced tape in place and made sure the motor was insulated from the frame. When I tried it on the track it ran quite rough, but it did run. I tried to make sure I was alligning the motor properly but it shorts out now as soon as I put it on the track. If I unplug the decoder it does not short out. There does not appear to be any short circuits in the engine. I wrote Digitrax and asked if I had ruined the decoder. The decoder is rated for 1.5 amps/ 2 amps peak.
Digitrax says I have a short in the decoder and that older brass engines are tricky and it is critical that the motor be electrically isolated and there be no way the outputs to the motor can touch any part of the brass on the loco or the motor will burn out and short. Open frame motors are particularily suseptible to shorting and can motors are recommended as they are almost always electrically isolated.
It looks like I have ruined 2 decoders and at $40 plus dollars Canadian I don't want to ruin any more.Should I try a different type of decoder? I buy whatever type the hobby shop has and choices are limited. Can I get a can motor? Where? How much? are they hard to put in?
I would REALLY like to get this engine running. Thanks for any help. You have helped me before.
Barry
Hi Barry
I've installed decoders in a few brass engines and as you discovered, they can be a pain. You need to get an ohm meter or at least a continuity tester and with the decoder unplugged put the engine on a short piece of isolated track. Many brass engines pick up one rail through the tender and the other through the engine and use the drawbar to get current from the tender. Are the insulating bushings OK on the drawbar pin? Even if you use tape did you put metal screws back in the motor? You might need to find nylon screws. There is a strong insulating tape "kapon" or such, it's yellow. That may help.Is current transmitting to the motor through the drive shaft? Even with rubber sleeves the tips of the shafts may touch.
With your ohmmeter check for continuity from either rail to either motor wire, there should be none. You even have to watch the cab roof overhang, it may touch the tender and short there!
If you don't have a vom you could use a battery and a bulb to check continuity.
ED
I've converted more than a few brass steamers to DCC, some with open frame motors. The important thing to remember is that the brushes have to be isolated from the frame, not necessarily the motor. To date, I've never had to actually isolate the motor from the frame. Are you sure you needed to isolate the motor in the first place?
If you want to test the decoder, put it in an engine you know that works. If the loco runs, then the decoder survived.
If you want to test the loco, put in a dummy plug and run it on DC. This way you can hunt down your short without the possibility of smoking a decoder.
It may be that the brush contacts are grounding on the shell (but highlly unlikely, IMHO), or some kind of frayed wire is grounding.
As for a new motor, try NWSL. They also sell gear boxes and many other brass drive parts.
Paul A. Cutler III*******************Weather Or No Go New Haven*******************
Check the motor brush connections. To same time and effort they often soldered one brush directly to the motor frame. The circuit was completed by the machine screw that fastens the motor to the frame.