DC to DCC motor issue

[Potrail2378]

Hi, I have a class 43 HST. I have converted it to DCC, but now the motor doesn't work. I have unsolder all the wires and put 12vDC across the brush arms. The motor works really well, but if I connect the decoder, there is nothing going to the motor. There is no plug/socket arrangement, just hard wired. Thanks. 

[St1ngr4y]

Could you provide more details of the conversion you have done, in particular which decoder wires you connected to what. Also, which DCC controller are you using and how you configured the address of the decoder.

 

Ray

[96RAF]

Also please post a picture of the motor as Ringfield motors need special consideration because often the left hand brush is connected to the wheels on one side via the metal motor housing. You must interrupt this current path between both motor brushes and their associated wheels, before connecting a decoder or you risk killing the decoder.

[ColinB]

I don't know if you have done this, but if you have then accept my apology. If you have a multimeter, put the the HST on the track and check if there is any continuity between the the motor brushes and the track, It should read open circuit. It is usually a good idea to use an 8 pin socket, it is much easier to fault find. Basically if you have an 8 pin socket, there should be high impedance between all pins except pins 1 and 5 which should read somewhere between 10 and 100 ohms. The other thing to be aware of, is the stall current of a ringfield motor is higher than what a Hornby standard decoder can supply.

[Potrail2378]

OK, I'm not sure how to post pictures to the group but I have wired the - 

Red - track. 

Black - track. 

Orange - motor. 

Gray - motor. 

Blue - front & rear lights, cab and guard lights. 

White - white lights - power car, red lights - dummy car. 

Yellow - red lights - power car, white lights - dummy car.

Green - cab light. 

Violet - guard light.

 

Am using a Hornby Select, simply put power car and dummy car onto the track and programmed them both to address number 43.

 

Is there a way to test the decoder to see if it has blown? 

Thanks. 

[Chrissaf]

Posting pictures ... read TIP 8

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

[96RAF]

Once again Is it a ringfield motor or a can motor.

Have you check for open circuit between wheels and motor brushes. 

 

Your connections logic is correct but of little use if one or other motor brush is still  in circuit with the wheels.

[ColinB]

I see you have wired the lights in, so you can tell if the decoder is working, if you can switch the lights on and off. Do they change when you reverse the direction.

[Potrail2378]

It's a Ringfield motor, and no, I haven't checked for continuity between the track and the motor. Will do that tomorrow after work. 

[Fishmanoz]

It's the LH brush holder that may be connected to chassis and then to the wheels via the screw holding it.  The clue is if there is no external wire connected here, the return path is via chassis.  For detail on this, google Brian Lambert and check out Ringfield conversions on his DCC pages.

 

If there is a connection to chassis, the decoder will now be blown and you'll need a new one to try again after fixing the connection with nylon screw etc.

[Potrail2378]

Right, I've now unsoldered all the wires and started again.

Under DC conditions, the Ringfield motor works OK.

I have fitted an 8 pin socket and a brand new decoder. The motor now only goes in one direction - reverse even without any power from the Hornby select. Any ideas would be appreciated, thanks. 

[Wobbley Junction]

I had a similar issue with a Honby class 24. On the left side of the motor there was a connector wire from the motor chassis to the left brush spring. Even though I'd cut the wire to connect the track wire on the decoder I got the 'runaway' like you have. After lots of head scratching and mutimeter testing, not to mention loads of hair on the floor, I discovered an extra ontact behind the tag on the brush spring. Once I bent the tag away and put some Kaptan tape around the tag it worked. Hope this helps.

[96RAF]

As stated you must find and isolate the power path between the LH brush and the wheels, which is either a screw linking the brush to the motor housing hence via the axles to the wheels on one side or the brush sprung contact bears upon a protruding lug on the motor housing, easily isolated by filing off or insulating with tape or plastic shim.

 

Only then can you consider connecting a decoder into circuit.