Decoder Problem on Older Loco

[2027Joe]

Hi All

I am in the process of fitting decoders into some older locos.

The loco's in question, at the moment, are the Hornby R253 Dock Authority Shunter.

I have completely stripped and cleaned all parts as thoroughly as I can, fitted new brushes and removed all the bits not required for DCC operation.

I have fitted a Hornby decoder in another one, and all is well. I then did exactly the same on a second one and I run into the problem.

I am using the same Hornby decoder which fitted in fine. The problem now is when going forward the loco is great. However, when I put it into reverse it shorts out !!

I have checked all my connections and they appear to be ok, and exactly the same as the first loco, which is working properly.
There are no parts of the wiring harness or decoder touching anything and the wheels are correctly fitted back in the chassis.

What/where am I doing/going wrong? Any ideas please ?

Thanks in advance for any suggestions.

Joe

[Rog (RJ)]

The motor is possibly drawing too much current. Older locos tend to draw more power than newer models and you may be on the limit of what the decoder can supply. 500mA is the rated running current for the Hornby R8249 decoder.

You should really do a Stall Current test to see what current is being drawn by the locos before fitting a decoder.

You could try a Lenz Standard decoder or a basic Zen decoder which can handle the power demand better.

Edit. I meant Zimo, not Zen.

[2027Joe]

Rog

Thank you for that.

I hadn't actually done the stall test prior to fitting the decoders.

However perhaps I will do so nowafter I have undone the Hornby decoder.

Thank you for your advice.

Regards

Joe

[RAF96]

Which motor are we talking about, the old Triang type vertical motor bogie, ringfield or XO3/4 or a modern can.

If its one of the old motors and the current towards stall is worse in one direction than another then check to see if the commutator has been moved away from alignment with the armature poles. The effect of any offset is a bit like advance and retard timing on your old car, At dead stall the current should be the same in either direction as the motor is stationary at that point.

[2027Joe]

RAF 96

Thank you for that.

The loco's are the "Hornby Triang" models with the X03/4 motors.

When I do the stall test I will see what the readings are.

Thank again for the heads up.

Joe

[Brian]

RAF 96

Thank you for that.

The loco's are the "Hornby Triang" models with the X03/4 motors.

When I do the stall test I will see what the readings are.

Thank again for the heads up.

Joe

Hi
I assume this is the motor with the Vee spring along its top? If so BOTH arms of the Vee spring MUST BE ISOLATED where the springs arms touch the brush tops. If possible use a piece of the original insulation that was on one arm (cut it in half if its long enough) or use a short piece of PVC wires insulation of the smallest size possible that will slid onto the Vee springs arm so as it slides onto the arm behind the brush top and insulates the arm form the brush. On one side that was originally insulated there is normally a push in S shaped small tab Remove existing wire from the tab and solder the decoders Grey wire to the tab and refit it behind the insulation on the Vee spring and the top of the brush. That leaves the now insulated opposite sides brush. Here and if possible obtain form spares suppliers another S shaped tab and solder the decoders Orange wire to that tab then fit it as previously for the other side. However, these S shaped tabs are becoming very hard to find now and even spares suppliers like Peters Spares or Lendons may not have them anymore! If so you will have to very carefully solder the Orange wire to the top portion of the brush - Caution if you've used PVC insulation behind that brush as it will melt if you leave it in place and solder the decoder wire. SO while soldering slide the PVC insulation off, solder and then when cool refit the insulation. Also ensure the soldered decoder wire is not pulling the brush away form the Comm.

Now comes the connections to the decoders Red and Black wires and a lot will depend on how the pick up arrangement is from the wheels. Generally its down to two types.... Some motors have two Phosphor Bronze strips from the wheels one on each side of the motor. If so, solder the Red and Black wires to each of these. Doesn't matter which way around the wires are connected to these strips.
While you have the soldering iron out remove the Capacitor and discard it.
If your motor doesn't have the two Bronze strips but had one wire going to the S tab solder by an inline joint the decoders Red wire to the old wire and cover the joint once cooled with tape or use heat shrink tubing slid on before jointing the two wires. The Decoders Black wire needs to connect tot eh metal of the motor. I would use the screw that is holding the Vee spring in place and wrap the wire under the slacked screw in a clockwise direction then gently tighten the screw trapping the wire

Always test the installation on the Programming track not the main line. Ensure you can change the decoders address number and if correct only then place on the main lines and test its operation.

On older motors like these XO3/XO4 and Ringfield ones too I recommend the use of a "quality" decoder, I would opt for a Lenz Standard minimum or a Zimo.

[scratchbuilt]

Chances are you have reversed one of the axles , or both when cleaning and maintaining. The axles are only insulated on one axle.... common problem when stripping and repairing.