Motor suddenly started running very jumpy. Video attached. We’ve cleaned everything and it seems like an electronic issue. IMG_2135.mov (11,750kb) downloaded 86 time(s).

No, the motor is at the back of the loco.

Hi John
What to check?
- first, check if it is not a current pick-up issue: place the loco upside down and power it using 2 wires one on the slider and one on the chassis. If the motor turns smoothly, then you have a pick-up issue EITHER the slider is bad OR the wheel bearings are dirty In this case a tiny drop of oil on the bearings, let the loco run for a while and wipe the excess of oil.
- remove the brushes and check them for wear and cleanliness, clean the brush guide with a piece of cleenex and tweezers (we call them Bruxelles over here)
- without brushes the motor should turn freely through a gentle rotation of the wheels. If not, unscrew the brush holder and position it so that the rotation is free before tightening (not too much as it is plastic). This is because during the large time span of production of this model, lack of precision could cause the rotor to collide with the inductor.
- for a big repair check the motor impedence in various rotor position (it should be around 40 Ω ish) but if the value is 10 Ω ish, then the rotor is burned and needs changing before it burns the decoder as a result (personal experience). Another symptom of this burned winding is the motor does not always starts (needs help in some positions)
- another possible test: disconnect the motor and power it with DC voltage (5 VDC to 9 VDC) and see if the rotation is smooth with a small current (under 100 mA)

Cheers
Jean

It is common to refer to a loco as a tender in opposition to what we call a tank loco, which was much more common in Europe.

I assume that is the reason for calling his loco a BR50 Tender.

Sorry guys, yes, I said tender just because I wanted to describe the model a bit more (it’s not a tank engine). This model has the pickup and decoder in the coal tender and the motor obviously in the loco.

I have checked and cleaned the motor and brushes and everything runs smoothly when it’s apart and a little more friction but still smooth when the brushes back in and the motor is back together. There was a little binding happening at one point (I think maybe the main rods / connecting rods were misaligned). That is fixed now but I’m concerned that this could have burned the motor (I don’t see any evidence of that).

I’m going to check the impedance. Anything else I should check?