H Class decoder and motor fried.

[Brew Man]

Good morning

Yesterday I decided to take the lid off my Wainwright H class loco as it wasn't quite seated properly. I managed to tuck the decoder into the small compartment in the side tanks and the body went back on snugly.

Testing it on the track soon produced plumes of smoke through the chimney. Looked great but very short lived disappointed_relieved. I'm afraid the decoder and motor are stuffed. Well I know the decoder is as I have tested it. Pretty sure the motor is too. Looking at the H class service sheet the motor is listed as X7170, however it only lists it for models R3538/39 and 40. My model is R3631 which it doesn't mention. Can anyone confirm whether or not the X7170 will fit my model please? I'm guessing it will but would like to be sure before buying one. I've messaged Hornby but from previous experience I could be waiting a while for a response.

Thanks for any help received.

Decoder-wise, I'll be fitting a DP2X-UK as I think it will be a much better fit than the normal 8 pin wired types.

[Bulleidboy]

Good morning to you.

The DP2X-UK fits perfectly - no messing around with the harness. My H-Class is not currently on the layout, but having fitted the decoder and snipped off the capacitor, it ran perfectly for forty five minutes in each direction on the rolling-road.

[Going Spare]

I think the only reason your locomotive is not shown specifically on the Service Sheet is that the sheet is now over 4 years old and because of the vast number of new locomotives that are being introduced, Hornby simply have not managed to keep the updating up-to-date.

Dealers offering the replacement motor are not restricting its usage but, to be safe, I would query its suitability when you place the order.

[Brew Man]

@BB

That's good to know, thanks.

@GS

Thanks, I did message the supplier that I'd identified and they knew as much as me. I'm waiting to hear back from Hornby, might actually give them a ring as it will likely be quicker.

Thanks both.

[Brew Man]

Follow up:

Just spoken to Hornby and have had confirmation that the X7170 will fit my model, so have just ordered one.

A good outcome.

[ColinB]

I would be surprised if the motor has gone bang, when a decoder fries it gives off tons of smoke. The only thing is that perhaps the motor went short circuit taking the decoder with it, but that is rare. Are you sure one of the stray wires didn't touch the chassis, that normally fries them.

[Brew Man]

I'm pretty sure. I replaced the blanking plate and tried to run it DC but it didn't respond except a few bright sparks from around where the brushes are located, then nothing. I'll know more when I take it out. If it is repairable it'll do as a spare. The new one is only costing just over £13, so worth the expense IMO.

[ColinB]

Check the capacitor across the motor, I have had them go short circuit before now.

[Brew Man]

Good tip, thanks. Will probably take it out completely when I replace the motor.

[Fishmanoz]

Yes, no need to check it, just chuck it.

[Brew Man]

So I've just put a new motor in this, and - nothing sweat. It's not working either with a new decoder or in DC mode. I know the motor is working, checks out OK with DC applied direct to the brushes. I'm wondering if any of the insulation on one or more of the wired has melted and shorted to an adjacent wire when the original decoder cooked

Does anyone have a schematic of the DCC socket wiring by any chance? I seem to recall Rob having something relating to one in a previous thread. I'm getting continuity between pins 1 and 5 with the blanking plate plugged in which doesn't seem right.

[Chrissaf]

Does anyone have a schematic of the DCC socket wiring by any chance?

 

 

Basic generic schematic for NEM652 DCC socket. LED directional lighting is optional.

[ColinB]

Here is the simple test I do. With a multimeter check resistance between adjacent pins, they should all read high impedance except between pins 1 and 5. Amazingly I have measured values ranging from 10 ohms to 100 ohms between pins 1 and 5, which is effectively the motor resistance (10 ohms seems very low, but the motor worked). Next put the loco on the track and check pins 4 and 8 go to the track. Now check that pins 1 or 5 are not connected to the track by measuring the impedance/resistance. I suspect in your case one of the motor wires has fell off, probably touching the chassis as it did it. That would smoke the decoder.

[Brew Man]

OK, chaps, thanks for that, I'll do some checks.

[Brew Man]

Update:

Problem solved. The pick up wires from pin 8 had gone O/C. That is, they were still soldered onto the PCB but the solder point was not connecting with the pin. I'm thinking a short piece of track might have blown when the decoder cooked.

It's likely that the original motor is still in tact - haven't tested it yet, but I now have a spare.

Thanks for the help and advice, Colin and Chris.

[ColinB]

If the 8 pin pcb was one of those early Hornby ones I am not surprised. They seem to incredibly difficult to solder to, and when you do you have to be so careful that the solder doesn't splash over to the next pad. Also the pins on the socket don't always seem to make contact even though you know you soldered them. Then if by chance you leave the soldering iron on the pad for too long you either lift the track or the individual socket falls out. I am pleased to say the new ones from Hornby which they released in the last year, are tons better.