WIRING ON HEAVY MOUNTAIN 4-8-2

[WayneH]

HI,

I have recently obtained a Spectrum Heavy Mountain 4-8-2 code number 82501 second hand.  It runs fine on DC.  In trying to get into the tender to convert to DCC I disconnected the wheel sets as the tender cover did not seem to come loose with just the one screw being undone. I am not too sure if I reversed the wheels or not on refitting. It appears that the red wire coming into the tender is connected to the right hand side of the loco and i have checked that the non insulated tender wheels connected to the red wire in the tender (the front tender set)are also on that side.  I have also checked that rear tender wheels are opposite to the front ones as far as insulation is concerened.  I have run the loco on DC and it works since i reconnected everything but it will not run with a DCC chip in it and it shorts the controller.

I have tested continuity on the loco and i do get a reading of about 66ohms between the right and left wheels when i assumed there would be an infinite reading. I have also tested continuity betweeen the wheels on the loco and tender and i am salt getting readings of about 66ohms.  I'm wheels on the same side i am getting readings fo about 6ohm.

Is there a wiring diagram available for the loco and tender as the instruction sheet does not have anything in it on wiring.


On the 8 pin socket in the tender it appears that pin8 is marked although the number by the pin may not be supposed to be the PIN number.  IN fact if i assume that is pin 8 with the blanking pin in the loco does not move on DC but if i assume it is pin 4 it does move.  Not sure if that is relevant or not.
Regards

Wayne

[trainman203]

Well, if the engine runs fine in DC but shorts out with a decoder (what you call a "chip"),  it's pretty clear that there is a polarity reversal issue of some kind with the decoder and/or its installation.  I'm not going to go any further than that because I've never done a decoder install but from what you're saying, that seems to be where you need to be looking.

Whatever brand of decoder you're using, you probably should call Customer Service at that vendor and talk to them about your problem.

If you have a sound decoder, you could try just placing the tender on the track alone and see if you can activate the sounds without a short, which would further tell you that the problem is not with the decoder or the tender installation, but somehow in the connection between the engine and the tender.

[VTBob]

The heavy & the Light Mountain DC / DCC versions had an 8pin plug in the tender. If you push too hard to install the decoder plug, the boad will touch the steel weights, causing a dead short. Also, it'll cause a dead short if you have it plugged it backwards. The #1 pin is not clearly marked on these & will cause issues exactly what you are describing.

I recently just repaired about 4 of these things for pretty much the same problem you are describing. In all the board was touching the metal weight & the plugs were installed backwards. You can use electrical tape on the weights to stop the short issues, & after you've done this, leave the tender shell off when you install your decoder. Test to see if it is shorting out. Then if it is, pull the 8pin out, flip around 180 & reinstall it - the problem should correct itself.

Good luck with the fixings.

R. Montanye
Montanye Models

[VTBob]

Also -- a tender color photo can be found from the parts dept website :

https://estore.bachmanntrains.com/images/ho_parts/0AD01-PCB02.JPG

Red in the front, black in the rear.


R. Montanye
Montanye Models

[WayneH]

Hi Guys,

Thanks for your assistance on this.  I will check those items.  A member of my model rail club also suggested that in the loco itself there may be a direct connection between the power pick upos on the wheels and the motor.  Does anyone know if this is true.  I was assuming that the pick ups in the loco fed into the PCb in the tender and that from there to the motor.  He suggested dthis might be why i am getting the continuity reading between the loco wheels.

[VTBob]

If you remove the trailing truck on the locomotive, you will see a small pcb board with 2 copper tabs. These are the drive wheel pickups. HOWEVER - if your locomotive runs fine on straight DC power, the problem is the board in the tender. Double check the orientation of the 8pin decoder.

I just remotored one for a customer & had to dismantle the entire thing. So many tiny screws to get it apart. I have some pictures of it, but no way to get them on here.

R. Montanye
Montanye Models

[trainman203]

I hope you get that engine fixed.  The light and heavy mountains were beautiful early spectrum offerings that had the best of everything the spectrum line offered, myriad separately applied details in particular.  If there was a flaw with those engines, it was the downward pointing driver pick up wipers that if bent downward wrongly the slightest amount, could snag on track work.

I don't expect those two engines to be ever be re-introduced.  Although they could get around 18 inch radius curves, it was an awkward experience.  The current mikado appears to have replaced these engines for good, slightly shorter and able to get around 18 inch radius better, plus they got rid of 90% of the seperately applied details which brought the price point way down a fair amount.  The mikado is still a nice locomotive, I have several, overall performance is exceptional, including radically slow switching speed

So, be careful with that beautiful engine, you may find it difficult to get a a second chance with an additional one.