# New Bachmann Mogul smoking (and not from the stack!)



## clairm (Aug 6, 2013)

So, I got the cracked gear replaced and the locomotive put back together and it seemed to run fine upside down on my bench with wires from my MRC power pack dragging on the wheels. I figured it's time to do the R/C conversion. 

I opened the tender and decided the simplest way to power the locomotive would be to just cut the last set of pickup wires in the tender and attach them to my R/C decoder. While I was working on the tender I went ahead and removed the pickup strips from all of the wheels on the tender to get rid of unwanted drag. After getting the decoder wired in, I hooked up my 4 cell LiPo battery that was reading just under 15V, plugged in the 4 wire connector between the tender and locomotive (but not the 2 wire connector), and what do you know, it worked! I carefully turned the locomotive right way up and put some small cardboard boxes underneath it without touching the wheels so I could admire my handiwork and do some more testing. 

I started the locomotive back up and tested to see how little power it look to get the wheels moving. Then I opened the throttle all the way to see how fast it would go. ***POOF***! A huge cloud of smoke puffs out from the cab area of the locomotive! I've smoked some electronics in my day, but I've never seen smoke like this! I dropped the controller and unplugged the battery, assuming that I've blown the motor or electronics or something. I checked to make sure I hadn't accidentally turned on the smoke generator, but the switch is still set firmly to off. After sitting in astonishment for a few minutes, I figured I can't hurt anything worse and hooked the battery back up. Low and behold, the locomotive still seems to work perfectly. The headlight LED comes on when the motor starts moving, the motor goes forward and reverse, but when I open it up at all, again smoke starts wafting up from the back of the locomotive. At this point I noticed that the firebox LEDs glow dimly, even when the locomotive is stopped, which seems strange. I shut everything down for the night.

The question is, have I destroyed my locomotive? How is sending 15V of DC battery power from an R/C decoder directly down the pickup wires different from running on track power???

Clair


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## Curmudgeon (Jan 11, 2008)

Well...first, and just a question....did you unsolder the wires from the driver journal boxes and follow them back to the termination, and remove them fully? 
Next, if you applied power to the loco down the rear light wires, well....on the 4-pin, two are track power (use those), two are backup light. The 2-pin should be the chuff. 
Now, I've seen some of the new ones where they eliminate the backup light wires.....not good... 
There is a junction block fits into a set of slots in the frame just aft of the motor. 
Track wires terminate there. Is it back in the correct place? 
The noise board on the back of the motor...how "new" is the production on this one? 
If it's hosed, and I've had the bi-polar electrolytics...one installed backwards...on the older ones. New ones don't use the big electrolytics. 
Pull the bottom cover, look closely at the terminal block for seating, remove the wires all the way to the journal box tabs. Try it with the loco in the lid of the box, bottom cover held down so you can get it off in a hurry. 
I'd guess misaligned terminal block shorting or noise board. I remove those noise boards...the wires go to the pin on the motor they are closest to. 
TOC


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## TonyWalsham (Jan 2, 2008)

It probably isn't any different. 
However those Moguls have a small pcb on the top of the motor that contains a couple of 47 mfd capacitors for motor "noise" suppression. 
Many of them had these caps soldered in backwards, which means in one direction the caps see reverse polarity and go poof!! after which the magic smoke appears. 

Best thing to do is remove the pcb on the motor and rewire the motor leads direct to the motor terminals.


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## Curmudgeon (Jan 11, 2008)

That's what I said. Mine would go forward, but geez, full throttle for reverse. Shorted the signal right out. 
Those 47uf caps work wonders for smoothing out Phoenix whistles, BTW..... 
I think the newest ones went to the three small, tan 102 caps and two small inductors....but it's been a while. 
We could also have pinched the wires to the chassis between motor and frame. There is a tab on the bottom cover,..I think a similar one on the chassis. If the wires weren't routed around the tab when the motor and gearbox went back in...


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## clairm (Aug 6, 2013)

Yes, I did see the round PCB on the back of the motor when I was fixing the broken gear. I did read some of the other posts talking about removing the noise suppression, but I figured if it ain't broke, don't fix it. Sounds like I should have just removed it when I had the chance.

No, I didn't change any of the other wiring. I am quite sure the wires I tied into are pickup wires, i can trace them through the tender floor, and the other end is tied into a bundle of other wires from the other pickups. I was hoping to install a switch to toggle between track and battery power just in case, so I didn't disconnect any of the pickups in the locomotive.

Hopefully this is just a blown cap on the noise suppression PCB!

Clair


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## clairm (Aug 6, 2013)

Now that you mention it, it did go much faster in one direction than the other! That's what I was trying to figure out when the magic smoke billowed out. Sounds even more like a backwards cap.


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## Curmudgeon (Jan 11, 2008)

Posted By clairm on 27 Aug 2013 10:05 PM 
I figured if it ain't broke, don't fix it.

Clair 

Ah, but it IS broke!
You now have experienced two of the more common issues relating to Bachmann.
There are others, but they may or may not reveal themselves, so we won't discuss them until they show their face, eh?

Pull the board, wires to the PCB go to the pins closest to each wire.

You know....this was a big problem on the 2-8-0's, also. PWM power would really eat them up. I remember one guy who "ran" his in on a PWM power supply and rollers. After a while, got a huge puff of smoke out the stack. The heat generated by that silly board melted the plastic end of the motor out.

Getting Bachmann to allow removal without voiding warranty was one of those fights I eventually won.
I've got stacks of the things. Too small for skeet shooting.
Maybe I can imbed them in resin and make a countertop backsplash for my wife.

TOC


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## clairm (Aug 6, 2013)

Since I'm opening it up again anyway, tell me more about these shims. I understand where they are supposed to go from the excellent picture in the other thread, but I'm unclear on dimensions. It seems like the shims need to be big enough to stay inside the bushings, with a central hole large enough that the axles attached to the wheels pass through them, correct? Otherwise the shims would change the width between the blind drivers.

Clair


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## East Broad Top (Dec 29, 2007)

@ Clair 

Is it this photo and shims you're referring to? 










The shims are just slices of styrene tubing. I think I used the plastic barrel of a Bic pen (the old white style ones) or if not, some appropriately-sized Evergreen styrene tubing I had on hand. I forget the exact diameter. The slices are about 1/32" thick; again, I didn't measure them, I kinda just cut some thin slices by eyeball. 

@TOC, 

You wrote "Those 47uf caps work wonders for smoothing out Phoenix whistles, BTW..... " What do you mean when you say "smoothing out" the whistles? I have an issue with a few of my locos where it seems the directional whistle gets confused as to which way the loco is traveling on occasion. It's not consistent by any means. One of them's the Bachmann C-19 (which I don't think I removed the board from, or if I did, I don't remember doing it), the other's a BBT 2-8-0 chassis, which has none to begin with. My other BBT 2-8-0 chassis locomotive works just fine. Both "quirky" boards are Phoenix P8s, so it could just be the board. Curious to your thoughts. 

Later, 

K


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## Curmudgeon (Jan 11, 2008)

You get the machine-gun sound out of the pnix units when at the limits of range. The whistle seems to be a square wave.....slam on, slam off, where our old Sierras ramped in and ramped out...you could "play" them on the slope. 
The cap just smooths the lead and trail on the pnix units.


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## clairm (Aug 6, 2013)

Back to the shims...

Do the axles from the wheels pass through them, or but up against them like the metal spacer? If the later, wouldn't that change the back-to-back spacing of the drivers? Or is that the whole point of the spacers in the first place?

Clair


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## East Broad Top (Dec 29, 2007)

Clair, the axles pass through them. The idea is simply to limit the lateral play of the axle within the frame so the blind drivers can't wander side to side. 

Dave, I'm confused. The whistles on the Phoenix are digital recordings (as are the Sierra whistles). When you trigger them, they play the three "sections" of the whistle recording--the lead-in, the body (the part that gets held and repeated for as long as you hold the button) and the release. And how would capacitors across the motor leads smooth that out? You've completely lost me... 

Later, 

K


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## clairm (Aug 6, 2013)

That was definitely it! The capacitors were soldered in correctly, but both plastic shells were shrinking from the heat, and the PCB was scorched a bit. Luckily no damage to the motor. While removing the PCB, I took the opportunity to unsolder all the loco pickup wires from the bushings and remove the chuff sensors to clean up the wiring. They will easily be replaced if I need them later. The locomotive now runs wonderfully in both direction, slow or fast. Now to the LHS to get some lube before I burn anything else out!

Thanks for all the help!

Clair


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## Curmudgeon (Jan 11, 2008)

The earlier Phoenix, until they updated the sound files, were slam on, slam off. Try a sierra with radio/battery, and you can play the ramp (long) on it. 
Not so Phoenix...still...even latest software upgrade. 
96 and 97 were worse, as no software updates. 

That's why 100% of my steamers have Sierra.....the Doozie has an old Dallee, removed from something else when upgraded. At least 10 Sierras at a memory count.


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