NW-2 board

[mmagliaro]

Max, you got the wiring right. The loco does run hood forward, but not cab end reverse.. Really have no need for decoder, but want to keep lights.
 Thanks. Checked Marks review, it is a can motor.
 Joe D

It is a coreless can motor, whose supply voltage is unknown because it is normally driven by the outputs of that decoder.  So it could theoretically be almost anything from a 1.5v to a 12v motor.   Since you are able to run it forward (on DC I assume), and nothing bad has happened to it, I'll just go ahead and assume that it
will be okay on 12v.

After seeing how complicated that board is,  I would like to ask you to take some much closer, super-macro photos of it.  It is very hard to really see where those traces are going, especially around the LEDs.
I think if it were me, I would be inclined to actually snip leads on those little ICs and remove them from the board instead of trying to cut traces  (the two surface-mount 8-pin ones and the bigger one labaled "U1").  And then I would run very fine jumper wires between the truck power pads (the solder pads where either pair of truck black wires goes) to where the motor leads are soldered to that board.  That should get the motor going in forward and reverse.  Then I would start thinking about the headlight and taillight LEDs.

[Joetrain59]

Hi Max, hope these photos help.

[peteski]

On the top of the top photo (near the copper clip) and on the bottom of last photo I see a burned copper traces on the PC board.  Those are some of the areas from where you released the magic smoke.

Since the PC board is double-sided, you need to also take same type of photos of the other side.

[mmagliaro]

Joe,

That does help.... sort of.

For one thing, I can now clearly see two badly burned traces on the board (probably happened when the decoder
got fried).  At this point, nothing on that board can really be trusted.

As a first "hail mary", I would repair the two burned traces, and see if the whole thing works.
But my guess is that components got destroyed when those traces burned.  Still, you never know.  You might
get lucky.  (I wouldn't try it for very long....  touch some power to it and if the motor doesn't run, quit while you're ahead.
Those traces may have burned because something else is shorted and they might just burn through again somewhere else).

If that doesn't help anything then, I would go with my original plan.  Assume the board is toast and just remove
components and wire-bypass everything.

Get rid of the 3 surface mount chips, since you're not going to use them anyway,
and they might cause problems if they are internally destroyed.
Then, I would jumper power to the motor leads as shown, and fix those two burned traces.

If you can do that, and get the motor to run in both directions on track power, we'll move on the headlight and taillight LEDs.

[Chris333]

There is another burn next to the red wire attachment.

[Joetrain59]

Thanks. All this, because I did not see NW-2 parts on Bmann site. First thing I'll do is take pix of other side, as Peteski suggests. Also noticed a chaffed wire from front truck. Don't know if it was always there, or it happened when putting shell back on months ago.
 Joe D

[Joetrain59]

2 photos of top of board;





 I always noticed the red wire from cab LED's was flimsy at board. Now I know why.

Joe D

[mmagliaro]

Well, one thing I see.... at the left of the board in your new photos, there is a 12k SMD resistor (marked "123").

It is R20 and C9 is above it.  It looks like if you were to jumper some +v to the right-hand terminal on C9, that
would light the LED (i.e. R20 and C9 are the dropping resistor and a smoothing cap for the LED).

But unfortunately, 12k is going to be really high for driving this off DC track power.   The LED will be pretty dim until the
engine is moving fast.  On DCC, when there was a full 12v there all the time, I'm sure it worked great.
What all this means is that you will need to put your own resistor in there, more like a 2k rather than 12k.

Sooooo.... now we're into changing some components to make the LEDs work nicely.

Joe, if your soldering skills are up to it, you can certainly do this.  But if you are nervous, I think you may want to send
me a PM about fixing that board up for you.

[peteski]

To me it seems like the 1.5K resistors R8 and R9 are the current limiters for the LEDs.  They are close to what looks like 8-pin function output devices marked 403MP. The capacitor and the 12K resistors close to the LEDs seem to be some sort of anti-flicker circuit (maybe).  You're right, this is getting a bit complicated. 

Also, on the latest photos there is another exposed trace. It is right above the mounting hole with R22 legend right under the hole.  Looks like the mounting screw scraped off the green mask and was touching the bare copper of the trace.  I suppose if the metal chassis in insulated that it is no big deal, but I still don't like that.

Now, on an unrelated rant, I wish that the PC board designers used a san-serif typeface for the legends (like Helvatica). It is much clearer and easier to read.

[mmagliaro]

R8, I can see... I am having a hard time following the traces from R9 in the photos.

Joe, if it were me, I think I'd be cutting the traces into and out of R8 and R9, then jumpering a wire from +v to them,
and then jumping a wire directly out of the other side of them over to the LEDs (and cutting any traces that go to the LEDs.

Yep... this board is very crowded and complicated, and it isn't worth trying to make sure everything is cut or repaired.
I would cut traces around the components I want to re-use, just so that I can re-use them, and then jumper new wires
right through.    If you get rid of the chips, there will be plenty of room to play around on that board with small wires,
neatly fastened down so it will be reliable and won't be suffering from broken wires.

I repeat, if you want me to just patch that board up and get the motor and LEDs running, send me a PM.

[peteski]

Max, if you take this on I would recommend keeping the over-current protector (solid-state circuit breaker) in the motor circuit.  That is the large SMD component marked W 020 (the copper clip is on it in one of the photos).  I suppose that the RFI suppression stuff (chokes and few caps) could stay too.  Either way works.

[Joetrain59]

I have done successful soldering with SMD components, but not usually on a board. (Changing out 3mm LED's on some older loco's with some SMD resistors, caps, and diodes from Ngineering.) I don't think my eyes are up to this work, nor the complexity of it. As a last chance, I will call Bmann to confirm is replacements are available. Swapping out the board I can do.(?) Otherwise, I'll PM Max.

Everything get's better, but more complicated, from cars to appliances, and everything else.
 Thanks.
 Joe D

[jeffstri]

Joe, I just bought an NW-2 yesterday. The Bachmann decoder works fine for what it is but I'm going to replace it with one that has more functionality. PM me if you're still interested.

I also have Bachmann decoders for the S4, GE-70Ton, 2-10-2, and 4-8-2 heavy mountain if anyone is interested.

Jeff

[mmagliaro]

Max, if you take this on I would recommend keeping the over-current protector (solid-state circuit breaker) in the motor circuit.  That is the large SMD component marked W 020 (the copper clip is on it in one of the photos).  I suppose that the RFI suppression stuff (chokes and few caps) could stay too.  Either way works.

Thanks for that tip, man.  I didn't know that's what that was.   I haven't had any luck looking it up.  What's the current
rating on it?  Does "020" imply something like 200 mA ?
But yes, if I end up fixing this one, I'll definitely keep that thing in the current path to the motor.


/////// edit //////////
I have found the info on these (since I posted the first part of this entry)...

It is apparently a 100mA "hold" rating.
BTW, has anyone ever actually looked at the specs on these resettable solid-state overcurrent devices (like Raychem's
or Littlefuse, etc).  The specs are really awful.   Hold at 100mA, but trip at 300 mA.   300 ???
Sorry, but if I want to limit the current to 100 mA, I can't have this thing only being guaranteed to shut
off when the current hits 3 times that limit.   The trip times in the spec also say that it takes
 1.5 seconds to trip at 500 mA !
After 1.5 seconds at 1/2 amp, you can just forget it if the thing you are trying to protect is a coreless motor.
It will be "delicately browned"  by then.

I remember seeing these kinds of ratings years ago when these devices first came out.  I'm sad to
see that they really haven't improved.  It's almost like having no protection at all.

[Joetrain59]

Well, Jeff seems to have come up the most viable solution for now. Let me contact him, as his is brand new, to see what it looks like. Max, if I get a replacement board, do you want my current one, just for sh&^s and giggles?
 Joe D