NW-2 board

[mmagliaro]

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

I agree, a drop-in replacement is obviously the easiest way to fix this.
Thank you, but no, I wouldn't really have any use for that board.

[Joetrain59]

Just off the phone with Bacmann. No parts available for the NW-2. Looks like it's Jeff to the rescue.
 Thanks Max, Peteski, and Chris for input.
 Joe D

[Upstate Gator]

@jeffstri If you can share pix or recommendations after upgrading the board, it might be useful to several of us. I have a 44-ton and a Doodlebug to upgrade at some point.
Ben

[peteski]

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.

Well, none of the fuses or circuit breakers trip instantly at (or slightly above) their rated holding current. Even the old-fashioned fast-blow fuses will not go poof at the rated current (whatever is imprinted on their case).  This (pdf) document has some info on standard fuses and how much overcurrent and time will take for them to blow.  Solid state breakers are often thermal devices so they must get warmed up to trip.

[mmagliaro]

Well, I learned something today.   Thanks Peteski.   I thought the fast-acting glass fuses blew much quicker and at much
closer to their rated current than they do.   They still need150% to 200% of their rated current going through them
for several seconds before they blow!  (and most of them have 200% overload hold times of more like minutes, not seconds!)

What that means is that your motor better be able to handle a serious overload for a long time without
cooking because the overload devices aren't going to save it. 
This is particularly disturbing for coreless motors because they have no big iron in their armatures and they heat
up very fast under overload.   It would be a race to see which device, the motor or the fuse, blows first.  I'm betting it's the motor.

[peteski]

To be honest Max, I don't know how much thought the engineers who designed that model (or any model which has the solid-state breaker in the motor circuit) have put into this.  It might as well be like the old saying goes that the device which is begin protected by the fuse will burn up first, protecting the fuse from blowing. 

This might be one of those things where the engineers thought was a good idea, but totally useless in real life.  The breaker also has some internal resistance - that will also reduce some of the voltage supplied to the motor.

Just this week I have seen a Minitrix loco produced in early 2000s where one of those solid-state breakers is being utilized, even though that loco uses one of the old-fashioned 3-pole motors with conventional iron-core armature.  I have no idea why.  Those motors can take serious overloads without getting damaged.