The Mystery of Electronics

[jonathan]

Some time ago I picked up a P2K SD7 B&O #1830 at a train show.  Nice Loco.  A year later I picked up another P2K SD7 B&O #1829 at another train show.  What luck!  I can double-head these engines. Great! Only the #1829 runs at exactly twice the speed of the #1830.  Surely somebody is trying to have some fun with me.  I am pulling the shells off to have a look at the circuit boards.  Please tell me there is a resistor somewhere I can bypass. 

The gears in both locos seem to be the same sizes.  I can hear the motor in the faster locomotive is also running faster than the slower locomotive.  Each day, the call to the dark side is getting louder.

Regards,

Jonathan

[digitalgriffin]

Until recently Proto was switching the final gear ratios with every release.  I believe they finally settled on 18:1.

Is this a DCC ready, or DCC installed engine?

[jonathan]

DG

Both engines are dcc ready (paperwork says so). 

Interesting about the gear ratios.  I just looked at the gears.  I didn't pull them out and count teeth. 

The newer one (guessing, based on when I purchased) is the faster locomotive (#1829).

Jonathan

[HO-Ron]

I don't think that you will see any difference in the motor gears. The difference will be, if any, in the truck gears. Pop the truck gear cover and compare the two. My thinking is you will find one or more the gears to be different.
Speed gearing is in the trucks for most every diesel engine. If you have to, count the teeth. 
Good luck!!

[jonathan]

Thanks, guys. 

I'll bet your right.  Something tells me I have two nice locos that I will never be able to double-head until I switch to you know what.  At least each is  strong enough to pull a twenty-car train all by its lonesome.

Regards,

Jonathan

[Atlantic Central]

What color boxes did they come in? If one is blue and the other silver, they might well be geared differently. The silver boxes are the newer ones and some models did recieve some changes about then. Were they new or used? One could have a bad motor.

Are you sure one does not have a decoder installed by some previous owner? A dula mode decoder would run dramaticly differently on DC than a regular DC loco.

Sheldon

[NarrowMinded]

If your a long way from going dcc why not add a resistor to slow the first unit down? 

NM

[rich1998]

If your a long way from going dcc why not add a resistor to slow the first unit down? 

NM

If you go this route, calculate the wattage needed for the resistor. The resistor could get kind of hot. Even then, this could be iffy.

Lex

[NarrowMinded]

I forgot about turning all that extra energy into heat, it would likely be a pain to get the right resistor to match the speed anyway.

If it's not the gearing of the units then it could be the motors are differant, maybe one has more windings then the other which would  make it run at a differant rpm on the same voltage.

just my 1.5 cents

NM

[pdlethbridge]

and I was beginning to wonder about the subject of this thread.

[BillD53A]

There is no mystery involved with electronics.  All electronic components contain magic smoke, which makes them operate.  The key to working with electronics is to NOT let the smoke out.
Someone may have let the smoke out of one of your engines.

[jonathan]

Wow.  You have given me some real food for thought.

Just to clarify:  both engines were bought new and have no decoders.  Both came in the silver boxes.  However, the slower engine came in the larger silver box, where I was required to assemble the shell to the frame.  The faster locomotive came in a smaller silver box; the shell was already attached to the frame.

The gears all appear to be the same size, but I haven't counted teeth.

I have been pretty lucky, in that all my new loco purchases, to date, have had no real problems.  Murphy could have finally caught up to me, and just maybe I have a bad motor in the slower engine.  Strange though, it pulls just as well as the faster engine, just a lot slower. 

I appreciate all the great suggestions.  I think I'll have to pull apart the slower engine, test the motor and other parts, and see if I can't find some logical reason for its behavior.  Could be it was made that way on purpose.  These motors "appear" to be the same ones that Athearn uses.  I do happen to have a new Athearn motor I put in an old GP35.  Would be happy to sacrifice the Geep if the new motor will fit.  Wouldn't that be something...

Regards,

Jonathan

[pdlethbridge]

It could be as simple as adjusting the tension of the brushes. A brush may be too tight, or too loose. Lengthening or shortening the spring pushing the brush to the commutator could make a world of difference. While powering the motor, ( out of the engine ) play with a spring and see if adding or decreasing pressure speeds up the motor

[jonathan]

PD:

This makes sense.  When the shells were off both locos, the slower loco's motor was running at slower rpms with the same amount of current applied to both.  I figured if it were a gear difference, the motors would be at the same rpms, given the same amount of current.

These engines are nice runners.  I was hoping to avoid a complete disassembly, on the chances I might break something.  However, it is going to be necessary to take the engine to nearly parade rest, in order to get at the motor. 

I will be extra careful.  Never worked on a Proto before.  There are more wires and little extra pieces than other locos it seems.  I will check and mark the circuit board, so all the little wire connections go back where they belong when I'm done.

Thanks a million.

Jonathan

[jonathan]

After breaking down, monkeying with, and putting back together the slower locomotive,  I cracked open the faster locomotive.

This is why I named this thread after mysterious electronics.

The first shot is the board on the slow loco:



Here is the fast loco board:


Holy cow! What is that weird thing on the left?  I find if I disconnect it, the engine no longer runs.

So I've got two identical engines, mechanically speaking,  but their wiring is totally different.  Who knew?

Thanks for reading.  I'm still learning I guess.

Regards,

Jonathan

PS Electronics are INDEED mysterious... especially when I hear about things like "magic smoke" .