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Discussion Starter #1
Hi Folks

http://www.bachmanntrains.com/home-usa/k-27/page3.html



Just up on the Bachmann site is wiring for the K27 but no diagram.

My main interest is to fit a 2.2K Phoenix sound system and at first reading it is a mess.

It looks easier to rip out the boards and fit magnets on the wheels.

On DC the lights stay on so look as if they are direct wired but I will get my loco on Saturday and the extra weights tht are "not" required so may find more info.

Is the boards used for anything in the DC mode or a waste of space.

I might have to ask he who should not be named.
Frustrated Dave
 

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I know the feeling

Maybe this will help;

First is a schematic. This is based on hours of tracing out the circuits. Bachmann has a similar one, but it has a couple errors, and this one lays out the circuits in a way that makes them a little easier to understand. I've had a few friends check this one and it seems to be correct.

Click on the drawing to load a bigger one.







Second, here is a corrected interconnection drawing based on the one that should have been included with you Kay. I only included enough parts of the loco to identify the board locations. I corrected some glaring errors in the wiring, and color coded the drawing to match the actual colors of the wires.



You can click on this small drawing to download a larger one.





Dave has covered may of the things you might want to improve on the Kay. However, He runs battery power. If you want to run the Kay on DC, there are some other things to consider;



Bachmann's drawing shows a pair wire connections between the tender front and rear trucks. They don't exist. Look at my drawing and you will see that if the left wheels of the trar truck ore on opposit polarity  track from the front track, the there will be a direct short between the front and rear truck. IE. as in when you split a turnout. the entire maximum current of you power supply will then travel from the rear truck to the circuit board, through the lands of the board and out the front of the board to the front truck. If you are using something like a 15 amp pack, expect to buy a replacement board. I recomend a little upgrade, cut the wires from the rear truck right where they enter the rear of the circuit board, extend the wires and splice them into the wires coming from the front truck. While you are at it, examine how the wires going through the floor of the tender to the trucks, have to go through emall holes in a METAL bolster. The holes need to be enlarged, the sharp edges smothed, and some extra heat shrink added so the wires don't chafe the insulation and short out on curves.



Now look at the wiring of the loco. 



Here is a real challange. This is for fun, the first correct answer wins.



Trace the path of the electricity entering the loco on the RIGHT front driver. Follow it through the front pickup brush board, second pickup board, etc all the way to the dummy plug, and then back through the loco  through the motor, and then all the way back to the LEFT front driver. When doing this, count each time the circuit ENTERS a circuit board. 



Now.

 

HOW MANY TIMES DID THE MOTOR CURRENT GO THROUGH A CIRCUIT BOARD?

A [  ]  9 times

B [  ]  13 times

C [  ]  22 times



For extra credit:

How many times did the motor current have to go through a connector pin?



Another fun piece of trivia. The current going throug the motor by entering the front left driver and exiting the front right driver travels through over 6 feet of wire.





Of course, the answers to those questions are things you might want to consider if you expect plan to make any improvements to your Kay.



B0B
 

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Discussion Starter #3
Hi Bob
WOW
Did the disigner get paid per wire board and plug talk about overkill especialy for DC or batt power.

I am not going to but would like to rip it all out and hard wire it with just two wires to the tender to carry the current for the multiple contacts.

Loco LEDS could be hard wired with resistor and diode same with tender all switches could go (Has anybody ever used the NMRA switch) cab light switch on engine.

Sound worked from tender wheels or if you really need to from the drivers WOW up to four wires now much more reliable and better engineering than that load of connections

Has anybody written up sorting it out for DC or battery

Many thanks Dave
 

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Posted By David Buckingham on 04/08/2008 1:22 AM
Hi Bob
WOW
Did the disigner get paid per wire board and plug talk about overkill especialy for DC or batt power.
I am not going to but would like to rip it all out and hard wire it with just two wires to the tender to carry the current for the multiple contacts.
Loco LEDS could be hard wired with resistor and diode same with tender all switches could go (Has anybody ever used the NMRA switch) cab light switch on engine.
Sound worked from tender wheels or if you really need to from the drivers WOW up to four wires now much more reliable and better engineering than that load of connections
Has anybody written up sorting it out for DC or battery
Many thanks Dave




Thanks for the schematic as well Bob, I always love to look at these things to see what electronics are being designed into engines today.

Dave -

Were there no instructions with that loco that explained what the various options and switches are for?

If you really want to fiddle with the wiring, for DC track operation only you could get rid of SW1 and SW2 and hard wire the right and left rail directly to the DCC connector.
SW1 selects between battery and track power, SW2 switches polarity (remember, LGB decided that with the right rail negative, engines would move in a forward direction, for all the other scales, it's just the opposite)

The cab light switch lets you control the cab light either via a DCC decoder if you use one or you have the option of turning the cab light on or off manually in DC mode. Same idea for the marker lights. If you want those lights on all the time, you can certainly get rid of those two switches and wire the ground directly. The smoke unit switch works the same way.

As to wiring LEDs with just a resistor and diode, that would be a step backwards. The little two transistor circuit around each LED is a constant current source. That means that the LEDs will be at the same brightness no matter what the track voltage. This is actually a feature that buys you something when you run the loco on DC and is not really required for DCC since the track voltage with DCC is pretty much fixed.

Getting back to the original question about sound. You can pick up the chuff trigger on pin 5 of the connector, there is a jumper JP1 that allows you to either keep or remove a second chuff trigger. I assume the two optical sensors for the chuff trigger are set up 90 degrees out of phase so that you have the selection between ywo or four chuffs per revolution.

I didn't look at the wiring diagram, only at the schematic; the schematic is a good solid commercial design - very little wrong with it.
It nicely accomodates track, battery and DCC power.

Regards, Knut
 

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Posted By krs on 04/28/2008 11:58 PM
Posted By David Buckingham on 04/08/2008 1:22 AM
Hi Bob
WOW
Did the disigner get paid per wire board and plug talk about overkill especialy for DC or batt power.
I am not going to but would like to rip it all out and hard wire it with just two wires to the tender to carry the current for the multiple contacts.
Loco LEDS could be hard wired with resistor and diode same with tender all switches could go (Has anybody ever used the NMRA switch) cab light switch on engine.
Sound worked from tender wheels or if you really need to from the drivers WOW up to four wires now much more reliable and better engineering than that load of connections
Has anybody written up sorting it out for DC or battery
Many thanks Dave

Thanks for the schematic as well Bob, I always love to look at these things to see what electronics are being designed into engines today.
Dave -
Were there no instructions with that loco that explained what the various options and switches are for?
If you really want to fiddle with the wiring, for DC track operation only you could get rid of SW1 and SW2 and hard wire the right and left rail directly to the DCC connector.
SW1 selects between battery and track power, SW2 switches polarity (remember, LGB decided that with the right rail negative, engines would move in a forward direction, for all the other scales, it's just the opposite)
The cab light switch lets you control the cab light either via a DCC decoder if you use one or you have the option of turning the cab light on or off manually in DC mode. Same idea for the marker lights. If you want those lights on all the time, you can certainly get rid of those two switches and wire the ground directly. The smoke unit switch works the same way.
As to wiring LEDs with just a resistor and diode, that would be a step backwards. The little two transistor circuit around each LED is a constant current source. That means that the LEDs will be at the same brightness no matter what the track voltage. This is actually a feature that buys you something when you run the loco on DC and is not really required for DCC since the track voltage with DCC is pretty much fixed.
Getting back to the original question about sound. You can pick up the chuff trigger on pin 5 of the connector, there is a jumper JP1 that allows you to either keep or remove a second chuff trigger. I assume the two optical sensors for the chuff trigger are set up 90 degrees out of phase so that you have the selection between ywo or four chuffs per revolution.
I didn't look at the wiring diagram, only at the schematic; the schematic is a good solid commercial design - very little wrong with it.
It nicely accomodates track, battery and DCC power.
Regards, Knut

Really?
REALLY?
So, the little surface-mount, non-repairable by the normal hobbyist current control transistors are a step backwards?
Since using those A) eliminates the use of incandescent bulbs, and B) from what I understand, kills transponding, how exactly is that backwards to make it actually work?
On the chuff, you have actually tried to get the chuff to work?
You talk about the jumper, but do you really know what it does?
This engine has about 4 circuit boards too many, a whole handful of feet of useless wiring, chuff that doesn't work unless you, the hobbyist, performs some surgery and grafting, and if you want properly colored incandescent bulbs, you get to bypass at least half the top firebox board, re-wire the smokebox board, rip the Ames Super Socket With Integrated Production Electronics out, fix your counterweights, wonder at your gear ratio and current draw on grades with a load, puzzle over the phantom squeaks from the loco on curves, find out someone has seemingly thrown in some new prototype wheel profile, with a different flange angle than Bachmann seems to have used before, with a fillet that, instead of being curved, looks to be a box-section, like they ran the lathe tool almost all the way down the flange, and almost all the way across the tire.......and what we seem to have is scale flange squeal....
There is a reason I do what I do when re-working these.
Utilizing unnecessary electronics and connectors is asking for future problems.
 

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Four that are pointless.
The rest I can use parts of or simply ignore (like chuff boards).
 

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8 more reasons not to spend money on the k27, or at least be satisfied just to take out of box and run it the way it comes!!!!!!
 
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