Installing a sound decoder in Non Dcc ready K4

[uncbob]

Does anybody know if the motor is is isolated  in the Bachmann PRR K4 NON DCC ready engines

I want to put one in and have the engine unplugged the tender open when it dawned on me that the motor might not be isolated

I don't want to open up the engine so I sure hope it is

PS the color coding in the tender leaves much to be desired

[Tom M.]

Bob,

I want to give you a qualified maybe.  I've added sound to one of these locos, but there were a couple of different production runs and I don't know when your loco was produced.  If it is the older style that employs the split frame design, the motor is not isolated.  Here is a link to the TCS site's installation pictures showing this loco.  While this is for a non-sound installation, you can get an idea of what you need to do to isolate the motor.

http://www.tcsdcc.com/public_html/Customer_Content/Installation_Pictures/HO_Scale/Bachmann/K4_Pacific_4-6-2/bachman_n_scale_k4_pacific_4_6_2.htm

Because of the color coding concerns you mentioned, I don't see how you are going to avoid opening the loco.  You will need to trace each wire to ensure it is actually connected to the point you think it is.  If the motor and track pickup wires get crossed, you run the risk of "toasting" the decoder.  I never rely on Bachmann's color coding because they do not always comply with the NMRA wire color standard.

However, if you truly want to avoid taking the loco apart, I suggest you first install an inexpensive non-sound decoder as a test.  If the loco runs and the decoder doesn't go "poof" then you know the motor is isolated and the wiring/color coding is correct.  Better to find this out on a $15 basic decoder than a $100 sound decoder.

Again, I always take the time to physically trace the wiring and test it with a multi-meter.  That's the only way to conclusively know the wiring is proper before installing and powering-up the decoder.

Good luck,

Tom

[richg]

Get you multimeter out an do a continuity check.

Rich

[uncbob]

Thanks for the info

[Jerrys HO]

Bob

From my understanding, DCC ready meant it is ready for decoder install whether it be plug or hard wired and the motor should be isolated already. Other's can chime in if I am misunderstanding ready vs. onboard. I was under the assumption loco's were made DCC ready so you could install the decoder of your liking without going through the trouble of isolating everything.
Hope my understanding is correct because that is something I would like to do in the future.

Jerry

[richg]

Are there any wires between the loco and tender?
With nothing connected to the motor connections,
use a 9 volt battery and two wires to connect the battery to the motor. Connect the wires and see which combination turns the drivers so the loco would be going forward. Find out which motor terminal the positive of the battery connect to. Mark it with a red paint dot. Many DCC locos today will have a similar mark to denote what is the positive terminal for the orange decoder lead.
Follow the NMRA DCC wiring code.

Looks like you will have to drill holes in the botom of the tender for a 28mm speaker. That is the standard size for many  HO steamers that I have seen.

RIch

[richg]

From the link I saw in the message, you will need six wires between the loco and tender.
Two for the motor.
Two for the headlight.
Two for pickup power from the loco.
Apparently there are wires in the tender from your message. How many?

Rich

[uncbob]

I agree on the wires
The main question is is the motor isolated
I guess using an ohm meter on the 2 engine wires and reading each against the frame should tell me
I know which are the engine wires if  I assume the light is the 2 wire plug

I forgot to show this

http://bandb3536.com/meo/pcboard.jpg

[richg]

That is a DCC ready loco from what I see. Probably first generation from the looks of the PC board and the motor should be isolated. When you said wires in the tender, I suspected as much.
You can see the DC adapter that you remove and plug in the 8 pin decoder which would mean the motor is isolated.
This all assumes the loco is for this particular tender and has the matching connectors.
I have said many times here, a picture is worth a thousand words.

Th single resistor might be for for dimming the headlight in reverse. Might be 120 ohms.
The capacitors "might" be under the PC board or in the loco right on the motor.

Rich

[richg]

More thoughts. You will have to remove the weight and drill holes for the speaker. No idea on how much spece between the PC board and rear of the speaker, or do a complete hard wire with no PC board.
Put a thin bead of bath caulk around the rim of the speaker and keep the caulk off the cone.
Figure out how to add weight after all the decoder install is done.

Rich

[uncbob]

Doesn't  look like any DC ready board that I have ever seen
Of course you say first generation
Are you saying that small brown Bakelite piece  with the two big solder blobs comes out and a socket is underneath

[uncbob]

Here is what I think the leads are
Sure isn't NMRA color coding

http://bandb3536.com/PRR/pcboard2.jpg

[Tom M.]

Yes, if you remove the plug in the middle of the board you should find an 8 pin NMRA-style socket underneath.  In theory, you could simply wire the sound decoder to an 8-pin plug and plug it into the socket.

However, if I was going to install a decoder in this loco I would hard wire it.  You should be able to trace and identify each wire by how/what it is attached to on the board.  You simply need to unsolder each wire from the board (one by one) and solder it to the appropriate corresponding decoder wire color.  Cover each solder joint with shrink tubing.  The existing board is very crude and there is no telling what components on it could conflict with the Tsunami's circuitry.

If the loco uses LEDs for lighting, you will need to install a resistor on both the white and yellow wires to reduce the current going to the LEDs.  A value between 780 and 1K ohms will work well.  If the loco uses 12v bulbs for lighting, no resistors are required.

An alternative to cutting holes in the tender floor for the speaker would be to mount it facing upward under the coal bunker.  Then you need to use a pin vise with a #78 drill bit to drill dozens of holes in the coal load to allow the sound to escape.  I did this on a K4 for one of my clients.  I drilled the holes in the "cracks" between the lumps of coal.  I tended to do this at the intersections of lines and this tended to make the holes less visible.  If you do mount the speaker to the floor, you can mount the existing weight on top of the speaker enclosure using doublesided foam tape to secure it.

Good luck,

Tom

[Tom M.]

Yes, I tend to agree with your wiring identification.  In theory, the red track pickup wire should trace to the right rail (+) and the black to the left rail (-).  You will need to determine the positive and negative motor connections.  Otherwise, the loco's physical direction of travel and lighting will not match the indicated direction on your DCC throttle.  The same is true for the lighting if the loco uses an LED.  Of course, you have a 50/50 chance of being right so worst case you will simply need to reverse the orientation of the wires if the loco travels in the wrong direction or the LED won't light.

Tom

[uncbob]

Tom
Thanks
I agree that is what I will do

I was confused as to whether it was an isolated motor
Happy to hear it was


It is easy to see the power pickups as to left and right ( can't believe Bachmann used motor red to tender black and motor black to tender red

Any way of knowing whether the light is LED or Bulb

BTW I did install a sound decoder in my Bachmann 2-8-4 but that was DCC ready and color coding was correct
I did burn out the LEDs though--replaced and did add resistors