Convert New K4 to DC

[BoyREB]

Mark, that did it! Thanks for the second post.  I was afraid to continue to pry off the shell for fear of breaking something.  Pulling the chassis forward unlocked the rear tabs.  Decoder unplugged easily.  Female-socket blanking plug-in board (pre-wired) is on it's way from Tony's Train Exchange thanks to Eric one of their technicians and his persistence.  I'll post an  update when it arrives.

[BoyREB]

The plug arrived from Tony's yesterday and as promised I am posting the results.  The plug they sent was supposed to be a female but in fact it is a male shrouded in a guide making it look like a female.  The pin spacing is close but not exact, so no joy in Mudville.  I'll keep trying and post if any new news.
Bob

[spookshow]

It'd be helpful to know which pins on the tender PC Board need to be jumpered for DC operations. Bachmann didn't provide that information in the instructions, but I assume it's an NMRA standard and is documented someplace.

Cheers,
-Mark

[BoyREB]

Thanks Mark,
I used the diagram that came with the locomotive (back page - lower left corner).  I jumpered pins 2 & 3 and pins 8 & 7 using little PC option jumper pins and voila! It runs nicely.  Now if I can find out if the headlight has the current limiting resistor incorporated to the little PCB in the front of the engine as shown in your excellent write up on your Spookshow page or will I have to add one in my little jumper config.
Bob
P.S. You might get a kick out of a project Hans Starmans did for me using one of my old Aurora Trix (yes an original Trix postage stamp trains - I saved it in the box since 1969 because it ran like c**p).  We converted it to a L1 using the K4 shell and the mechanism from a Kato Mikado.  It runs like a dream and pulls well.

[spookshow]

Good grief, I must be blind - I totally missed that diagram in the instructions.

I'll take a picture of the LED board and post it.

Cheers,
-Mark

[BoyREB]

I changed the jumper plugs to a couple of plug connectors I got from Hong Cong that are exact pin fits.  I ordered a bunch them for my signals so they would be plugable and had some extras.  I'll send a picture or so to help any other wayward DC souls like me and if anyone wants to do the same thing, I'll post where I got them.  BTW, the engine now runs like a good DC runner but still needs some break in - running on my test oval now.  I see where the  funny "hitching" came from in DCC mode - there is a slight "bind" at slow speed - I hope a after a "break-in" period it will work out . .  More importantly though, where is the headlight LED current limiting resistor?  I called Bachmann and am awaiting a reply.  Thanks for everyone's help.
Bob 

[spookshow]

Does this help?



Incidentally, thanks for trailblazing this. I'm sure there are many who will be walking this path.

Cheers,
-Mark

[BoyREB]

Looks like 4 blobs of solder, three wires and a surface mount LED - no resistor (unless it too is surface mount and hidden under one of the wires covering the bottom (in the picture) part of the LED trace but I don't think so.  I'll add a 470 ohm resistor to my little jumper configuration and connect the headlight wire (pin 4) through it to the minus jumper.  I'll let you all know how things work out later this afternoon.
Bob

[spookshow]

Nope, just the four wires and the LED. So, you think the resistor is on the decoder and not on the tender PC board?

Thanks,
-Mark

[BoyREB]

 As far as getting the headlight to work via straight DC, I'm still not sure where the LED current limiting resistor is.  This is what I have managed to find out though. Pin 2 on main PCB plug goes to pin 6 on the engine plug and then to point R on the headlight LED board. Pin 3 on the main PCB plug goes to pin 5 on the engine plug and then to motor +. Pin 4 & 6 on the main PCB plug goes to circuitry on the PCB (possibly the electrical noise reduction circuitry). Pin 5 on the main PCB plug goes to pin 4 on the engine plug and then on to the + point on the LED PCB.  It is still a mystery because it is listed as "+3.3V B+ Common".  My guess is it is power to the DCC board. I may have to isolate Pin 3 on the engine plug from the main PCB as it goes to the - point on the LED PCB but I don't know where it goes to on the main PCB and I can't see the trace.  Pin 7 on the main PCB goes to pin 2 on the engine plug and then on to motor -.  Pin 8 on the main PCB plug goes to pin 1 on the engine plug and then on to the L point on the LED PCB. My next step is to insert a 1K resistor in the engine plug pin 3 circuit. I'll post the results (and whatever else I discover along the way).

[BoyREB]

As promised, I am posting the results of my straight DC conversion plug efforts and directional headlight quest.  It is now working on my test oval with my pulsed DC throttle.  I was able to achieve almost all of my objective (which was to come up with a plugable connector that allows an easy swap between straight DC and the original DCC decoder).  A minor exception is that I had to solder a tiny wire to the solder pad of the pin 4 engine plug receptacle on the main PCB.  I could have soldered a mail pin from my connectors and then the whole adapter would be instantly swappable but it's running and I don't want to mess with success.  So in conclusion, pins 2,3 & 5 on the main PCB need to be jumpered together.  Piins 7 & 8 on the main PCB need to be jumpered together and a current limiting resistor (I used a 1K ohm) needs to be connected to that jumper (I soldered it) and then the other end of the resistor needs to be connected to the pin 4 addition to the engine connector plug.  I would recommend the connector pin approach to keep everything plugable.  One note though.  The pins on the engine plug are numbered in reverse from the Main PCB numbering from the wiring diagram that comes with the engine.  If you position the engine so the PCB lines up with the diagram, the engine plug (on the right) pins are numbered bottom to top., so pin 4 is the 4th one up from the bottom.  Good luck all!   

[spookshow]

A picture or two would be great!  

Cheers,
-Mark

[BoyREB]

OK I took some pictures.  They are not as good as Mark's but should be good enough to give everyone an idea of what the mods look like.  One change since the last post.  I decided to add the pin to the #4 engine plug solder pad on the main PCB so the whole modification is pluggable for easy backward compatibility ...or forward compatibility depending on your perspective :-) .  I also took a picture of the diagram with my mods and the jumpers I used. Using the lowest resolution on my camera, I was able to get the pictures down to 212kb - still way to large to attach here.  Any suggestions would be helpful as I've never posted pictures before.

[Hunt]

OK I took some pictures.   . .  .  I also took a picture of the diagram with my mods and the jumpers I used. Using the lowest resolution on my camera, I was able to get the pictures down to 212kb - still way to large to attach here.  Any suggestions would be helpful as I've never posted pictures before.

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[spookshow]

Thanks, Bob. Here's your picture -



For future reference, I also added your picture and instructions to my review page -

http://www.spookshow.net/loco/bachk4.html

Cheers,
-Mark