Large Scale Central

New K-27 Chuff Board

Electronics
#1

I posted this on the Bachmann forum and thought it would be useful if I posted it on LSC as well.

The K-27 was the first Bachmann large scale locomotive with the plug and play socket. The chuff circuit in this locomotive was designed with a chuff that goes positive to indicate a chuff. While some sound boards work fine with this design, most prefer a chuff circuit that goes to ground to indicate a chuff. This required the end user to install a transister and often a capasitor in the tender to allow the chuff to work properly. All Bachmann locomotives with the socket since then have a chuff to ground circuit.

My wife and I have a large outdoor railroad with several Bachmann K-27 and together with some of our operating crew designed a replacement PCB-5 chuff circuit board that incorporates both protection circuits as well as a chuff to ground design. For a limited time we will be offering these replacement boards for $30 each plus actuall discounted shipping. Note: We do not intend to produce these as a product going forward, this is a one time offering.

PXL_20260406_212507047
PXL_20260406_2125070471588×1856 266 KB

This circuit board is a direct replacement for the origional PCB-5 circuit board that sits right behind the motor in the K27.

In the above photo, the board on right is the origional Bachmann PCB-5 circuit board. The board on the left is the newly designed K-27 PCB-5 circuit board.

If you are interested please send me a note.

Stan

#2

If you use a Phoenix does it still have the issue? I’ve not torn into mine as of yet?

#3

Mickey

Unfortunately yes. We have several Bachmann k-27s with Phoenix sound. Some only required a user instaled transistor while others required a transistor with capasitor. In addition if you plug in the tender while the track is powered there is a rick of damaging the optical sensors.

The replacement board we developed is based on the C-19 circuit and solves both of these issues.
Unsoldering the wires from the old board and resoldering these to the new board are required. The pads on the new board are a little larger making this a little easier to perform.

Stan

Old Board
Old Board1920×3413 623 KB

New Board
New Board1920×3413 454 KB

Stan

#4

Sign me up for one. PM me details. Thanks.

#5

Stan, will this board work with a K fitted with a Rodney Edington gear reduction?

#6

Bob

The new board is a direct replacement of the existing board so it will fit with Rodney’s gear reduction.
Its going to be a little more work as the motor will be directly over the board and likely will have to be removed in order to get to the screws holding the board in place.

Next week I will be converting a K that has Rodney’s gearbox installed and after this conversion I will be able to tell you what extra steps will be required.

Stan

#7

I have one of his conversions. i believe i removed the motor/gearbox at the cover plate on the axle.

otherwise no issues.

AL P.