I'm wanting to install a new DZ143 decoder on an older Bachmann Spectrum GE Dash 8-40C. While researching this idea, I found one blog where someone did this and had smoke spewing within a few seconds of applying power. He resorted to using Bachmanns decoder. This gives me a little pause, so I thought I'd ask around for help and ideas. These photos show the side of the frame as well as the top and bottom of the default PCB. If anyone has insight into this process, I will appreciate the help offered. Thanks in advance, Thanks :sly: Mozarelli Sent from my Xoom using Tapatalk 4
How is the original PCB held in place to the frame? Frame to PCB connections, motor to PCB? Does it look like this one? http://www.tcsdcc.com/public_html/C...nn/Spectrum SD-45/Bachmann_Spectrum_SD-45.htm If so just hook up the wires from the decoder and solder them to the original PCB where the jumper clips are. Of course remove the jumper clips first!
Thank you for your reply. That image is close, but not exactly what I have. The one you posted appears to be a newer PCB and different loco - SD-45 compared to my SD-40. However. The connections between the PCB , the frame, and the motor appear to be the same for both. My main concern is the forum post linked here: http://www.bachmanntrains.com/home-usa/board/index.php?action=profile;u=1547;sa=showPosts In particular, Post Number 4 says something about jerking and smoke and also mentions components on the PCB getting hot. I saw another post somewhere that said I should remove the large, brown capacitor across the motor wipers. This capacitor exists on the PCB you linked to above, but is not present on my older PCB. Do you (or anybody) know if I need to add or remove any components on the PCB before or after soldering the decoder to the PCB? Thanks again! Sent from my Xoom using Tapatalk 4
I would remove the chokes (L1 and L2). The capacitor I believe is labeled C3 and is a surface mount type capacitor. you will have to check this out to see if the connections are across the motor termanials. Hard to see in the photos.
woodone, If I my research is accurate, L1 and L2 are 4.7 Ohm 1/2W 10% resistors. Why they are labeled "L" instead of "R", I can't say - unless "L" stands for LOAD. It looks like L1 resists current flow between Pin 1 on the decoder and the upper motor wiper (Fireman's/Left side?) while L2 resists current between decoder pin 5 and the lower motor wiper (Engineer's/Right side?). If this is correct, it makes sense that removing them is fine as long as the decoder appropriately handles current flow to the motor - which is kinda the whole point to a decoder, right? Another benefit to removing these two resistors is that it gives me the room I need to place the DZ143 without having to mill the frame. Mozarelli I'll do some circuit and component testing and let you know what I find. Sent from my Xoom using Tapatalk 4
I still think that the L1 and L2 are chokes (inductors) has they have color code bands just like resistors. See here;http://www.elexp.com/t_induct.htm
woodone, I guess it's been too long since my EE classes! To an electronics rookie like me, anything that looks like a resistor must be a resistor. You're right about them being inductors - hence the "L" next to the devices on the PCB. I'm guessing they either filter noise, or more likely, store current to prevent jerky starts and stops. Do you know which service they provide and if my DZ143 decoder will replace or obviate those services? Mozarelli Sent from my Xoom using Tapatalk 4
In my installs I have removed these chokes. Noise reduction? Don't know why they are used in Bachmann DC locomotives. If removed you will have a bit more room for a decoder.
