tomcat,
The basic answer: It depends on the model. Space, age, and decoder needs/wants all play a role in choice.
I have done locomotive installs both ways, board replacement (Atlas silver and older Atlas/Kato "yellow box" units), and hardwired "chip" installs (On older Bachmann Spectrum, BLI Blueline, and Athearn BB units.) I have also used a variety of brands. (Digitrax, both chip and board replacement, Soundtraxx, and ESU boards.)
Both require soldering, do not rely on the slip on tabs for board replacements.
And, as mentioned, just because a unit came with a board, does not mean you must use a board replacement. (Although, if you do use a board replacement decoder, make sure it is the right brand replacement. They are [somewhat] easier though not always the best choice.)
Ricky W.
HO scale Proto-freelancer.
My Railroad rules:
1: It's my railroad, my rules.
2: It's for having fun and enjoyment.
3: Any objections, consult above rules.
Hi, Tomcat
I recall my first decoder installs some twelve years ago and I do remember being somewhat overwhelmed and intimidated by this new technology and back then there wasn't all the choices DCCers are given today.
I began with the easy picken's, the larger HO Life-Like E-7 & 8s, the Stewart (Bowser) F-3, F-7 and FTs. Once the shell was off it was pretty easy to see what my options were. I soon figured out that I couldn't rely on factory color coding, in some cases all the wires were black. For some reason Life-Like was prone to make the motor+ a black wire and the motor— a red wire. Some of my early installs I had to chande the NDOT (normal direction of travel) in the CV programming since I had the motor wires reversed!
I think many here will agree that it is usually best practice to remove the original PC board which is loaded with capacitors, voltage regulators and diodes for headlight effects in DC. In Bachmann's case there is also a radio interference circuit in the motor wiring that's best eliminated. It plays havoc on some decoder BEMF sensitivity.
As manufacturers saw the "future" of DCC they made attempts at making their engines DCC "ready" by including plugs and sockets but some of these attempts were lame. Life-Like had a routine where you had to saw traces off the PC board! "Cut Here for DCC" was printed in several places on the board.
David, of course, has good advice and one thing I'll add here is that you will hear talk of "motor isolation". Some locos will use the frame as part of the electrical circuit to the motor. This is a sure way to toast a decoder if any part of the rail wiring comes in contact with the motor wiring after your install. Most early Athearn engines use a motor contact in the bottom of the frame that has to be isolated. One or two of the Life-Like switchers were like this, too. Kapton tape comes in handy for this isolation and you will have to solder an additional motor lead in place (remove the brush clip first).
As far as the "shape" of the decoder, many families of decoders come in several different "form factors" for instance this TCS is called an A-series:
http://www.tcsdcc.com/Customer_Content/Products/Decoders/HO-Scale/A-Series/A-Series.htm
It IS a PC board and it is a convenient, easy replacement for Athearn, Atlas, Kato and others. It simplifies installation and it clips on to existing tabs on the motor to hold it in place.
Do you have to use that board in an Athearn engine? Not at all. You can get any one of dozens of "hard wire" decoders that only have wire leads and you can install it by soldering directly to the locomotive's wiring (get familiar with small heat-shrink tubing) and you have the same DCC characteristics as the board type.
Sound decoders now come in several "form factors" as well. ESU Loksound has a micro sound decoder that piggy-backs on to a PC board like the A series above and the new WOWsound decoders come in both board form or pig-tail wires.
http://www.esu.eu/en/start/
If you do a Google search with your locomotive model and add "DCC install" to the search you may find lots of information on how to choose and install your decoder.
There are also sites like Tony's Train Exchange and Streamlined Backshop Service that have decoder install info.
http://tonystrains.com/category/tonys-tips/decoders-and-installations/
http://www.sbs4dcc.com/
Hope this helps,
Good Luck, Ed
Hi all wise ones
I have been wanting to start doing my own dcoder installations. I do have the relevant skills to solder but I have one problem to overcome.
Can someone explain to me why there are engines with a board in them, which you can plug in a decoder (8-21 pin) and there are some with just a chip wired straight to the lights and pick ups.
I feel confident enough to install a decoder myself but how do I choose what type of decoder goes in what engine?
When do I need to put the board type in an engine or just wire a chip in them?
Am I right thinking that the board type are more for sound installation?
Please help.