The reason the decoders usually don't fry is that most shorts are between the rails. The short is before the decoder. As stated earlier the problem comes in when the motor isn't completely isolated from the frame. Non isolated motors will fry more times than not. It's a learning curve but you'll be fine.
Springfield PA
Fear Not!!
"Convert my son......."
I have converted around seven brass steamers to DCC so far, no dead decoders and very few issues with shorts in general. My biggest issue is improving electrical pick -up in small brass to keep it creepy. This is an issue in good old DC as well. I have installed lots of tender truck pick-ups as well as trying to cram big stay alive caps in tenders.
My buddies, who some of whom have huge brass collections, are in the process of decoderizing their fleets one loco at a time. One of these guys is in HOn3 and has converted at least 25 of his brass locos to sound DCC over the past year or two.. He has some hair-raising tales about cramming micro TSU's into C-16s....
There are several web articles on the process. google Mark Schutzer for a start. Good luck with the project.
Guy
see stuff at: the Willoughby Line Site
WHile all this is true, I would caution that it depends on how the motor is isolated, and even diesels aren;t immune to this - the Proto 2000 Alco S1's in particular. The motor is isolated when you remve the dummy plug to install a decoder - however one side of the motor is grounded to the frame and it IS possible that the trucks could turn enough in the case of a derailment to contact the frame, resulting in that decoder-popping cross between the power input (red and black) and the motor drive (orange and grey). The solution for that one is to install a new orange wire to the lower motor terminal so it is no longer connected to the frame.
Similarly, with ANY loco, if you make sure that neither brush is connected to the frame, even if it is isolated from the track pickups, you will indeed never have a problem where a derailment would bring together those wires which should never touch.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
steamnut,This is no chance to fry a decoder due to a simple short of a wheel hitting a the frame or any other kind of short like that. Once you bolt the loco back together and the loco, headlight, etc., works, then it's fine. Sure, a decoder can go "bad" on you and loose it's memory or die, but that's due to the decoder's design and the reality of modern solid state electronics. It wouldn't matter if it was brass or plastic in that case.
I have several brass locos of all kinds (steam, diesel, electric, self-powered passenger cars), and I've got a DCC decoder in all of them. I am also in a model railroad club that has many brass locos that have been decodered. Not one of them has had a fried decoder due to a short.
The worst one I did was my NJ/Custom Brass NH I-4 4-6-2 with a DC70 open frame motor. It has a DH121 decoder in the cab (not known for reliability). I once had a short where the trailing truck derailed and got caught in a switch on my club's DCC layout. The breaker didn't trip due to the high resistance of the short. When I picked up my loco I could smell something hot, and when I looked I saw that the centering spring on the trailing truck was glowing red. When it cooled off, I touched the spring and it disintegrated. Now that's a pretty bad short. That was over 5 years ago, and I still run that loco with the same decoder in it today.
What will pop a decoder is a short between the headlight leads (white, yellow and blue) and the energized frame, or crossing the red/black with the orange/gray wires. As long as that doesn't happen, I don't know how one would every pop a decoder by way of a short circuit.
Paul A. Cutler III
Folks, I am currently operating a dual-mode control system. I have a roster of about 30 diesels that I am about 2/3rds of the way through converting to DCC, and when I operate in "diesel mode" I use DCC.
I also have a larger stable of steam locomotives, mostly brass. I so far have not converted any of them to DCC although three of them already had DCC when I purchased them.
I'm of two minds as to my path forward. (BTW I have an excellent memory-walk-around conventional-DC throttle system). On the one hand the "freedom" of DCC is of course appealing. In particular when I'm double-heading my steam, which is pretty much the normal modus aperandi, the 0-5-0 "pusher from the heavens" is the only realistic means of mating the two DC-powered steamers. But my concern is actually NOT about the cost of the conversion (I'm not a money-bags, but due to the time involved it would be spread over at least a couple of years, probably about 2 decoders a month), but instead about short circuits. Those of you have have had experience with brass will know that its almost impossible to totally prevent momentary shorts with many brass steam models. My key question is: would a momentary short of that type fry a decoder?
If, as I think, the answer is "yes" then converting my brass fleet will be an exerscie in futility.
I look forward to opinions and even more so, to any voices of experience.