RailPro > RailPro Specific Help & Discussion

Motherboard replacement - useful or waste of time and $$?

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Alan:
We discussed (guessed?) the keep alive issue with a LM3 in a past post. The LM3 has a ground pin on the connector, not present on LM1 or LM2. The ground pin is what facilitates attaching a conventional keep alive. However, there is a caveat - a keep alive connected across the ground pin and the blue positive wire places a power source, the keep alive, "downstream" from the current overload protection within the LM. This means if there is a short on an output pin and the keep alive is charged then there will be no current protection for the output transistor when the keep alive discharges through the short. Output transistor goes poof, output no longer works.

We speculated Tim may be working on a current regulated/limited version of a keep alive. This approach would spare the output transistors in the event of a short but would also limit drive current to the motor to <100mA (output pin limit). Likely 100mA is more than sufficient for motor drive current in all but a few cases like single locomotive under heavy load.

I'm guessing this current protection dilemma may be the reason it is taking Tim a long time to bring a product to market. If the LM had pins that connect to the output of the internal rectifier (upstream of current protection) then all would be well. That likely entails more change than it sounds like.

Dean:
I looked into adding KA to my RailPro engines. I even bookmarked the link to the wiring diagram posted here. But, to install KA to my RailPro engines would cost almost $500. Instead, I bought a small wire brush and spent an evening repairing and cleaning my layout. I used the small wire brush to clean the outside of switch points and the inside of the stock rails. I made sure the points were being held tight against the stock rails. I gave the track a good cleaning and applied an extra, extra light coating of graphite to the rails.

I have not had an engine drop out in 2-3 months.

I would rather spend my money on more RailPro decoders.  :)

nortoneye:
that was basically TR's point-clean track eliminates the need for KAs.  What did you use to apply graphite?  I have not heard of that before

jim

Dean:
Once I got the rails clean I rubbed a stick of graphite on a one-foot section of track. I did this at various places around the layout. Then I ran a train around the layout to spread the graphite. The idea is to get a microscopic layer of graphite on the rails. I have grades on my layout that are 2% and the trains go up them just fine.
Here is a link to another discussion on graphite. http://cs.trains.com/mrr/f/88/p/267715/3030468.aspx

Another link  http://model-railroad-hobbyist.com/node/17181

nortoneye:
Thanks,  I'll give it a try!

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