You might look at NTE series 59 breakers such as this: https://www.frys.com/product/1965566?site=sr:SEARCH:MAIN_RSLT_PG. They're available from 0.25 amps on up.
MRC transformers are almost bulletproof and cheap on Ebay
Henry
COB Potomac & Northern
Shenandoah Valley
to the Model Railroader forums. Your first few posts will be delayed by the site moderators, but that ends pretty quickly. I hope you stick with us and become a regular contributor.
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The easiest solution is to wire a low current draw 12 volt lamp in series with the tracks. That way if the rails short out, the lamp just comes on very bright, and no overload takes place. That is really a stone-age solution, but it still works.
Also, please get a better power supply! That is something you will never regret.
-Kevin
Living the dream.
I recently installed a small DC HO layout in a local library. Today I discovered one of the cheap Life Like 390j transformers I am using was not functioning at all. It stopped functioning after a derailment on the track it was connected to. I assumed that they had circuit breakers built in but I guess I was wrong. I replaced it with a spare 390j but was wondering if there was a circuit breaker or fuse I could install between the track and the transformer to keep from destroying too many more of them. Any recommendations would be appreciated.