O Gauge Circuit Breakers

Tranz4mr.com

Littleton Colorado

O-Gauge Circuit Breakers

Modern O-Gauge 3 rail and S-Gauge 2 rail trains that operate on AC voltage have electronic boards that are sensitive to voltage spikes and over current events caused by derailments. These events can zap expensive circuit boards which are getting hard to find and difficult for most to repair. This page will show some of the choices and options currently available to mitigate these issues.

Here are some important items to consider:

Speed - How fast is the response time?
Resettable - Do I want to Manually Reset or Auto Reset?
Is the current trip level fixed or selectable?
What trip level do I need? In this case a ammeter to measure current would help.
Cost. Will I need 1 power zone or 6 zones?
Ease of Installation and setup?
Ease of use?

Is my modern transformer or brick with built in protection good enough?

Cicuit Breakers:

Circuit Breakers provide over current protection.

Here are the most commonly recommended fast-acting 5A circuit breakers that pair well with the 1.5KE36CA TVS diode for protecting modern 3 rail O Gauge and 2 rail S Gauge trains.

Top Recommended Options

DCC Specialties PSXX-AC Intelligent Circuit Breaker.(SKU: DSPPSXXAC) This is often considered the best overall for modern setups. It’s a solid-state intelligent breaker with built-in current limiting, very fast response (milliseconds), adjustable trip current (including ~4–6A settings), auto or manual reset, and built-in TVS/transorb spike protection on both input and output. Great for AC 3-rail systems. Pair it with an external 1.5KE36CA at the transformer for layered protection. Available from Tony’s Trains, Iron Planet Hobbies, etc. (around $80–$100).
TinMan3Rail “Gunrunner” Circuit Breaker Kits (5A versions) These are ultra-fast acting breakers specifically marketed for Lionel/MTH to protect against shorts and derails. Available as single or dual-loop kits. Many users report they trip almost instantly compared to original Lionel breakers. Good value and easy to install.
Lionel 6-14178 and 6-34120 are electronic fast-acting breakers built into a convenient lock-on style housing. They were designed by Lionel specifically to protect TMCC/Legacy electronics from shorts and spikes when using PowerHouse supplies. They offer automatic reset and are fairly fast, but they are not quite as advanced as the PSXX-AC (no active current limiting and less robust spike protection).
Henning’s Trains 5A Self-Resetting Breaker Compact, quick-trip, auto-resetting breaker designed for Lionel transformers and modern electronics. Simple to add between the transformer and track. Popular for its small size and reliability.

Quick Advice

For most modern consists, 5A is a good starting point per output/channel. Adjust higher (6–8A) if you run multiple engines or heavy loads to avoid nuisance trips.
Best setup: Fast breaker in series on the hot/center-rail side + 1.5KE36CA TVS across the output (parallel).
Fastest & Smartest: PSXX-AC (current limiting makes it very effective at protecting sensitive boards).
Best value fast option: TinMan Gunrunner Kit.
Easiest plug-and-play: Lionel 6-34120 or 6-14178 (especially if you use FasTrack).

All options work best when paired with 1.5KE36CA TVS diodes placed sparingly (1–2 per power district max if running DCS) to avoid signal degradation.

Quick Comparison Table

Breaker Option	Type	Trip Speed Characteristics	Reset Method	Current Rating	Built-in Spike Protection	Approx. Price	Pros / Cons for Modern Lionel Use
DCC Specialties PSXX-AC	Solid-state + current limiting	Fastest overall: ~12–15 ms trip with active current limiting before full trip. Lowest energy let-through.	Selectable Auto or Manual	Adjustable 1–10 A	Yes (TVS on input & output)	$80–$100	Best protection for Legacy/TMCC/DCS boards. Smartest and most effective. Higher cost.
TinMan3Rail Gunrunner Kit	Fast magnetic-style	Very fast – "Almost instant" on shorts/derails. Significantly quicker than stock Lionel breakers.	Manual reset	~6 A per loop	None (use with 1.5KE36CA)	~$25 (dual)	Excellent speed/value. Popular recommendation. Manual reset.
Lionel 6-34120 (TMCC Direct Lockon)	Electronic / Solid-state	Fast electronic trip – Described as "instant" or "fast acting" on shorts and derailments. Designed specifically to protect TMCC/Legacy electronics.	Automatic self-reset	Selectable (135W / 180W mode, ~7–10A range)	Some (limited)	$60–$70	Official Lionel solution. Easy track connection + LED indicators. Not as sophisticated as PSXX-AC.
Lionel 6-14178 (TMCC Direct Lockon)	Electronic / Solid-state	Fast electronic trip – Very similar performance to the 6-34120. Provides quick over-current protection.	Automatic self-reset	Selectable (135W / 180W)	Some (limited)	~$40	Same family as 6-34120. Good for PowerHouse supplies. Slightly lower price point.
Eaton FAZ-B5/1-SP (B-curve)	Thermal-Magnetic	Fast magnetic trip on hard shorts (3–5× current). Good response but slower than solid-state on moderate faults.	Manual reset	5 A	None	$15–$25	Reliable industrial-grade. DIN-rail mount.
Airpax / Sensata IEG6 or Snapak "instant"	Hydraulic-Magnetic	Very fast on high overloads (some "zero delay" versions trip in <0.1 sec at high currents).	Manual reset	5 A typical	None	$20–$40	Temperature stable and fast. Choose "instant" curve for best speed.
Henning's Trains 5A	Thermal self-resetting	Moderately fast thermal trip – Better than old Lionel breakers but slower than magnetic or electronic types.	Automatic self-reset	5 A	None	~$8	Cheap and convenient. Not ideal if maximum speed is needed.
Qualtek QLB-053-00DNN-3BA (5A)	Thermal	Slow-to-moderate thermal trip (several seconds at moderate overload).	Push-to-reset	5 A	None	$5–$10	Inexpensive but slower reaction.
TE Connectivity W57 series (e.g. W57-XB7A4A10-5)	Thermal	Slow thermal trip (often 4–40 seconds at 200% overload).	Push-to-reset	5 A	None	$5–$12	Basic only. Not recommended for fast protection.