LT-52A – KGS Electronics DC-to-DC Regulated Dimmer Power Supply
Available now through the AirParts Aero marketplace.
Overview Section
The KGS Electronics LT-52A is a high-reliability, pulse-width modulated (PWM) DC-to-DC Regulated Converter, specifically engineered to act as a precision dimmer power supply for aircraft instrument lighting. It transforms an unregulated 28VDC aircraft bus voltage into a regulated, adjustable 0–5VDC output.
Primarily used in Textron Aviation (Cessna and Beechcraft) aircraft, the LT-52A is designed to control the intensity of incandescent bulbs across the cockpit pedestal, instrument panel, and overhead consoles. Unlike traditional rheostats that generate excessive heat by dissipating energy, the LT-52A uses efficient PWM technology to provide smooth, flicker-free dimming while maintaining a compact and lightweight footprint.
Key Features Section
High Efficiency PWM Design: Utilizes pulse-width modulation to minimize heat generation, boasting approximately 77% efficiency at full load.
Precision Voltage Regulation: Maintains a steady output within 2% for line, load, and temperature variations, ensuring consistent light levels regardless of engine RPM or battery state.
Remote Rheostat Control: Designed to be controlled via a remote 5K Ohm, 1/2 Watt potentiometer, allowing for flexible cockpit installation.
Advanced Protection Circuitry: * Overvoltage: Output is limited to approximately 125% of the rating, even if the remote rheostat fails or shorts.
Overload: Features pulsed current protection if the load exceeds 125% of its 10-amp capacity.
TSO-C71 Recognized: Meets FAA Technical Standard Order (TSO) requirements for airborne power converters.
Internal Trim Pot: Allows technicians to set the maximum output voltage ceiling for specific fleet requirements.
Technical Specifications Section
| Specification | Detail |
| Manufacturer | KGS Electronics |
| Model Number | LT-52A |
| Part Number (Textron) | LT52A |
| Input Voltage | 20 to 40 VDC (28 VDC Nominal) |
| Output Voltage | 0 to 5 VDC (Adjustable) |
| Output Current | 10.0 Amps (Continuous) |
| Max Power Rating | 50 Watts (VA) |
| Mating Connector | KPT-06A-14-5S (or equivalent) |
| Dimensions | 2.3" H x 2.3" W x 5.8" L |
| Weight | 1.5 lbs (683 grams) |
| Service Ceiling | 55,000 Feet |
Aircraft Compatibility Section
The LT-52A is a standard OEM component for many Textron Aviation airframes:
Beechcraft King Air (90, 200, 300, 350): Used extensively for instrument panel and sub-panel lighting control.
Cessna Citation Series (500, 525, 550, 560): Found in the cockpit lighting dimming circuits for various flight deck configurations.
Beechcraft Baron & Bonanza: Often used in 28V electrical systems to provide 5V dimming for avionics backlighting.
Hawker 800/900XP: Integrated into the cabin and cockpit illumination control systems.
Technical Applications & Safety
The LT-52A is essential for night flight operations, where the ability to dim instrument lights to a very low level is critical for maintaining the pilot's night vision.
Safety Warning: Ensure adequate cooling. While the LT-52A is highly efficient, it can still generate heat when driving a full 10-amp load of incandescent bulbs. At an ambient temperature of 71^C, sufficient airflow is required to prevent thermal shutdown. Additionally, if the lights begin to "pulse" or flicker, it is often an indication that the unit is in Overload Protection mode, suggesting a short circuit in the lighting bus or too many bulbs connected to a single unit.
Technical Engineering Insight
The engineering value of the LT-52A lies in its Positive Logic Overvoltage Protection. In many cheaper converters, a component failure can result in the full 28V input "shunting" directly to the 5V output, which would instantly blow every bulb on the instrument panel. The LT-52A is designed with a "failsafe" clamp that limits the output to roughly 6.25 V (125% of rating) regardless of internal failure modes.15 This protection of the aircraft's lighting assets makes it a preferred choice for Part 25 certified jets where cockpit darkness during a night approach is a significant safety hazard.
Installation & Maintenance Addendum
Potentiometer Wiring: Use high-quality shielded wire for the Pin D (Remote Control) circuit to prevent electromagnetic interference (EMI) from inducing "flicker" in the lighting.
Pin Cleanliness: The LT-52A uses a circular PT-02E-14-5P receptacle.16 Ensure the pins are free of oxidation; high resistance at the output pins can lead to localized heating and connector melting at high current draws.
Bench Testing: When testing, use a 5K Ohm rheostat to verify the full 0–5V swing.17 If the unit only outputs 0V or a fixed 5V, the internal logic or the external control circuit has likely failed.