DS3800DSFC1A - System Firing Daughter Card

SPECIFICATIONS:

Part Number: DS3800DSFC1A
Manufacturer: General Electric
Series: Mark IV
Product Type: System Firing Daughter Card
Connector Type: 28-pin edge connector
Logic Type: TTL
Operating Temperature: -40 �C to +85 �C
Board Size: 16.51 cm high x 17.8 cm
Repair: 3-7 Days
Country of Origin: USA
Availability: In Stock
Status: Discontinued by Manufacturer

FUNCTIONAL DESCRIPTION:

DS3800DSFC1A is a System Firing Daughter Card manufactured and designed by General Electric as part of the Mark IV Series used in Speedtronic control systems. It is an essential interface module in GE Speedtronic Mark IV turbine control systems, responsible for managing ignition and fuel sequencing signals. It conditions and buffers logic-level inputs from the main firing board using TTL circuitry, implements digital sequencing logic for coordinated turbine startup, ignition, and shutdown, and provides LED indicators for real-time status monitoring. The card connects to the main firing board via a 28-pin connector, facilitating bi-directional signal communication and integration of interlocks and auxiliary firing outputs. Protection elements, including current-limiting resistors, clamping diodes, and transient suppression circuits, safeguard the board against voltage spikes and shorts. Operating on a nominal +5V TTL supply, with logic high 2.4V and logic low 0.8V, and propagation delays typically under 200 ns per gate stage, it ensures accurate, safe, and reliable firing sequences under all industrial operating conditions.

OPERATION:

The card conditions and buffers signals through TTL circuitry, ensuring proper voltage levels and signal integrity for downstream firing circuits. It then applies digital sequencing logic to coordinate the timing of multiple ignition and fuel signals, guaranteeing synchronized turbine startup, operation, and shutdown. LED indicators provide real-time feedback on signal status and diagnostic conditions, enabling operators to monitor performance. The card also integrates protection mechanisms, including current-limiting resistors, clamping diodes, and transient suppression, to prevent damage from voltage spikes or shorts. Connection to the main firing board is established via a 28-pin connector, allowing reliable bi-directional communication of firing commands and interlocks, ensuring safe and precise turbine operation under all conditions.

FUNCTIONS OF SYSTEM FIRING DAUGHTER CARD:

It provides TTL-level signal conditioning, digital sequencing logic for turbine ignition and fuel commands, and diagnostic status outputs. The card ensures precise coordination of firing signals during startup, operation, and shutdown while protecting both itself and the main firing board from electrical faults. It connects via a 28-pin edge connector, enabling reliable bi-directional communication and integration of interlocks and auxiliary signals.

• Signal Conditioning: Buffers and shapes TTL-level signals received from the main firing control board to maintain proper voltage levels and signal integrity for downstream ignition and fuel circuits.
• Digital Sequencing: Implements logic for coordinated turbine ignition and fuel sequencing, ensuring precise timing of multiple firing signals during startup, operation, and shutdown.
• Status Monitoring: Provides onboard LED indicators to display operational status and diagnostic information for real-time monitoring of signal integrity.
• Interfacing: Connects to the main firing board via a 28-pin connector, enabling bi-directional communication for firing commands and interlock signals.
• Protection: Incorporates current-limiting resistors, clamping diodes, and transient suppression circuits to protect both the daughter card and the main firing board from voltage spikes, shorts, or electrical faults.
• Integration: Acts as an auxiliary module that expands the capability of the main firing board by managing additional ignition circuits and interlocks required for safe turbine operation.

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FREQUENTLY ASKED QUESTIONS:

What is the primary function of the System Firing Daughter Card in turbine control systems?

The card is responsible for generating precise gate firing pulses to power devices such as thyristors or SCRs in the excitation and power conversion stages. It ensures phase synchronization, accurate timing, and protection coordination within the firing sequence.

How does the card synchronize with the turbine control system?

It uses phase-locked loop (PLL) circuitry and reference clock inputs from the main control board to align its firing pulses with the system frequency. This synchronization ensures stable turbine operation and prevents misfiring under load conditions.

What diagnostic signals can be measured for verifying firing accuracy?

Oscilloscope measurements at the firing pulse output test points should show pulse widths in the microsecond range, with consistent amplitude (typically 12�18 V) and precise phase relation to the reference waveform.