PWB68A993125 GE Speedtronic Mark II SCR Gate & Filter Printed Wiring Board
PWB68A993125 GE Speedtronic Mark II SCR Gate & Filter Printed Wiring Board - Image 2
PWB68A993125 GE Speedtronic Mark II SCR Gate & Filter Printed Wiring Board - Image 3
PWB68A993125 GE Speedtronic Mark II SCR Gate & Filter Printed Wiring Board - Image 4
PWB68A993125 GE Speedtronic Mark II SCR Gate & Filter Printed Wiring Board - Image 5

PWB68A993125 GE Speedtronic Mark II SCR Gate & Filter Printed Wiring Board

  1. PWB68A993125 – Mark II SCR Gate & Filter Card (Target Model)
  2. PWB68A993124 – Mark II SCR gate card sibling variant
  3. TP202QSS RMS-9 – GE TMR turbine I/O module
  4. IS230JPDGH1B – Mark VIe JPDG power distribution module
  5. V7768-320001 A2 – 6U VME SBC
  6. VMIVME-4150 – VME analog output module
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Description

PWB68A993125 GE Speedtronic Mark II SCR Gate & Filter Printed Wiring Board

 

Product Application

PWB68A993125 belongs to GE legacy Speedtronic Mark II analog turbine control system (not Mark VIe). It is a chassis-mounted discrete analog circuit board, used in older heavy-duty gas turbine control cabinets. Core functions: generate gate trigger pulses for SCR thyristors, filter high-frequency noise on fuel control analog signals, condition error signals for fuel valve closed-loop regulation. It receives low-level control signals from Mark II main control logic board and outputs amplified trigger pulses to SCR power rectifier stack for fuel control. Widely used in legacy power plant gas turbines for fuel regulation and turbine temperature limiting control.

PWB68A993125

Product Specifications

  • Part Number: PWB68A993125
  • Manufacturer: General Electric (GE)
  • Product Type: SCR Gate Drive & Signal Filter PWB (Printed Wiring Board)
  • System Compatibility: Speedtronic Mark II Gas Turbine Control
  • Power Supply: 115–125VDC control power
  • Function: SCR thyristor gate pulse generation, analog signal filtering & conditioning
  • Termination: Multi-point screw terminal block on front edge
  • Mounting: Chassis standoff mounting inside Mark II control rack
  • Operating Temperature: -20 ℃ ~ +70 ℃
  • Humidity: 5% ~95% RH non-condensing
  • PCB: Conformal coated
  • Product Status: EOL, only refurbished / surplus spare stock for legacy Mark II turbine maintenance
  • Approx. Weight: 0.65 kg

 

Core Technical Parameters

  • Analog discrete hardware circuit, no microprocessor / firmware
  • Built-in RC filtering network to suppress EMI noise from field sensors
  • Isolated gate pulse drive for SCR thyristors
  • Signal level amplification for fuel control error signal
  • Conformal coating protects PCB from corrosive gas in power plant cabinet
  • Screw terminal design for easy field wiring connection
  • Compatible sibling part: PWB68A993124 (similar Mark II SCR card, limited cross substitution)

 

Recommended Matching Spare Parts & Accessories (8 Items)

  1. GE Speedtronic Mark II turbine control rack
  2. Mark II logic & comparator boards
  3. SCR thyristor power stack
  4. 125VDC redundant control power supply
  5. Shielded twisted pair analog signal cable
  6. Replacement capacitors & resistors for board repair
  7. Terminal lugs and screw terminals
  8. Mark II turbine maintenance manual and schematic drawings

PWB68A993125

Product Features

✅ SCR Gate Pulse Generation Generates stable trigger pulses to fire thyristors in fuel control SCR rectifier stack for turbine fuel regulation.

✅ Analog Signal Noise Filtering Onboard passive filter circuit removes high frequency interference from temperature and speed feedback signals.

✅ Conformal Coated PCB Protects electronic components from dust, moisture and corrosive atmosphere in power plant control room.

✅ Chassis Mount Screw Terminal Interface Front screw terminals simplify signal wiring and field troubleshooting without removing the whole rack.

✅ Pure Analog Hardware Circuit No CPU or software; function implemented by resistors, capacitors, diodes and transistors, typical for Mark II analog control.

✅ Critical Fuel Loop Signal Conditioning Amplifies and conditions fuel demand error signal to stabilize gas turbine fuel valve control.

✅ Legacy Turbine Spare Part For maintaining old Mark II units; no new production, only surplus/refurbished spares available.

 

Installation Guidelines

  1. Power off Mark II turbine rack and lock out control power (125VDC).
  2. Mount PWB68A993125 onto rack standoffs and secure fasteners.
  3. Connect field analog feedback signals and SCR gate wiring to front screw terminals.
  4. Verify all wiring matches Mark II schematic diagram.
  5. Restore 125VDC control power to rack.
  6. Perform signal measurement with multimeter/oscilloscope, check filtered analog signal and SCR trigger pulses.
  7. Complete static fuel loop test before turbine rolling.
  8. Monitor fuel control response and SCR firing during unit commissioning.

 

Maintenance Instructions

Daily Maintenance Monitor fuel control loop stability and SCR firing health via turbine control panel indication.

Periodic Maintenance (Every 6–12 months) Clean board dust, inspect capacitors for leakage, check terminal screw tightness. Keep original schematic for reference.

Fault Maintenance

  • Poor SCR firing / unstable fuel control: Inspect capacitors, resistors and solder joints on the PWB.
  • Signal noise / fluctuation: Check shield cable grounding and filter component aging.
  • No gate pulse: Verify 125VDC control power and input error signal.
  • This is analog hardware board, component aging (caps) is most common failure mode.

Long-Term Operation Tips Keep rack temperature controlled within -20~+70℃. Store spare PWB68A993125 in dry environment. Keep Mark II schematic drawings for repair.

 

Brand Same‑Series Models (6 Models)

  1. PWB68A993125 – Mark II SCR Gate & Filter Card (Target Model)
  2. PWB68A993124 – Mark II SCR gate card sibling variant
  3. TP202QSS RMS-9 – GE TMR turbine I/O module
  4. IS230JPDGH1B – Mark VIe JPDG power distribution module
  5. V7768-320001 A2 – 6U VME SBC
  6. VMIVME-4150 – VME analog output module

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