Wang 600 Fault Summary Next Log Entry

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S/N CC 2001 - List of Faults Found & Fixed

1 Main Power Supply

• Mains wiring upgraded for safety Done
• Shorted rectified diode replaced Done
• Main filter capacitors replaced Done
• Filter capacitor original design error corrected Done

2 -12v Regulator

• Driver transistor replaced Done
• 723 regulator IC replaced Done

3 Volt Clamps on High-Risk Rails

• Clamp fitted to +5v to protect 200+ TTL ICs Done
• Clamp fitted to -11.5v to protect vintage Mostek MK4008 RAM ICs Done

4 +12v Regulator

• Ampacity improved by installation of 7812 regulator Done

5 Wire ROM Power

• Shorted tantalum in wire driver supply replaced Done

6 Corroded IC Sockets

• Two ICs on the 5964 ALU board had extensive corrosion in and under their sockets
  • Sockets removed, board and ICs cleaned, ICs directly soldered Done

7 Wire ROM Data

• One silent column, KK field bit 1, sense circuit fault Repaired, faulty sense latch IC replaced
• Four silent rows, possible select diode or broken wire Not Repairable, Worked-around with ROM Emulator

8 ROM Emulator

• Wire ROM will be replaced with ROM emulator Done
• Original ROM image downloaded, repaired and uploaded to emulator Done

9 Faulty 9946 IC in MAVx gating

• 9946 quad-NAND with stuck outputs prevents RAM addressing
• Successfully replaced with 74H01 IC Done

10 Faulty 9946 IC on 6187 Keyboard PCB

• 9946 quad-NAND prevented keyboard RECORD PROG and STEP keys from working
• Successfully replaced with 74H01 IC Done

11 Faulty ICs x3 and Dry Joints on 6184 PCB

• 2x faulty 9946 quad-NANDS stopped keyboard enable
• Dry joints caused intermittent operation of the keyboard enable circuit
• Faulty 7404 hex inverter prevented keycode data from latching into the logic engine