DVO7
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← Repair Guides|Power Supply Recap
medium120 min

Power Supply Recap

Symptoms this guide addresses

  • •Dead / no boot
  • •Hum or noise on outputs
  • •Intermittent operation
  • •Blown fuse

Tools required

  • •Soldering iron
  • •Desoldering tool
  • •Multimeter
  • •Replacement electrolytics

Overview

The Emulator I has no backup battery — like the EII, it loads everything from disk at boot, so PSU work here is purely about the supply itself. After 40+ years the electrolytic capacitors are the prime suspects.

Procedure

  1. Fully discharge and recap the supply: replace all electrolytics with same-or-higher voltage, same capacitance (105 °C parts recommended).
  2. Inspect the rectifier diodes and bridge for shorts; replace the mains fuse only after confirming no downstream short.
  3. Verify each rail is in spec before reconnecting the voice boards — an over-voltage on the +15 V rail can take out the SSM2044 filter chips (see SSM2044 Filter Service).
  4. Check the steel chassis ground bonding — the EI's all-metal construction relies on it for safety and hum rejection.
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