SB220 SB221 Rectifier Board

The CTR Engineering SB220rect SB220 rectifier/metering board is a simple but greatly advanced rectifier, bias, and metering board. It faithfully retains OEM Heathkit labeling, wiring, and metering.

SB220 rectifier power supply board

This board produces precise meter readings while using standard off-the-shelf part values for components while being easy to install and service. This board fully protects the meters and other parts from damaging high-voltage shorts such as tube arcs. With on board protection,there is no need to clamp at the meters with unsightly diodes tacked in.

Additionally this board, with simple resistor changes, permits use of meter movements of 1 mA and 300 mV or any value lower than those two limits. In other words a 1mA 50 mV movement or 50 uA 200mV meter would be workable with minor resistor changes.

This board has the following features:

  1. Internal bias using two 5-watt 3.9Vdc Zener diodes
  2. Board trace spacing conforms to standards of 100 mils per kV. This ensures long reliable board life. E.g. 3kV requires 0.3” board spacing
  3. Use of standard fixed resistors with precise metering results
  4. Full meter protection with clamp diodes. There is no need to clamp at meters
  5. Easily adapted for accurate use with replacement meters up to 1mA and 350mV
  6. Rectifier headroom over 1.6 times at the SSB HV setting
  7. Retains OEM Heathkit wiring size, letters, and positions
  8. 10-ohm on-board 9kV rated flameproof fault resistor designed for exact application
  9. Ground trace redundancy with wide double-layer grounds
  10. RF bypassing on filament center tap and B- rail
  11. Full solder mask high-quality printed circuit board
  12. Clean properly-engineered layout

The instructions are here 

This assembled board is $60 plus shipping.
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