EHHA Rev A Assembly


Board Assembly Instructions

The first step in assembly is to decide which board sections to keep and to break off the ones you don't want.

The second step is to decide what diodes to use in the heater supply.

  • If you are using a 6.3V-7V transformer then select 1N5822 Schottky rectifiers.
  • If you are using a 9V transformer then select UF4002 rectifiers.

Have the components specific to your build in the parts box.

Solder the components to the board from lowest profile to highest, roughly in this sequence:

  1. Flat placement resistors, diodes (tombstoned later), and LEDs.
  2. Small signal transistors.
  3. Film capacitors.
  4. Trimpots, sockets, and connectors.
  5. Mount vertical diodes with cathodes up and anodes down, like this:

    EHHA Rev A Vertical Diode

  6. Small electrolytic capacitors and tube sockets.
  7. Install the opamp.
  8. Mount the transistors loosely to the heatsinks. Press the heatsinks to the board inserting the pins of the transistors.
  9. Hold the heatsinks down (or solder them) then solder the transistor pins.
  10. Large electrolytics on the PS and heater boards.
  11. DO NOT connect the PS or heater supply to the amps yet.

Clean up the solder flux residue from the board with isopropyl alcohol (or electronics flux remover) and a brush.

Inspect all solder connections carefully, using a magnifying glass, to make sure there are no solder bridges or cold solder joints. Use a multimeter in ohms scale to check for short circuits. Correct any mistakes before proceeding.