Amplifier board debugging notes

This page contains a list of all currently known problems with the amplifier board and the solutions implemented

Improper DC levels from voltage regulators

Description

Incorrect voltage levels on the basis of the transistors representing the input stages for base amplifier and summing circuits.

Cause

Pinout of voltage regulators (ZR431L) used on ampplifier board.

The pads for pins Gnd and Vz of the voltage regulators were reversed. The proper assignment of pins is shown in the adjacent figure.

Solution

• the ICs were rotated such that 2 pins (Vref and Gnd) are bonded to their nets. The loose Vz pin was connected via wire to its proper proper net.
• modifications of the PCB layout is pending

Wrong voltage on R_C/R_D junction

Description

A voltage of 2.75 V was measured on the junction between R_C and R_D resistors, instead of 2.25 

Cause

Resistors R_C and R_D (2.5 kΩ and 2.0 kΩ respectively) have been reversed. The is an error on the layout: the placement designation and the silk-screen labeling is wrong.

Solution

• The resistors have been swapped.
• modifications of the PCB layout is pending

FET switch compatibility

Description

The FET switch BF1108 was not available in our market. Only its mirror package variant BF1108R could be procured.

Solution

• Temporary solution: The adaptation of the board for the BF1108R is shown in the adjacent figure. The IC is positioned in the shown orientation and its pins (pads) linked as shown.
• modifications of the PCB layout is pending