View source for 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 ==
[[Image:AmpBoard_Vref.png|frame|Pinout of voltage regulators ([http://www.powerdi.com/datasheets/ZR431L.pdf ZR431L]) used on ampplifier board.]]

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

=== Cause ===

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<sub>C</sub>/R<sub>D</sub> junction ==
[[Image:AmpBoard_FETorient.png|frame|Quick fix for the package-footprint mismatch of the FET swtich]]

=== Description ===
A voltage of 2.75&nbsp;V was measured on the junction between R<sub>C</sub> and R<sub>D</sub> resistors, instead of 2.25&nbsp;

=== Cause ===
Resistors R<sub>C</sub> and R<sub>D</sub> (2.5&nbsp;k&Omega; and 2.0&nbsp;k&Omega; 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'''