User Guide

Circuit Description

The Midas XL88 Matrix Mixer has been designed not only to provide the highest

possible quality sound processing facilities, but also the greatest possible degree of

reliability. However, no unit of such complexity can be expected never to need

service, and to help anyone undertaking such work circuit descriptions will be

found below. The less experienced technician or operator may find the following

notes useful in an emergency fault finding when more experienced help may not

be available.

The priority in fault finding is to adopt a logical approach, as this is the quickest

way to identify the precise source of a problem. For instance, if an input module

appears to have failed, it will be helpful to establish with greater accuracy where

the failure is. Does the direct output function even though the matrix output does

not? [Failure in matrix buffer or output.]. Is the signal present at matrix output

PFL? [Fault in mute circuit or output amplifier]. In this way a particular circuit

block can be identified as faulty, and a careful inspection will often reveal a

disconnected wire, a damaged component, or a suspect IC that can be changed.

Furthermore, if help is sought over the telephone, it will be helpful to have the

greatest possible amount of detail for the technician to work with.

When performing tests on the console, it is tempting to unplug modules without

switching off the power supply THIS MUST NEVER BE DONE, AS IT NOT

ONLY DESTROYS SOME COMPONENTS AT ONCE, BUT LEADS TO THE

EARLY FAILURE OF MANY THAT APPEAR TO HAVE SURVIVED. The

power supply is designed to bring the console to full power gradually, which

protects sensitive components from damage caused by voltage spikes created by

sudden powering up.