Service manual

20
POWER SUPPLY
The Midas XL3 has an external 19" rack mounting power supply to provide the three voltage
rails to power the console, +18V and -18V DC at 12 amps per rail and +48V phantom power
at 500mA for capacitor microphones and direct injection boxes. It is fitted with two fully pro-
tected outputs through polarised 19 pin multipin connectors, one female for connection to the
console and one male for connection to an additional power supply if used for fail-safe operation.
The two connectors are parallel wired and the three power modules incorporate blocking diodes,
so that the power supplies can share the load but never feed power into each other in the event
of one unit failing. Each 18 volt block incorporates an over-temperature sensor which switches
off the affected unit. If this occurs while two power supplies are connected, there will be no effect
on the operation of the console since load sharing and switchover is automatic; however, the
relevant monitoring LED on the front panel will be extinguished. The relevant block will reset
automatically on cooling and the LED will come back on when this happens.
Connection of the power supply to the console is via a 5 meter multiconductor cable fitted with
polarised 19 pin connectors, one male and one female.
PLEASE NOTE THAT THE POWER SUPPLY CONTAINS CIRCUITRY WHICH GEN-
ERATES LETHAL VOLTAGES. NOT ONLY IS IT POWERED BY HIGH VOLTAGE,
BUT THE SWITCH MODE BLOCKS FOR THE 18v RAILS CREATE VOLTAGES FAR
IN EXCESS OF THE MAINS INPUT. ALL SERVICING OF THESE UNITS MUST BE
REFERRED ONLY TO AUTHORISED SERVICE AGENTS OF KLARK TEKNIK. ON
NO ACCOUNT MUST SERVICE WORK BE ATTEMPTED BY ANYONE ELSE. IF IT
IS, THE WARRANTY WHICH COVERS THE EQUIPMENT BECOMES INVALID,
AND KLARK TEKNIK ACCEPT NO LIABILITY FOR CONSEQUENT DAMAGE TO
THE CONSOLE OR ANCILLARY EQUIPMENT. QUALIFIED SERVICE PERSONNEL
ONLY MAY UNDERTAKE THE SERVICE WORK DETAILED BELOW.
Voltage Change-over.
There are five steps involved in this operation. It is most
important that all five are carried out together, and that power
is not applied to the unit when change-over procedures are
incomplete, and that the power is disconnected by unplugging the
mains lead before work is commenced.
1. Change the fuse.
The fuse holder is located on the back of the unit below the
mains input plug. The correct fuse ratings are as follows:-
220/240 volt operation: 5A.
100/110 volt operation: 10A.
The fuse is 20mm, HRC type.