B&K 1794 Section Service Instruction General, Servicing shall be done only by Qualified personnel

SECTION - 5

SERVICE INSTRUCTION

5.1GENERAL :

The instrument has been tested throughly and then released for dispatch.Normally, the unit works satisfactorily under all condition. However due to ageing / misuse or malfunctioning, the unit may become defective. In case, the user wants to carryout Servicing, the following instructions will be helpful in rectifying the defects.

The Servicing shall be done only by Qualified personnel.

5.2TROUBLE SHOOTING TECHNIQUES :

5.2.1INTRODUCTION: The trouble shooting procedure is arranged in an order that checks the simple trouble possibilities before proceeding to extensive troubleshooting.

5.2.2CONTROL SETTINGS : Incorrect control settings can seem like a trouble that does not actually exist. If there is any question about the correct function or operation of any control, see the Operating Instructions section.

5.2.3SYSTEM AND ASSOCIATED EQUIPMENT: Before trobleshooting the 1790 (349), check for proper input fuse as per part list is intac. Check the line voltage at the power source before connecting the mains cord is rated for the correct input voltage. Verify that the front panel controls are kept at minimum position. The output terminals must be free from any load connecting leads.

5.2.4 VISUAL CHECK :	Many	troubles	can be located by visual clues such
as unsoldered connections,		broken	wires, damaged circuit board, damaged
components, etc.

5.2.5INTERNAL ADJUSTMENT :Check the Adjustment of the suspected circuit if the trouble is obviously in a certain circuit. The trouble may only be a result of misadjustment and may be corrected by readjustment.

5.2.6CIRCUIT ISOLATION: Note the trouble symptoms. These often identify the circuit in which the trouble is located. When trouble symptoms appear in more than one circuit,check the effected circuits by making waveform and voltage measurements.

5.2.7COMPONENT CHECKING : If a component cannot be disconnected from its circuits, then the effects of the associated circuitry must be considered when evaluating the measurement. Except for soldered-in transistors and integrated circuits, most components can be lifted at one end from the circuit board.

5.2.8TRANSISTORS AND IC's : Turn the power switch off before removing or replacing any semiconductor. A good check of transistor operation is actual performance under operating conditions. A transistor can most effectively be

10