SECTION - 5
SERVICE INSTRUCTION
5.1
5.2
GENERAL :
The instrument has been tested throughly and then released for dispatch. Nor-
mally, 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.
TROUBLE SHOOTING TECHNIQUES :
5.2.1 INTRODUCTION : The trouble shooting procedure is arranged in an order that
checks the simple trouble possibilities before proceeding to extensive troubleshooting.
5.2.2 CONTROL 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.
5.2.3 SYSTEM AND ASSOCIATED EQUIPMENT :
Before trobleshooting the 1791 (350)
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.
5.2.5 INTERNAL 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.
5.2.6 CIRCUIT 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.
5.2.7 COMPONENT 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.
5.2.8 TRANSISTORS 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
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