BK Precision 1794, Instruction Manual

SECTION - 5

SERVICE INSTRUCTION

5.1

GENERAL :

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.

5.2

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 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.

5.2.5 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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