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

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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

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Contents BK Precision Limited Two Year Warranty Table of Contents Limit Setting Output ON/OFF SwitchSection General Information Description Remote Programming With External 5K PotSection Specifications Section Installation Repackaging for Shipment Input TAP Selection for 230V OperationSection Operating Instructions Readjust the current limit in the remote sensing mode Reverse Voltage Loading Output Capacitance Reverse Current Loading USE the Proper Power Cord Operators Safety SummaryTerms in this Manual Terms AS Marked on Equipment For Qualified Service Personnel only Servicing Safety SummaryDo not Service Alone USE Care When Servicing with Power onTrouble Shooting Techniques Section Service Instruction GeneralServicing shall be done only by Qualified personnel Repairs & Maintenance Page Parts Ordering & Replacing REF. PCB no PIN noPage Page Fuse Blows Fault Finding ProcedureFuse Blows Unregulated O/P Voltage Unregulated O/P VoltageNo O/P Voltage No Output VoltageNo DPM Indication No DPM IndicationDPM not Read Unit not Take Current Unit not Take CurrentUnit Directly Goes To CC Unit Directly Goes to CCPoor Line Regulation No Current ControlNo Current Control Poor Line RegulationCV, CC, LED not Glow Poor Load RegulationPoor Load Regulation Remote Sense not OK External Programming not OKExternal Programming Not OK L1791-FP-CNT-0603 PCB Assy Section Part List & Schematics1KPF/100V, Disc 2P2W SW Push ButtonPS-PREG-1791-0503 PCB Assly SW1 Grey Colour CAP for Push Switch SW2 SW3DPM/01 REV 01 X PS-PWR-L1791-0703A PCB Assly PS-AUX-DC-L1791-0503 PCB AsslyMain Chassis Assly Front Panel AsslyBack Trough Assly Front Panel Layout Back Panel Layout TOP View Bottom View of Model 1790 Front Panel Control PCB of 1790 Power Module PCB of 1790 PRE Regulator / AUX. P/S PCBs 1790 Precision Corp Service InformationPrecision Corp
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