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PROCEDURE TO OPEN AMPLIFIER

1.STEP –1 Removing top cover and trim. : Unscrew 4 top screw marked (A) to remove top cover and trim.

STEP-2 To get access to rear of PCBs : Remove the shield by unscrewing 2x screws marked (B) and 2 nos. screws and nuts holding the shield with base (Not shown.)

STEP-3 To get access to front of PCBs : Remove all knobs of volume controls. Remove 6 screws marked (C) meant for holding dial plate to remove the dial plate.

Now both front panel mounted PCBs and components are now access able both front and back and can be serviced without dismantling PCBs.

IMPORTANT SERVICE HINTS : A Method of Replacing Transistors : While replacing transistors please ensure the various mounting accessories as indicated in Fig.2 for various transistors indicated are properly fitted. Any loose fitting of power transistors bush like 3773 and 3055H may result into over heating of power transistor .Hardwires like MICA washer, Insulating bush etc. should also replaced. Application of heat sink compound properly also plays important part. For correct application following procedure should be followed.

1.Clean mating surfaces. / 2. Apply a small quantity of heat sink compound, to both (Evenly Spread ) surfaced to be mated. / 3.Be sure there is on foreign objects in the compound such as brush hair. / 4. Press surface together and squeeze out excess material. / 5. Wipe excess compound to help prevent dirt accumulation.

B) Adjustment of no signal current after changing power transistors.

(1). Make all control minimum including Master and tone control / (2) De-solder one wire of 12 A Thermal protector and connect between the wire and terminal of circuit protector an amp. Meter having the range of at least 200mA. Switch on the amplifier and note the amp. meter reading.( 3 ) The current should be between 80mA and 110mA In case it is beyond above range then adjust this with pre-set transistors.