Denon AVR-789 Service Manual download pdf (Page 2)

AVR-1909/789, AVC-1909

Please heed the points listed below during servicing and inspection.

◎ Heed the cautions!

Spots requiring particular attention when servicing, such

as the cabinet, parts, chassis, etc., have cautions indicated

on labels or seals. Be sure to heed these cautions and the

cautions indicated in the handling instructions.

◎ Caution concerning electric shock!

(1) An AC voltage is impressed on this set, so touching in-

ternal metal parts when the set is energized could

cause electric shock. Take care to avoid electric shock,

by for example using an isolating transformer and

gloves when servicing while the set is energized, un-

plugging the power cord when replacing parts, etc.

(2)There are high voltage parts inside. Handle with extra

care when the set is energized.

◎ Caution concerning disassembly and

assembly!

Though great care is taken when manufacturing parts from

sheet metal, there may in some rare cases be burrs on the

edges of parts which could cause injury if fingers are

moved across them. Use gloves to protect your hands.

◎ Only use designated parts!

The set's parts have specific safety properties (fire resis-

tance, voltage resistance, etc.). For replacement parts, be

sure to use parts which have the same properties. In par-

ticular, for the important safety parts that are marked z on

wiring diagrams and parts lists, be sure to use the desig-

nated parts.

◎ Be sure to mount parts and arrange

the wires as they were originally!

For safety reasons, some parts use tape, tubes or other in-

sulating materials, and some parts are mounted away from

the surface of printed circuit boards. Care is also taken with

the positions of the wires inside and clamps are used to

keep wires away from heating and high voltage parts, so

be sure to set everything back as it was originally.

◎ Inspect for safety after servicing!

Check that all screws, parts and wires removed or discon-

nected for servicing have been put back in their original po-

sitions, inspect that no parts around the area that has been

serviced have been negatively affected, conduct an insu-

lation check on the external metal connectors and between

the blades of the power plug, and otherwise check that

safety is ensured.

(Insulation check procedure)

Unplug the power cord from the power outlet, disconnect

the antenna, plugs, etc., and turn the power switch on. Us-

ing a 500V insulation resistance tester, check that the in-

sulation resistance between the terminals of the power

plug and the externally exposed metal parts (antenna ter-

minal, headphones terminal, microphone terminal, input

terminal, etc.) is 1MΩ or greater. If it is less, the set must

be inspected and repaired.

Concerning important safety

parts

Many of the electric and structural parts used in the set

have special safety properties. In most cases these prop-

erties are difficult to distinguish by sight, and using re-

placement parts with higher ratings (rated power and

withstand voltage) does not necessarily guarantee that

safety performance will be preserved. Parts with safety

properties are indicated as shown below on the wiring dia-

grams and parts lists is this service manual. Be sure to re-

place them with parts with the designated part number.

(1) Schematic diagrams ... Indicated by the z mark.

(2) Parts lists ... Indicated by the z mark.

Using parts other than the designated

parts could result in electric shock, fires or

other dangerous situations.

SAFETY PRECAUTIONS

The following check should be performed for the continued protection of the customer and service technician.

LEAKAGE CURRENT CHECK

Before returning the unit to the customer, make sure you make either (1) a leakage current check or (2) a line to chassis

resistance check. If the leakage current exceeds 0.5 milliamps, or if the resistance from chassis to either side of the

power cord is less than 460 kohms, the unit is defective.

CAUTION

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Denon AVR-789 Service Manual Page 2

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