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Ver. 1 
SERVICE MANUAL
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JP |
E3 |
E2 |
EK |
E2A |
E1C |
E1K |
EUT |
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DN-A300M |
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INTEGRATED STEREO AMPLIFIER
●For purposes of improvement, specifications and design are subject to change without notice.
●Please use this service manual with referring to the operating instructions without fail.
●Some illustrations using in this service manual are slightly different from the actual set.
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●8
PROFESSIONAL BUSINESS COMPANY
X0394 V.01 DE/CDM 0807
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 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 internal 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, unplugging 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 resistance, voltage resistance, etc.). For replacement parts, be sure to use parts which have the same properties. In particular, for the important safety parts that are marked z on wiring diagrams and parts lists, be sure to use the designated parts.
Be sure to mount parts and arrange the wires as they were originally!
For safety reasons, some parts use tape, tubes or other insulating 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 disconnected for servicing have been put back in their original positions, inspect that no parts around the area that has been serviced have been negatively affected, conduct an insulation 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. Using a 500V insulation resistance tester, check that the insulation resistance between the terminals of the power plug and the externally exposed metal parts (antenna terminal, headphones terminal, microphone terminal, input terminal, etc.) is 1MΩ or greater. If it is less, the set must be inspected and repaired.
CAUTION Concerning important safety parts
Many of the electric and structural parts used in the set have special safety properties. In most cases these properties are difficult to distinguish by sight, and using replacement 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 diagrams and parts lists is this service manual. Be sure to replace 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.
2 DN-A300M
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500V |
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MΩ |
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(2) には十分ご注意ください。
図、部品表にz
が維持されるとは、限りません。安全上の特性を持った部 品は、このサービスマニュアルの配線図、部品表につぎの ように表示していますので必ず指定されている部品番号 のものを使用願います。
(1) … z
(2) … z
3 DN-A300M
DIMENSION
4 DN-A300M
WIRE ARRANGEMENT |
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If wire bundles are untied or moved to perform adjustment or |
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parts replacement etc., be sure to rearrange them neatly as |
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they were originally bundled or placed afterward. |
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Otherwise, incorrect arrangement can be a cause of noise |
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generation. |
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Wire arrangement viewed from the top |
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Back Panel side
Front Panel side
5 DN-A300M
CAUTION OF WIRE ARRANGEMENT
Observe that the wires do not contact heat producing parts (heatsink, resistors, fuse, etc.).
Fix the wiring of the wire like this photo
B
C
A
( )
E D
Clamp
Detail A |
Detail D |
Detail B
Detail C |
Detail E |
The wire is pulled in the direction of arrow.
6 DN-A300M
ADJUSTMENT
DC Offset Current / Idling Current
Required measurement equipment: DC Voltmeter
1.Setup
(1)Place the unit at an ordinary position avoiding direct air flow from an air-conditioner or fan. Do the adjustment at a temperature between 15 °C (59 °F) and 30 °C (86 °F).
(2)Set control as follows.
• POWER switch |
→ OFF ( j ). |
• VOLUME control |
→ fully counterclockwise |
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( c min.) |
• SPEAKER terminals |
→ open: do not connect the |
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speakers, dummy load |
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etc. |
2.Adjustment
●DC Offset Current
(1)Connect SPEAKER terminals to the DC Voltmeter.
(2)Connect power cord to AC wall outlet, and turn POWER switch "ON" ( h ).
(3)Right after power on, adjust test points VR400 and VR401 of Power Amp P.W.B. so that the DC voltmeter reads 10 ±1mV.
(4)Then after 2 minutes warm up adjust VR400 and VR401 so that the DC voltmeter reads 10 ±1mV.
(5)And after 10 minutes warm up adjust VR400 and VR401 so that the DC voltmeter reads 10 ±0.5mV.
●DC Offset Current
(1)Remove top cover. And then connect DC Voltmeter to the test points TP300 and TP301 of Power Amp P.W.B.
(2)Connect power cord to AC wall outlet, and turn POWER switch "ON" ( h ).
(3)Right after power on, adjust test points VR403 and VR404 of Power Amp P.W.B. so that the DC voltmeter reads 10 ±1mV.
(4)Then after 2 minutes warm up adjust VR403 and VR404 so that the DC voltmeter reads 10 ±1mV.
(5)And after 10 minutes warm up adjust VR403 and VR404 so that the DC voltmeter reads 10 ±0.5mV.
DC /
: DC Voltmeter
囲温度は、15 30
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→ OFF ( j) |
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→ ( c) |
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→ ( |
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●DC
(1)DC Voltmeter
(2)AC100V 95 105V"ON" ( h)
(3)10 ± 1mV VR400 VR401
(4)2 10 ± 1mVVR400 VR401
(5)10 10 ± 0.5mVVR400 VR401
(1) ポイント(T.P.300, T.P.301) DC Voltmeter
(2)AC100V 95 105V"ON" ( h)
(3)10 ± 1mV VR403 VR404
(4)2 10 ± 1mVVR403 VR404
(5)10 10 ± 0.5mVVR403 VR404
7 DN-A300M
DC Voltmeter |
DC Voltmete |
PowerPower
Trans Trans
VR404 VR404 |
VR403 VR403 |
T.P. 301T.P. 301 |
T.P. 300T.P. 300 |
VR401 VR401 |
VR402 VR402 |
Volume Volume
8 DN-A300M
BLOCK DIAGRAM
VOLTAGE:+15V/-15V
VOLTAGE:9.1V
VOLTAGE:+5V
VOLTAGE:+5V
9 DN-A300M
---MEMO---
10 DN-A300M
SEMICONDUCTORS
Only major semiconductors are shown, general semiconductors etc. are omitted to list.
The semiconductor which described a detailed drawing in a schematic diagram are omitted to list.
UPD78F0502MC(T) (IC109)
Functional Block Diagram
11 DN-A300M
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