repair practice nad 3020i stereo integrated amplifier do easier

First
The NAD 3020 series amplifiers are the stuff of legends. Here is quite simply one of the best sounding, best designed and best built budget priced range of integrated amplifiers ever made.

History
NAD 3020i is the improved version of well-known 3020, from the list of ‘Ten Most Significant Amplifiers of All Time

Stereo Amplifier 3020i NAD


Specifications:

• Power output: 20 watts per channel into 8Ω (stereo)
• Frequency response: 6Hz to 80kHz
• Total harmonic distortion: 0.03%
• Damping factor: 40
• Input sensitivity: 2.4mV (MM), 150mV (line)
• Signal to noise ratio: 75dB (MM), 100dB (line)
• Dimensions: 80 x 420 x 250mm
• Weight: 5kg
* Country : Canada ontario
* Manufacturer / Brand : NAD
* Year1991

Technical
Number of Transistors
Current supply (AC) / 100 or 120 or 220 or 240 Volt
loudspeaker- This model requires external speaker(s).Power out40 W (60 W max.)
Material : metal casefrom

Soft problem
Transistor output : 2N3055  MJ2955
R453 (180om was open),
Q411: 2SD669A
Q413: 2SB649A
Main voltage output transistor : 28 CT -28
Can be over switch transformer for output 4 and 8 Ohms

tone control
Bass and treble only

Masterpiece until next will be there are.

the schematics is almost the same with NAD 4335PE

3 inputs selection
1 tape input monitor

Important
Speaker impedance switch should be in 8 ohm position while adjust center voltage and idling current.

 Adjustment No load connected
A. Center voltage
1. Connector DC millivoltmeter to L channel output terminal.
2. Turn on and adjust to 0 V +/-30mV with R411 (470 ohm). Connect DC millivoltmeter to R channel output terminal and adjust R412 to 0 V+/-30mV.

B. Idle current
1. Remove solder short across R455 and R456.
2. Connect DC millivoltmeter across R455 (1 ohm) (output transistor's collector resistor) and adjust R443 for 26-30mV reading on meter. Repeat adjustment with R444, connecting meter across R456 (1 ohm).

3. Leave power on for minimum 5 minutes.

Final Adjustment
C. Center voltage
1. Repeat step A about.
D. Idle current
1. Repeat step B and adjust with R443, R444 for 30mV reading on meter. 2. After the alignment is finished, 1 ohm resistor R455, R456 shorted by solder short

transistor 30 peaces
diode : 18 peaces