LTO MC250.8 User manual

MODEL: MC250.8

CONTENT
1. INTRODUCTION……………………………………………………………………………..1
2. TECHNICAL SPECIFICATION……………………………………………………………..
3. BLOCK DIAGRAM……………………………………………………………....................3
4. SCHEMATIC DIAGRAM…………………………………………………………………….4
5. WIRING DIAGRAM…………………………………………………………………………12
6. PCB LAYOUT……………………………………………………………………………….
7. TEST PROCEDURE…………………………………………………………....................18
8. EXPLODED VIEW & MECHANICAL PARTS LIST…………………………………….
9. BOM………………………………………………………………………………………….25
2
1
3
22

Innovative design and high stability power amplifier
Fan-cooled AB class high power amplifier in 19", 2U size
8 independent channels with separate protection system
DC, infrasonic, overheat & short circuit protection
Smart-designed protection system for auto re-operation after fault
Parallel-input: channel 1 to channel 2, channel 3 to channel 4, channel 5 to channel 6, channel 7 to channel 8
Allowing selection of Stereo, Bridge or parallel operation
Ultra low-noise and hum
High-pass filter , allow selection of flat, 35 Hz or 75Hz, protect speakers and prevent speaker transformer saturation
with minimal effect on program material.
DIP switch control for clip limit, high-pass filter, bridge-mono stereo selections
AUTO variable- speed-low-noise fans ensure high reliability even under demanding conditions.
Detachable Euroblock: " Barrier strip" input connectors.
Rugged amplifier in a strong, compact chassis
1. INTRODUCTION
- 1 -

BRIDGE MODE:
8ohms,1kHz,0.1%THD (EIAJ) 4×500W
Distortion(SMPTE-IM) <0.05%
MONO MODE:
8 ohms per channel(EIAJ) 8x180WOutput Power
(20Hz 20kHz THD @ 0.1%) 4 ohms per channel(EIAJ) 8x250W
Frequency Response 20Hz-20kHz 1dB, -3dBpoint: 10Hz-60kHz
Damping Factor,1kHz,0.1%THD(EIAJ) >300@8ohms
Signal to Noise,20Hz-20kHz 90dB
Voltage Gain 40×( 32dB)
Input sensitivity@ 4 ohms 1Vrms
Input clipping 10Vrms(+22dB)
Input impedance 10K ohms unbalanced, 20Kohms balanced
Front: AC Switch, Ch1-Ch8 Gain Knobs
Controls Rear: MODE SWITCHES
Power-On: Blue LED
Protection: Red LED
Signal: LED Green
Clip: Red LED
Parallel-input: Yellow LED
Indicators
Bridge: Yellow LED
Input: Terminal Block
Connectors, each channel Output: Screw-terminal Barrier Block
cooling Continuously variable-speed fan, front-to- rear airflow
Load protection On/Off muting, overheat & short circuit protection
Power supply 220-240(110-120)Vac50-60Hz
Dimensions 17.7"(44.95cm)(D)*3.5"(8.9cm)(H)*19.02"(48.3cm)(L)
Net weight 21.6Kg
2. TECHNICAL SPECIFICATION
- 2 -

1 2 3 4 5 6 78
A B C D
8
7654321
D
C B A
BREAKER
CH1,2,3,4 FAN PS
BRIDGE
CH1,2,3,4 RELAY PS
BRIDGE
G1 G2
PS1 BRIDGE
PS2
BRIDGE
PS3
BRIDGE
PS4
BRIDGE
PS5
BRIDGE
PS6
BRIDGE
PS7
BRIDGE
PS8
BRIDGE
&+ &+ &+ &+ &+ &+ &+ &+
OUTPUT1 OUTPUT2 OUTPUT3 OUTPUT4 OUTPUT5 OUTPUT6 OUTPUT7 OUTPUT8
CH5,6,7,8 FAN PS
BRIDGE
CH5,6,7,8 RELAY PS
BRIDGE
G3 G4
9 99 9
1 2 3
CH1
INPUT


CH1
LEVER
&/,3
/,0,7(5
CH1,2,3,4
Heat Protection
+24V
RELAY
&+$03
1 2 3
CH2
INPUT


CH2
LEVER
&/,3
/,0,7(5
&+$03
1 2 3 4
CH1,2
OUTPUT




CH1
SPEAKER
CH2
SPEAKER
BRIDGE1 SPEAKER
1 2 3
CH3
INPUT


CH3
LEVER
&/,3
/,0,7(5
RELAY
&+$03
1 2 3
CH4
INPUT


CH4
LEVER
&/,3
/,0,7(5
&+$03
1 2 3 4
CH3,4
OUTPUT




CH3
SPEAKER
CH4
SPEAKER
BRIDGE2 SPEAKER
1 2 3
CH5
INPUT


CH5
LEVER
&/,3
/,0,7(5
RELAY
&+$03
1 2 3
CH6
INPUT


CH6
LEVER
&/,3
/,0,7(5
&+$03
1 2 3 4
CH5,6
OUTPUT




CH5
SPEAKER
CH6
SPEAKER
BRIDGE3 SPEAKER
1 2 3
CH7
INPUT


CH7
LEVER
&/,3
/,0,7(5
CH5,6,7,8
Heat Protection
+24V
RELAY
&+$03
1 2 3
CH8
INPUT


CH8
LEVER
&/,3
/,0,7(5
&+$03
1 2 3 4
CH7,8
OUTPUT




CH7
SPEAKER
CH8
SPEAKER
BRIDGE4 SPEAKER
POWER SWITCH
CH5,6,7,8
Heat Protection
+24V
CH1,2,3,4
Heat Protection
+24V
35/75Hz FILTER
35/75Hz FILTER
35/75Hz FILTER
35/75Hz FILTER
35/75Hz FILTER
35/75Hz FILTER
35/75Hz FILTER
35/75Hz FILTER
PT-MC250.8
3. BLOCK DIAGRAM
- 3 -

1 2 3 4 5 6 78
A B C D
8
7654321
D
C B A
R1_12 22R 2W
R1_14 0.1R 3W
Q1_2 2SA1943
D1_3
1N4148
+60V_A
D1_11 1N4004
Q1_1
C4382
R1_37
500R 3W
C1_16
22nF/100V poly
C1_14 3.3nF/50 cer
C1_15
3.3nF/50 cer
R1_36 4R7
R1_35
4R7
GND1
D1_5
1N4148
Q1_6
A1668
D1_4
1N4148
Q1_7 2SC5200
R1_13 22R 2W
R1_15 0.1R 3W
GND1
-60V_A
D1_13 1N4004
D1_15
1N4937
D1_14
1N4937
C1_13
2.2nF/50 cer
C1_12
22nF/50 cer
D1_9
ZD3V9 1/2W
R1_9 820R
R1_7 2K 3W
R1_10 820R
R1_8 3K 2W
D1_10
ZD3V9 1/2W
D1_6
1N4148
Vic1+
D1_7
ZD15V1W
C1_2
220uF/25V
GND1
R1_18 100R
GND1
Vic1-
C1_11
56pF/50 cer
R1_21
10K
C1_23
27pF/50 cer
R1_43
12K
R1_29
330R
GND1
GND1
CH1 GAIN
C1_9
47uF/25V
D1_8
ZD15V1W
C1_3
220uF/25V
GND1
C1_6
100pF/50 cer
C1_10
47uF/25V
C1_7
100pF/50
C1_21
10uF/25V
GND1
C1_20
10uF/25V
R1_31
NTC 500R
3 2
1
U1_1A
NJM4580L
5 6
7
U1_1B
NJM4580L
84
U1_2C
NJM4580L
Vic1+
Vic1-
1 2 3
CN1_20
2.54 3P
5 6
7
U1_2B
NJM4580L
R1_1 4K7
R1_2 4K7
D1_1
DB107G
GND1
R1_5 47R
AK
2 1
U1_3
VTL5C2
GND1
(FTR VT90N1 VACTEC+)
GND1
1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 18 19 20
J1_6
HEADER 10X2
GND1 GND1
L1_1
2uH 10A
R1_40 5R6 2W
R1_41
10R 3W
C1_17
100nF/250V poly
GND1
SP-1+
SP-1-
CH1 PHOTO COUPLER
-15V
+15V
GND1
R1_44
10K5
R1_34 300R
R1_33 300R
C1_29
331
0.2A
0.2A
84
U1_1C
NJM4580L
R1_25 10K
R1_22 10K R1_23 10K
R1_24 10K
CH1 PROT
R1_52 56K
D1_17
ZD5.6V 1W
R1_49 120K
R1_47
47K
Q1_8 MPSA42
GND1
D1_2
DB107G
CH2-AMP MC8AMP-CH2.SCH
Vic1+
Vic1-
3 2
1
U1_2A
NJM4580L
C1_5
0.047uF/50 cer
C1_4
0.22uF/50 cer
C1_8
0.1uF/50 cer
R1_16 4K75
R1_19 15K
R1_17 47K5
TP1_1 TP-2
1 2 3 4 5 6 7 8 910 11 12 13 14 15 16
J1_5 HEADER 8X2
R1_3 16K
R1_4 16K
CLIP
LIMITER
CH2 PROT
R1_46
22K
C1_26
100uF/16V
D1_12
1N4004
J1_2 TP-2 J1_1 TP-2
BRD1-LED- BRD1-LED+
PROT1-LED+ PROT2-LED+
PROT1-LED- PROT2-LED-
PAR1-LED+PAR1-LED-
SIG1-LED+ SIG2-LED+
CLIP1-LED+CLIP1-LED-
CLIP2-LED- CLIP2-LED+
CH1-75Hz
CH2-FILTER
CH2-75Hz
CH2-LIM-1 CH2-LIM-2
CH2-IN+
CH2-IN-
BRD1-SW
CH1-FILTER
CH1-35Hz CH2-35Hz
PAR1-SW
CH1-IN+
CH1-IN-
CH1-LIM-1 CH1-LIM-2
SIG2-LED+
CLIP1-LED+
CLIP1-LED-
CH1-75Hz
CH1-FILTER
CH1-35Hz
CH1-IN+
CH1-IN-
CH1-LIM-1
CH1-LIM-2
CH3-AMP MC8AMP-CH3.SCH CH4-AMP MC8AMP-CH4.SCH
K1_1
MI-SH-224L
SP-2+
J1_3 TP-2
OUT2
GND1
Q1_3 A684
R1_26 15R
GND1
TR1_1 MPSA42
TR1_2 MPSA92
R1_27 1.8k
R1_30 680R
R1_28 330R
R1_32 47K
GND1
Q1_5 C1815
TR1_3 MPSA42
C1_24
47uF/25V
R1_39 330K
R1_48 47K
PRO 2
R1_38 330K
1
2
3
U1_4 LM317T
1 2
R1_53 1K8 C1_28
100nF/50V
C1_25
10uF/50V
1 2
CN1_6 2P-2.5
G1
1 2
CN1_5 2P-3.9
G1
C1_27 470u/35V
1 2
CN1_4 CON2
R1_45 68K
G1
G1
R1_6
0R
R1_54
NTC500R
D1_16
DB107G
GND1
1 2
CN1_3 2.54 2P
C1_18
220UF/25V
C1_19
0.1uF/50V
GND1
GND1
BD1 250v2A
+60V_A
-60V_A
V1+
V1-
GND1
1 2 3
CN1_1 CON3
OUTPUT_1
OUTPUT_1
CH1-2 BRIDGE
D1_18 1N4004
R1_55 1K-1W
SIG1-LED+
R1_51 1K-1W
C1_30
331
GND1
R1_56 22K
Q1_9 MPSA42
C1_31
47uF/25V
TR1_4 MPSA42
SW101 95C
RELAY PS
TP SW
72&+
72&+
PRO 1
PRO 1
R1_60 1K
R1_61 3.3K
R1_62 3.3K
0&$03
PWR ON LED
4. SCHEMATIC DIAGRAM
- 4 -

- 5 -

- 6 -

- 7 -

1234
A
B C D
4
3
2
1
D
C B
A
LD1_2 RED
LD1_1 GR
LD1_3 YEL
LD1_4 YEL
LD2_1 GR
LD2_3 YEL
LD2_4 YEL
LD2_2 RED
CLIPPROT LIMIT PAR BRDG LIMIT CLIP
12
3
4
56
78
910
11 12
13
14
15 16
J1HEADER 8X2
LD3_2 RED
LD3_1 GR
LD3_3 YEL
LD3_4 YEL
LD4_1 GR
LD4_3 YEL
LD4_4 YEL
LD4_2 RED
CLIP LIMIT PAR BRDG LIMIT CLIP
12
34
5
6
7
8
9
10
11
12
13
14
15
16
J2HEADER 8X2
PROT
PROT PROT
/('6FKHPDWLF
- 8 -

1 2 3 4 5 6 78
A B C D
8
7654321
D
C B A
1 2
CN1 CON2
1 2 3 4 5 6 7 8
CN10 CON8
1 2 3 4 5 6 7 8
CN11 CON8
CH1 OUTPUT CH2 OUTPUT CH3 OUTPUT CH4 OUTPUT CH5 OUTPUT CH6 OUTPUT CH7 OUTPUT CH8 OUTPUT
CH1- CH2- CH3- CH4-
CH5- CH6- CH7- CH8-
- - + + - - + + - - + + - - + +
CH1+ CH2+ CH3+ CH4+
CH5+ CH6+ CH7+ CH8+
1 2
CN2 CON2
1 2
CN4 CON2
1 2
CN3 CON2
1 2
CN5 CON2
1 2
CN6 CON2
1 2
CN8 CON2
1 2
CN7 CON2
1
2
3
CN7
1
2
3
CN8
1
2
3
CN5
1
2
3
CN6
GND1 GND1
CH1_IN+ CH2_IN+ CH1_IN- CH2_IN-
CH1_IN+ CH1_IN-
CH2_IN+ CH2_IN-
CH2 BRIDGE CH1_LIM_SW1 CH1_LIM_SW2
CH2_LIM_SW1 CH2_LIM_SW2
GND2 GND2
CH3_IN+ CH4_IN+ CH3_IN- CH4_IN-
CH3_IN+ CH3_IN-
CH4_IN+ CH4_IN-
CH4 BRIDGE CH3_LIM_SW1 CH3_LIM_SW2
CH4_LIM_SW1 CH4_LIM_SW2
1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 18 19 20
CN22
HEADER 10X2
1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 18 19 20
CN21
HEADER 10X2
GND1 GND1
CH1_IN+ CH1_IN-
CH2_IN+ CH2_IN-
CH2 BRIDGE
CH1_LIM_SW1 CH1_LIM_SW2
CH2_LIM_SW1 CH2_LIM_SW2
CH1-FILTER
CH1-FILTER35HzCH1-FILTER75Hz
CH2-FILTER75Hz CH2-FILTER35Hz CH2-FILTER
GND1 GND2
CH1-FILTER CH1-FILTER35Hz CH1-FILTER75Hz
CH2-FILTER75HzCH2-FILTER35Hz CH2-FILTER
CH1/2-PAR_LED
CH1/2-PAR_LED
GND2 GND2
CH3_IN+ CH3_IN-
CH4_IN+ CH4_IN-
CH4 BRIDGE
CH3_LIM_SW1 CH3_LIM_SW2
CH4_LIM_SW1 CH4_LIM_SW2
CH3-FILTER CH3-FILTER35Hz CH3-FILTER75Hz
CH4-FILTER75HzCH4-FILTER35Hz CH4-FILTER
CH3/4-PAR_LED
CH3-FILTER
CH3-FILTER35HzCH3-FILTER75Hz
CH4-FILTER75Hz CH4-FILTER35Hz CH4-FILTER CH3/4-PAR_LED
1
2
3
CN3
1
2
3
CN4
1
2
3
CN1
1
2
3
CN2
GND3 GND3
CH5_IN+ CH6_IN+ CH5_IN- CH6_IN-
CH5_IN+ CH5_IN-
CH6_IN+ CH6_IN-
CH6 BRIDGE CH5_LIM_SW1 CH5_LIM_SW2
CH6_LIM_SW1 CH6_LIM_SW2
GND4 GND4
CH7_IN+ CH8_IN+ CH7_IN- CH8_IN-
CH7_IN+ CH7_IN-
CH8_IN+ CH8_IN-
CH8 BRIDGE CH7_LIM_SW1 CH7_LIM_SW2
CH8_LIM_SW1 CH8_LIM_SW2
1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 18 19 20
CN20
HEADER 10X2
1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 18 19 20
CN6 HEADER 10X2
GND3 GND3
CH5_IN+ CH5_IN-
CH6_IN+ CH6_IN-
CH6 BRIDGE
CH5_LIM_SW1 CH5_LIM_SW2
CH6_LIM_SW1 CH6_LIM_SW2
CH5-FILTER
CH5-FILTER35HzCH5-FILTER75Hz
CH6-FILTER75Hz CH6-FILTER35Hz CH6-FILTER
GND3 GND4
CH5-FILTER CH5-FILTER35Hz CH5-FILTER75Hz
CH6-FILTER75HzCH6-FILTER35Hz CH6-FILTER
CH5/6-PAR_LED
CH5/6-PAR_LED
GND4 GND4
CH7_IN+ CH7_IN-
CH8_IN+ CH8_IN-
CH8 BRIDGE
CH7_LIM_SW1 CH7_LIM_SW2
CH8_LIM_SW1 CH8_LIM_SW2
CH7-FILTER CH7-FILTER35Hz CH7-FILTER75Hz
CH8-FILTER75HzCH8-FILTER35Hz CH8-FILTER
CH7/8-PAR_LED
CH7-FILTER
CH7-FILTER35HzCH7-FILTER75Hz
CH8-FILTER75Hz CH8-FILTER35Hz CH8-FILTER CH7/8-PAR_LED
1.CLIP LIMIT-CH1 10.CLIP LIMIT-CH2 3.FILTER_FEQ-CH1 8.FILTER_FEQ-CH2 2.FILTER-ON/OFF-CH1 9.FILTER-ON/OFF-CH2 4.PARALLEL+ 5.PARALLEL- 6.PARALLEL-LED 7.BRIDGE ON/OFF MODE SWITCH SETTINGS
1 2 3 4 5 6 7 8 9
10 11
12 13 14 15 16 17 18 19 20
ON
12345678910
SW2 DIP10
1 2 3 4 5 6 7 8 9
10 11
12 13 14 15 16 17 18 19 20
ON
12345678910
SW1 DIP10
1 2 3 4 5 6 7 8 9
10 11
12 13 14 15 16 17 18 19 20
ON
12345678910
SW3 DIP10
1 2 3 4 5 6 7 8 9
10 11
12 13 14 15 16 17 18 19 20
ON
12345678910
SW4 DIP10
,1387287387
BRIDGE PIN6(+)~PIN7(-)
BRIDGE PIN2(+)~PIN3(-)
BRIDGE PIN2(+)~PIN3(-)
BRIDGE PIN6(+)~PIN7(-)
-
9
-

- 10 -

1234
A
B C D
4
3
2
1
D
C B
A
VR1 A10K
1
2
3
CN1 3P2.5
VR2 A10K
1
2
3
CN2 3P2.5
CH1 CH2
VR3 A10K
1
2
3
CN3 3P2.5
VR4 A10K
1
2
3
CN4 3P2.5
CH3 CH4
VR5 A10K
1
2
3
CN5 3P2.5
VR6 A10K
1
2
3
CN6 3P2.5
CH5 CH6
VR7 A10K
1
2
3
CN7 3P2.5
VR8 A10K
1
2
3
CN8 3P2.5
CH7 CH8
956FKHPDWLF
- 11 -

12345678
A B C D
8
7654321
D
C B A
TRANSFORMER
R1
NP35L-Y2
R2
NP35L-Y2
POWER SWITCH
15A REAKER
C49
0.1uF/275V X2
230V 50Hz
AC IN
P1
P4 P5
P2 P3
P6 P7 P8
HB01869
Power Supply
HB01868
Amplifier CH1~CH4
HB01868
Amplifier CH5~CH8
HB01864
INPUT+OUTPUT
1
2
3
4
5
6
CN1
1
2
3
4
5
6
CN2
1
2
3
4
5
6
CN3
1
2
3
4
5
6
CN4
Volume Control
&+&+'LVSOD\
FAN FAN FAN FAN
1 2
CN15
1 2
CN16
1 2
CN17
1 2
CN18
1 2
CN1_5
1 2
CN1_3
1 2
CN1_5
1 2
CN1_3
*5((16+257
<(//2:6+257 *5((1/21* <(//2:/21*
1
2
CN1_16
1
2
CN1_6
1 2
CN1_4
Power ON/OFF LED
BLUE
1
2
CN1_16
1
2
CN1_6
+60V_A
-60V_A +60V_B -60V_B J1_2 J2_2
+60V_C
-60V_C +60V_D -60V_D J3_2 J4_2
+60V_A
-60V_A +60V_B -60V_B J1_2 J2_2
+60V_C
-60V_C +60V_D -60V_D J3_2 J4_2
1
2
3
4
5
6
CN5
1
2
3
4
5
6
CN6
1
2
3
4
5
6
CN7
1
2
3
4
5
6
CN8
CH1OUT
CH1GND
CH2OUT
CH2GND
CH3OUT
CH3GND
CH4OUT
CH4GND
CH8OUT
CH8GND
CH7OUT
CH7GND
CH6OUT
CH6GND
CH5OUT
CH5GND
1 2
CN11
1 2
CN12
1 2
CN13
1 2
CN14
J1 J2 J1 J2
+.
J1_7
J3_4
J1_6 J3_6
J1_7
J3_4
J1_6 J3_6
J19J20J21J22
1
2
3
CN1
1
2
3
CN2
1
2
3
CN3
1
2
3
CN4
1
2
3
CN5
1
2
3
CN6
1
2
3
CN7
1
2
3
CN8
1 2 3
CN1_20
1 2 3
CN2_25
1 2 3
CN3_19
1 2 3
CN4_20
1 2 3
CN1_20
1 2 3
CN2_25
1 2 3
CN3_19
1 2 3
CN4_20
+.
&+&+'LVSOD\ &+&+'LVSOD\
+.
&+&+'LVSOD\
'LVSOD \
'LVSOD \'LVSOD \
'LVSOD \
5. WIRING DIAGRAM
- 12 -


󲓱
󲓱 󲓱 󲓱 󲓱 
󲓱
󲓱 󲓱

󲓱
󲓱 󲓱 󲓱 󲓱 󲓱 󲓱 󲓱
6. PCB LAYOUT
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


󲓱
- 14 -


󲓱
󲓱 󲓱 󲓱 󲓱 
󲓱
󲓱 󲓱

󲓱
󲓱 󲓱 󲓱 󲓱 󲓱 󲓱 󲓱
- 15 -

 󲓱
- 16 -


󲓱
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The Finished Products Test
Test instruments
1). VF analyzer
2). Multimeter
3). Frequency transformer
4). 4Ω（1000W）load resistance*2PCS
5). 8Ω（1000W）load resistance*2PCS
6). Oscilloscope
7). AC protector
1. Initialize:
1) The Power switch turns OFF.
2) Connect the Power cord to AC protector.
3) The Output of frequency converter is 230V/50Hz; turn off all the push
switches.
2. Turn on the Power switch, the blue power LED and PROT LED will
illuminate, and other LEDs don’t illuminate, 2~5 seconds after turning on the
unit, the PROT LED will extinguish.
3. Mono Channel Output Test: With 4Ωloads at the Output terminal, input
1KHz/0.6dBu±0.25dBu signal, then rotate corresponding VRs to maximum,
the output will reach to 207W±5W, at this time, the distortion should be less
than 1%. The S/N of CH1 should be higher than 85dB, and the S/N of other
channels should be higher than 90dB. When rotating the VR from minimum
to maximum, with the increase of VR, the SIG LED will become
well-illuminated, when the power is full, the CLIP LED illuminates slightly,
and the output waveform will appear cut-off distortion.
4. LIMITER Test: Go on the step 3, when the “1”of push switch is at the “ON”
position, the CLIP LED extinguishes, the output power will drop to
190W±5W, the distortion should be less than 1%(When test the LIMIT CLIP,
set “1”(on push switch)of the CH1/CH3/CH5/CH7 to “ON” position, set
“10”(on push switch)of CH2/CH4/CH6/CH8 to “ON” position). When doing
the third and fourth step test, the post can not appear protection
phenomenon.
5. Short Circuit Protection Test: When full power output, the short circuit output
terminal and the post relay should open within 1~ 7 seconds and also should
close 1~3 seconds later, the PROT LED and CLIP LED will change with the
relay from brightly to extinguish.
6. Noise Test: Connect a 4Ωload, and set the VR to maximum, the Hum or
7. TEST PROCEDURE
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