Alto MAC 2.2, MAC 2.3, MAC 2.4, Service Manual

Page: 31 / 64

PCB test procedrue
(MAC2.4)
Wiring Diagram
7.3. PCB test procedure and specification
Refer to instrument (1) audio analysis 7724 (2) oscillograph (3) two load 4
Ω
(4) power source (5) DMM.
7.3.1 Without the signal input, to make DC voltage of R131 (MAC2.4-A)/R131 (MAC2.4) &R146 (MAC2.4-A), R246(MAC2.4-B)
by 0.09
±
0.01V.
7.3.2 Input signal of 1KHz 2dB to CH-A & CH-B, each output is more than 55V and the distortion less than 0.1%. (Stereo)
7.3.3 Input sine wave 1KHz 2dB, and then connect separately with 2
Ω
of load. Adjust the output of R139/R140(MAC2.4-A)
(MAC2.4-B) between 49.2
±
0.2V.
7.3.4 After heating the P.T.C. on the heat sink with a heat gun for 10 seconds. The fan should work more quickly. Heat P.T.C.
about 5 seconds more again, then the signal should be cut off automatically. (CHA, CHB)
7.3.5 Set the switch to PARALLEL, input signals from CHA, output should be from CHB
7.3.6 Set the switch to BRIDGE. Input signals from CHA. BRIDGE output should be more than 100V (8
Ω
).
7.3.7 Turn on the filter, then input 30Hz sine wave , output should attenuate 8.5
±
1dB. (CHA, CHB)
7.3.8 Turn on the LIMIT, input 6dB more, output distortion should be limited less than 3%. (CHA, CHB)
7.3.9 Without the signal input, test any one of R143 & R142, the voltage should be less than 60V(CHA); R243&R242, the
voltage less than 60V (CHB).
7.3.10 Set the volumes to minimum, set the output terminal of short circuit. When set the volume to maximum, the power
consumption should be less than 600W. (CHA, CHB)
Note: When MAC2.4-A is tested, do all the items above. When MAC2.4-B is tested, it is unnecessary to do item 5.
OSCILLATION
OUTPUT INPUT POWER
CH1
CH2
VP-7724A
POWER
88
88 88
8 88 8
8 88 8
8888
V
8888
A
110
NORL
SHORT
220
NORL
110V
220V
LOADSEL.
LOADOUT
LOAD S.P.
AC
UNSWITCH
DCIN
DCOUT
+
+
_
ADR-245
-
+
4 8 16
ACI NPUT
30