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TESTJDIAGNOSTIC PROCEDURES (Continued)
SYSTEM-11A SOUND CIRCUITRY TESTS (Continued)
If no sound is heard, refer to the text entitled "NO SOUND ...". If ~ "ring" is heard, this indicates
a
malfunction of the U23 RAM Chip. If either OOQ. or 12!.!.!: "rings" is heard, this indicates a problem
associated with the U21
ROM
Chip.
If
either ~ or five "rings" is heard, this indicates
a
problem
with the U22 ROM Chip.
NO SOUND DURING THIS TEST
(but sound can be heard during the Diagnostic Tests).
Check the sound-select inputs (pins 2 through 9 of U9) to see if they pulse during Sound Test
01. Also, check the -12 V supply
votaqe
on the CPU Board.
If
this voltage is low (or AC ripple
seems too high), perform the following checks:
1. The gray and gray-green transformer secondary wires for 19.4 VAC.
2. The CPU Board filter capacitor C26 for -12 VOC.
3.
The filter capacitor C26 for excessive AC ripple (over 0.75VAC).
If
the previous checks did not isolate the problem, turn the Volume Control for maximum output.
Momentarily touch a powered-up AC soldering pencil on the center tap of the Volume Control.
©~I!.!TTIIl@OO
DO NOT use a soldering iron over 40 watts. Note also that cordless soldering
irons will NOT work for this test.
Hearing a low hum indicates that the power amplifier (U1, TDA2002), the Volume Control, and the
speaker are operating satisfactorily, as is the sound circuit cabling. Not hearing a hum requires re-
peating the test with the Volume Control turned part way down, to determine whether the Volume
Control is faulty. Also, check the cable connectors for proper mating, and that no broken wires
affect this circuit.
FUSE LISTING.
The following fuses are used:
Part Number
Circuit/Location
Input Power ("high voltage"} Line/Cabinet Box"
Gen.
Illumination/Upper Rt Backbox fuseholder (4)
+
18 VDC Lamp CkV Lwr Rt Backbox fuse holder (1)
+ & - 100V Display Pwr/Upr Cntr B'box fuseholder (2)
F1 - F6; 0-11813 Aux Pwr Driver Board
F7, F8; 0-11813 Aux Pwr Driver Board
F1, 0-8345-557 Power Supply
F5, F6; D-8345-557 Power Supply
Description
5730-09252-00 Fuse, SA Slow-Blow (S-B).
125v
5731-09651-00 Fuse, SA SoB,
250v
5730-09071-00 Fuse, SA S-8,
32v
5730-12203-00 Fuse, 1/10A SoB, 250v
5731-08665-00 Fuse, 2A S-8,
250v
5731-06314-00 Fuse, 4A S-8,
250v
5731-08761-00 Fuse, 1/4AS-B,
250v
5731-09432-00 Fuse, 7A SoB, 250v
• One 4A SoB, 250v fuse (5731-06314-00) is provided for an overseas
(220v)
game installation.
BIG GUNS
33