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TEST/DIAGNOSTIC PROCEDURES
(Continued)
SYSTEM-11 B SOUND CIRCUITRY TESTS.
Tests of the System-11B Sound circuitry, including the Audio Board, are possible only after
successful completion of the System-11B Memory Chip Test.
1 . Audio Board Test. A brief check of the Audio Board (0-11581) circuitry occurs at game
Turn-on; the game reports the test results by brief sounds, as follows: No sound
=
Audio
Board is not operating, or a failure is affecting the sound circuitry (broken cable; dead amplifier;
etc.); 1 sound
=
system OK; 2 sounds
=
RAM problem; 3 sounds
=
U4 problem; 4 sounds
=
U19 problem.
2 . General System-11 B Sound Test. Press the Sound Diagnostic Switch (SW 1) on left
edge of the CPU Board. Listen for the two test sounds, showing that both the CVSD (Continu-
ously Variable Slope Delta) Modulator, which provides the voices for
EARTHSHAKER,
and
the DAC (Digital-to-Analog Converter) sound circuits are functioning properly.
If no sound is heard, refer to the text entitled "NO SOUND ...". n
ana
"ring" is heard, this
indicates a malfunction of the U23 RAM Chip. If either
1WQ
or
f.Qw:
"rings" is heard, this indicates
a problem associated with the U21 ROM Chip. If either
tnraa
or
llil!l
"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 voltage 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 VDC.
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.
(g&'lUJ'ii'O@!NI
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 or a 'click' indicates that the power amplifier (U1, TOA2002), the Volume Con-
trol, and the speaker are operating satisfactorily, as is the sound circuit cabling. Not hearing a
sound requires repeating 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.
EARTH SHAKER 35