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Sound Board
The Sound Board produces al l of the mus ic,sou nd, and speechfor the game .
Microprocessor (UtS)
The Sound Board uses the same microprocessor as the CPU board to control and process data .
Using an oscilloscope the address and data lines should be square waves, at least 4V peak -to-peak.
the lines that are not pulsing should generally be "low" .
The microprocessor runs on an 5Mbz clockcircuit supplied by Xl and U23 to pins 34 and 35.
RAM(U9)
The 2064 RAM provides temporary memory storage for the microprocessor.
ROMs (Ut4, U15, UlS)
The Sound Board uses 2 or 3 (depends on the game) 1MROMs. It is neces saryfor UlS to be used all
the time. U14 and U15 are used either individually along with UIS, or together along with UIS.
Music Circuit (UIO,
un,
US)
The Music Circuit produces the games' music. This circuit consists of UIO a YM2151 Sound
Generator, U11 a YM30I2
D/A,
and US a TL084 Op Amp. Music data is fed to UI0. UI0, which
functions as a smaller processor, sends this information to Ull in digita l format . Ull converts
this digital music date into an analog format. The analog output is seen on pins 9 to 12 as sine
waves about 2V peak-to peak riding around ground. Th is output is sent to US where it is amplified .
DACCircuit
(VI9,
U32)
The DAC Circuit produces the standard game sounds (anything that is not speech or music ). The
DAC ,U19 , gets its information in digital format, converts it into an analog format and sends the
data to U32 where it is amplified. The output waveforms from UI9 on pins 1, 2, 15 and 16 should be
at least +3V peak.
Speech Circuit (U25, U17)
The Speech Circuit produces speech . Speech data is fed to U25 and then to UI7. The output ofU17 is
pin 3 and should be a square wave about I V to 2Vpeak -to-peak,riding on about +2 .5V.
Mixer Circuit (U7,
VB)
The Mixer Circuit takes the outputs from the Sound ,DAC and Speech Circuits and mixes them
together. The mixed sounds are sent to U2, a MC3340 Attenuator which controls the volume. The
signal is then passed to UI , a Power Amp which amplifies the sounds before being sent to the
speakers .
Power
Circuit
The +5V is supplied by the Power Driver Board and comes to the Sound Board from J502. The ±12V
is supplied by the Sound Board itself. AC is supplied by the transformer to J50I of the Sound Board.
DI, D2, D3, and D4 convert the AC to unregulated DC .At the anode of Dl and 04 is about -30V
unregulated DC. At the cathode of02 ·and D3 is about +30Vunregulated DC. U3 and U4 are LM7912
Voltage Regulators .U3 regulates the -30Vto about ~12V ,wh ileU4 regulate sthe +30Vto about +12V .
Sound Board Beep Error Codes Upon Game Turn-On:
1 Bee p
""
SoundBoard O.K.
2
Beeps
=
V9
Fai lure
(RAM)
3 Beeps
=
VIS
Fa ilure
(ROM)
4 Beeps
=
VI5 Fail ure (ROM)
5 Beeps
=
V14 Failure (ROM)
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