Casio DH500 Troubleshooting guide

J
)I
I
ISERvrcE MANuAL
& PARTS LIST (w,hprce)
trligital Horn
DH-5[j0
MAY 1989
GASilO.
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CONTENTS

SCHEMANC
DIAGRAM
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PCBVIEW& MAJOR
CHECKPOINTS
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@ Pitch
sQnat
PC6
lC13
pin
17
Tone:
Saxophone,
No
key
press
Sampling
Clrcuit
Input
lC7 pin 1
Tone: Saxoptibne,
Nokeypress
SamplingClrcuitoutput
lC7 pin 7
Tone:Saxophone,
Nokeypress
t tt\
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@
$ffitln
:'L',:!'.
TnfiarOboe;'
Nokey
press
@ p^lf"ol.e/To6
ciibuitoiiipil' ,,
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t ,
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ICBpin
1
Tone: Saxophone, Nci
keypiussi
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t
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MAJOR WAVEFORM
@
o
@
o
@
o
Reset
s'tgnal
lCl4pln
6
Al Power
ON
Pilch
slgnal
PC6
1c13,
pin
t7
Tone:
Obo€,
Nokeyprsss
A 5pa
rAC
;
cxr .
aV orl
Rpverb
Mute
sQnaf
lC
13 pln
15
ATPower
ON
@ vcF
ouqrr
l0l1 pin I
Tone: Saxophone,
Nokeypress
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BLOCK
DIAGRAM
MainVolume
o
@
o
@
o
@
@
Orlginal
sound
Sample/
Hold
Circuit
PF4,PF6,PF7
o
BSHH DlgilalS[nal Processor
M8661131
i
I
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.t
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.:
Breath
Sensor
blockoutputs
voltage
whlchconesponds
tothestrength
ofbreath.
Uslngabuilt-ln
ADC
(Analog
loDigitalConverter), theCPU
digitizesthe
voltagelevellrom
Breath
Sensor
and
outputs
thedigitized
data
P0-P7
lo DAC
(Digital
toAnalog Converter)
1.
On
theother
hand,CPU
detects
pressed
keys
and
provides
conesponding
sound
slgnalPC6.
Thesound
signal
is amplifiedandlilteredinVCA(Voltage
Controlled
Amplifier)
and
VCF
(Voltage
Controlled
Fllter)whose
anplitudeandcutoff
frequency
depend
uponcontrolvoltagefrom
DAC1.
DAC1
converts
the
digitlzed
dataP0-P7intoa
voltage
levelwhich
becomescontrol.vg$ggflf
VCAand
VCF.
Thus,
the gound ouput PC-6's
volume
andcutotf
frequeLcJt_g19_-vadeilln
accoi&n-cewiththe
slrength
ofthebreath.
VCF
outprt
lsdigitizedinDSP
(D(;ital
Signal
Processor)
andstored
in
theHAM.
Changing
the
reading
speed
olRAM
dala,
thesounddatais
delayed,
DAC'd,llllered,
ardmixedwith the
orlginalsound
inMlxer.
CPU
pPD78C1lG

DISASSEMBLY
& CHECKING
N'ETHOD
Rernove
seven
screws
from
bottom
case-
Remove
the
mouthpieth
and
open
the
top
case
fnsert
asilbon
rubber
tube
(code
No.
6914
7972)
in
mouthplece
and
set
themouthpiece
on
bottom
cover.
waveforms
can
be
observedwith
oscilloscope
by
btowiqg
the
lube.
1
t nir
\
b
b
bO
@
@
@
See
Fag- th6 7+
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