Korg Poly-61 Service Manual page 21

shown in Fig-2 , or Fig-3 .
rm
iW,
re-
(A) Play C6 and adjust VR4 so that peak value
matches GND.
(B) Play A3 and adjust VR2 (VR1 (MID)) in same
way. ,, .
(C) Play Cl and adjust VR1 (VR2 (LOW)) in same
way.
(D) Repeat steps A "C above, as many times as
necessary so that deviation from GND is 0.1V
or less. .
(E) Set BEND knob to 10, play A3, and bend pitch
up and down using joystick. Adjust VR3 (BEND)
and VR4 (HIGH) to eliminate amplitude fluctua¬
tion during pitch bends. Confirm fluctuation of
0.1V or less.
(F) Repeat steps A~E to bring all values within
specifications.
(G) Play C6 and raise OCT (PARAMETER 11)
from 8' to 4'. Confirm peak value fluctuation of
within 0--0.2V at 8' and 0~-0.4V at 4'.
(H) At OCT 8' and 16', play each key in the lowest
octave of the keyboard and confirm that peak
value fluctuations are within +0.2V--0.4V.
Also confirm that LEDs on KLM-508 (KLM-476)
for voices 1 through 6 light up in correct order.
(|) Play C6 at 4' OCT and Cl at 16', Use joystick
for up and down pitch bends and confirm peak
value fluctuation within ±0.3V.
6) After completion, set to PROGRAM 12 again or
return parameter 11 (OCTAVE) to 16 .
_M-508 (KLM-476) (Old circuit board numbers
3
in parentheses.)
Amplitude limitation and 8253 RESET check.
1) Turn on ARPEGGIO switch; set FREQUENCY to
10, turn on LATCH, set RANGE to 10CT, and set
MODE to UP.
2) Play any three keys in the lowest octave and any
three in the highest octave; arpeggiate them.
3) Observe voice 1 at TP102 with oscilloscope, comfirm
sawtooth waveform maximum amplitude is about
12V, and that the waveform appears as in Fig-1.
4) Next, play C, and C6 arpeggiated.
5) Confirm that it is not as
6) Check and confirm in same way for voices 2~6.
7) Turn off CHORD MEMORY and switch to POLY
mode. (Turn off ARPEGGIO switch.)
2. DC01 check.
1) OCTAVE.
(1) Connect oscilloscope (IV/div, 2msec/div) to IC6
1-pin (IC3 1 PIN) and observe SIGNAL OUT wave¬
form. Confirm amplitude of about IV.
NOTE: Unless specified otherwise, SIGNAL OUT
tests should be performed at this same point in the
following instructions as well.
(2) Play C3 and confirm 6 voices.
(3) Switch PROGRAM number from 12 to 13 to 14
(easiest if using footswitch) and confirm OCTAVE
change from 16' to 8' to 4'. Also confirm no irregu¬
larities in sawtooth waveforms.
2) WAVEFORM
(1) Observe as above; Confirm 6 voices for C3 Key.
(2) Set to PROGRAM 15 and confirm change in wave¬
form from sawtooth to rectangle wave. Confirm
no irregularity in waveform.
(3) Confirm that rectangle waveform amplitude is
within ±15% of sawtooth waveform amplitude.
(4) Select PARAMETER 12 and switch VALUE be¬
tween 1 (K) and 2
(ID
while playing C6; confirm
no more than 1.5V DC fluctuation. Switch slowly
and confirm for all six voices.
19
Fig-1