Korg POLY-61 - 8. CHECK AND ADJUSTMENT PROCEDURE; Power Supply, Clock Board, and Joystick Checks

8. CHECK AND ADJUSTMENT PROCEDURE
Caution: Everything has been completely adjusted at the factory prior to shipment. Therefore, never turn any VRs other
than those required for servicing.
* After turning on power, wait at least ten minutes before beginning tests and adjustments.
* Circuit board numbers change from 711801 , as divided into new production and old production lots.
Old circuit board numbers are in parentheses.
* If replacing KLM-508 (KLM-476) ICs 101~601 NJM072DH, be sure to use new ones of the same color selection. Others
will cause irregularities in sawtooth wave amplitude and PW/PWM duty.
* Adjustment setting charts are on a separate page. Please refer to it for correct settings.
* Data cassette (Data of adjustment procedure) showing the setting is available for repairing and adjusting. Please load the
cassette on and select a program you need each time.
1. KLM-480 (Power supply check and adjustment).
Use DVM (digital voltmeter) to test each check point on
KLM-480. Confirm that voltages are within specifications
listed below.
(1) +15V: +14.95V~+15.05V; Adjust VR1 if necessary.
(2) -15V: -14.70V~-15.30V
(3) +5V: +4.75V-+5.25V
2. KLM-477 (CLOCK BOARD check and adjustment).
1. TOTAL TUNE.
1) Set to PROGRAM 11.
2) Hold A3 (440Hz) and set TUNE knob to center.
3) Connect output to tuner and adjust VR5 to obtain
reading within ±5 cent.
4) Confirm +100 cent (±20 cent) when TUNE knob is
turned all the way clockwise (#).
5) Confirm —90 cent (±20 cent) when the TUNE knob
is turned all the way counterclockwise (b).
2. JOYSTICK.
1) Set to PROG RAM 11.
2) Hold A3 and adjust TUNE knob to obtain 0 cent
reading on tuner.
3) Set BEND knob to 10 and confirm +700 cent (0~+15
cent) (E above A3) when joystick is at maximum
pitch bend up position. Adjust VR6 if necessary.
4) Confirm -700 cent (-15~0 cent) (D) when joystick
is at maximum pitch bend down position. Adjust
VR7 if necessary.
5) Adjust TUNE knob to obtain 0 cent reading. Then
use joy stick to apply vibrato and pitch bends (up
and down), slowly returning the joystick to the
center position. Confirm that pitch is still within
±2 cent.
6) Connect oscilloscope to CN39—1, apply vibrato and
set FREQUENCY knob to 5. Confirm vibrato at
' rate of about 5~6Hz.
7) In same way, confirm about 10Hz when FRE¬
QUENCY knob is at 10, and about 0.12Hz when
knob is at 0.
8) Set FREQUENCY to 0 and apply vibrato at maxi¬
mum intensity.
Confirm tuner readout variation from +60~+120
cent to — 60~—120 cent. There should be no more
than 30 cent difference between the amount of swing
to the left and right.
3. K L M - 508 (KLM-478) (ANTI BOARD).
1. ANTI-LOG.
1) Set to PROGRAM 12 and put same note into
CHORD MEMORY six times. In other words, turn
on HOLD and play same note six times, then turn
on CHORD MEMORY.
Confirm that NJM-072 (IC101 —601) are all the same
color.
2) Check KLM-508 (KLM-476) (SYNTHE-BOARD) TP1
with DVM and confirm 9.80V~10.20V.
3) Connect oscilloscope GND to TPl and check TP102~
TP602.
Note: TPl is not at ground (0V).
4) Play Cl and confirm Fig-1 waveform for all six
voices.
5) N ext, expand oscilloscope range and check six voices,
finding the one with the greatest amplitude Fig-2 .
Confirm that difference between largest and smallest
amplitude is within 1.0V.
After finding voices with largest amplitude, perform
check and adjustment procedures A through I, below,
for that voice. (Adjust oscilloscope GND before¬
hand.)