Precautions Before Servicing; Precautions For Measuring Of The Output Waveforms - Technics SX-PX554 Service Manual

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PCB
Wave ROM check
MAIN
MAIN: IC12, IC18
Control Panel buttons
CPL
LED lighting check
CPR
Control Panel LED
display check
Keyboard ROM (IC1)
MKB
check

9. PRECAUTIONS BEFORE SERVICING

9.1. Precautions for measuring of the output waveforms

1. The waveform was measured with a "National Digital Storage
TEST MODE
1. Press and hold the two E keys shown below, and then turn on the power switch.
2. Select the POP GROUND sound.
3. Reduce the MAIN VOLUME level low enough.
When set to the self-diagnostic mode, the Wave ROM outputs a sine wa
The Wave ROMs correspond to the keyboard keys as shown in the
diagram to the right. When a key is pressed, the corresponding sine wa
sound is produced. If no sound is produced, or if the sound is distorted
the Wave ROM corresponding to that key is defective. This method allo
to diagnose also the output routes (L/R) from the Wave ROM.
-
The key number indicates the Wave ROM number.
(I-1: IC12, I-2: IC18)
Press and hold the two F keys shown below, and then turn on the powe
switch.
Press the buttons on the control and confirm that the corresponding LE
light.
Press and hold the two G keys shown below, and then turn on the powe
switch.
The numbers are displayed automatically and repeatedly on the display
Press and hold the two A keys shown below, and then turn on the powe
switch.
If the keyboard ROM (IC1) is OK, only the TOUCH SENSITIVITY LIGHT L
flashes. If it is defective, the LEDs (LIGHT and NORMAL, or LIGHT,
NORMAL and HEAVY) flash.
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Procedure