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VFX Article, Chapter 9
9. Hardware Checkout and Operation
Now we will perform a hardware checkout, one IC at a time. Remember
that ESD (Electro Static Discharge) precautions should be followed when handling these
ICs. This means - don't take the ICs out of their containers until you are ready to
install them in the sockets, grounding the Printed Circuit Boards and the container before
removing the parts. Don't walk around on carpet on a cold dry day waving the IC's in the
air. ESD can cause very subtle problems that can be hard to find. The kind that are worth
avoiding.
- First apply 9 VDC power to J1 and verify that there is 5 volts on the
power pins of each IC socket.
- When verified, remove power from the board and plug in U6, the
negative supply generator.
- Now reapply 9 VDC to J1 and measure pin 5 of U6. This voltage should
be the negative of the voltage on U6 pin 8 or 12 volts, whichever is less.
- Next, check pins 1 and 4 of U3. These should be -5.0 +/-.2 VDC and
+5.0 +/-.2 VDC respectively.
- Next, install the U1 (ADSP-2105), U2 (27256), U10 (74HC14) and U11
(CD4511) in their respective sockets. Set all the switches on SW1 to the "ON"
position and apply power to the board. The LED should display the number "6".
- Now install press the interrupt button and the LED display should
count very fast such that all LEDs appear to be dimly lit. This is the RAM test.
- Now remove power from the board and install the two RAM IC's. Apply
power to the board. The LED should again display "6".
- Then press the interrupt button and the LED should display
"0". If any RAM errors occur they will cause the display to increment.
- Next install the CODEC IC (National TP3054) and the audio amplifier
(National LM386). Connect your speaker or headphones to J2 and reapply power. Press the
interrupt button twice and a tone should be heard in the headphones.
- Finally install U4 (LM741), the input amplifier and connect your
microphone to J3. Apply power and press the interrupt button three times. Speak into the
microphone. Your voice should be heard through the microphones.
- Adjust the input potentiometer, (R50) and the output potentiometer
(R40) for minimum distortion.
- Now that your VFX board is working you can change the dip switches
for the other three effects as follows:
Dip Switch Settings
| |
SW1 |
SW2 |
SW3 |
SW4 |
| Harmonizer |
ON |
ON |
ON |
ON |
| Echo |
ON |
OFF |
ON |
ON |
| Reverb |
ON |
ON |
OFF |
ON |
| Test Mode |
ON |
OFF |
OFF |
ON |
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