Adjust the knobs to the positions as listed below:
- Tone controls set to middle position.
- Faders up to maximum.
- Gain control knob turned to center position.
- Crossfader slided to center position.
- Volume control knobs VOL, VOL1 and VOL2 turned up to maximum.
- Input selector set to CD or LINE.
- PFL selector switched OFF.
Sensitivities:
- PHONO -40 dBV
- LINE -5 dBV
- CD +5 dBV
- MICRO (BAL) -50 dBV
- OUT 1 (BAL) 0 (+6) dBV
- OUT 2 (BAL) 0 dBV
- REC 0dBV
- HEADPHONES 230mW/400Ω
title:
VERIFICATION PROCESS
VERIFICATION
Turn on the mixing unit using the main switch. Verify that the green-coloured power-on
neon on the switch lights up, and also the mix-indicating LED does.
Apply a 1KHz +5dBV input signal to CD INPUT 1.
When all signal measurements are done on the REC output, verify that:
1.-VU-meter LED's are lit and display a 0dB level.
2.-The GAIN control is performing correctly, as its gain range should be ±15dB.
3.-The tone controls are correct (±12dB at 10KHz, ±15dB at 1'8KHz and ±12dB at
100Hz)
4.-Check the VOLUME control. At minimum, output signal should be cutted off; the
meter's displayed level depends on the output signal level. Leave the volume control at
position 10.
5.-Verify the Crossfader's functioning. When slided to the left, output level increases
up to maximum level. When slided to the right, output signal fades away and is cutted
off. Also the VU-meter should display the output signal evolution.
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6.-Press the PUNCH button (left), and verify that the output signal recovers a 0dB level.
Leave the crossfader at it's central position.
7.-Connect a set of headphones to the HEADPHONES jack-type output. Verify there is
signal indeed, and that when varying the headphone volume control knob, this output
signal is also altered. Leave this volume control turned up at maximum, and check that
when handling the channel volume control the headphone output signal is also altered.
Leave the channel volume control knob on position 10.
8.-Turn on the PFL selection switch. Now the channel volume control does not affect
nor the headphones level, nor the VU-meter displayed level, but does affect indeed the
REC output signal level.
9.-Switch the input selector over to PHONO. Verify the RIAA filter response curve
(+2dB at 100Hz, -24dB at 10KHz), level -40dB.
Repeat this whole procedure on channel 2, but take care about the performance of
crossfader and punch functions, as their functioning will be inverse as described for
channel 1.
Apply a -5dB level 1KHz signal to LINE INPUT3. From the listing above, repeat steps 1,
2, 3, 4, 7 and 8.
Change the input selector from LINE to MICRO.
Apply a -50dB 1KHz signal to the MICROPHONE jack-type input. Check that the REC
output signal level is 0dB.
Verify the two other outputs, OUT1 and OUT2, and their correspondent volume
controls. Notice that OUT1 is internally presetable to +6dB level.
To submit the unit to a burning test, leave it connected to the mains supply and turned
on for 24 hours.
SAFETY CHECKING TESTS
Before both tests:
Disconnect unit under test from mains.
Short-circuit and connect together to ground bolt/nut all inputs, outputs and all other
external connectors except mains plug.
Switch “GROUND LINK” to ON position.
Switch “POWER” to ON position.
Earth continuity test:
Connect earth tester between the mains connector ground pin and the ground bolt/nut
fitted at the unit chassis back plate. Apply a 10A current and verify that the earth path
has less than 0.1 ohm resistance.
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Dielectric strength test:
Connect the dielectric strength tester between mains input (both power lines shortcircuited) and the earth input pin from mains connector.
Adjust the current limit of tester to a 10mA value.
Apply a 1500Vac voltage during 5 sec.
The isolation may withstand this voltage without sparks or corona effects and thus, the
tester may not indicate fault condition.
WARNING: Do not remove or touch high voltage probes before test completion.
VERIFICATION USING MUSIC
Verify all signal in- and outputs with music. Verify that all signal controls are
functioning correctly, and that a good sound quality is obtained, noise- and distortionfree.
To ensure that all electrical junctions are well-fixed, hit the tested unit against your
working table, obviously without damaging its outer presentation; no crisperingor
annoying background noise should be added to the output signal due to this.
QUALITY CONTROL
All mechanical parts should be visually revised, in order to detect scratches on the
unit's painting; all screws should be on their place,correctly tight and unmarked. Check
out the unit's general presentation.