Macro-Tech 600 Amplifier Service Manual
14
Electrical Checkout Procedures
Test 10: Slew Rate & 10 kHz Square Wave
Spec:
13 - 15 V/µS.
Initial Conditions:
Controls per standard.
Procedure:
Load each channel to 8 ohms. Inject a 10
kHz square wave to obtain 52 volts peak-to-peak at
each output. Observe the slope of the square wave. It
should typically measure 13 to 15 V/µS. Also, the
square wave must not include overshoot, ringing, or
any type of oscillation.
Test 11: Crosstalk
Spec:
-60dB at 20 kHz.
Initial Conditions:
Controls per standard. Terminate
input of channel not driven with 600 ohms.
Procedure:
8 ohm load on each channel. Inject a 20 kHz
sine wave into the Channel 1 input and increase output
level to 33 VAC. Measure less than 33 mVAC at the
output of Channel 2. Inject a 20 kHz sine wave into the
Channel 2 input and increase output level to 33 VAC.
Measure less than 33 mVAC at the output of Channel
1.
Test 12: Output Power
Spec at 8 Ohm Stereo:
>= 235W at 0.1% THD.
Spec at 4 Ohm Stereo:
>= 340W at 0.1% THD.
Spec at 2 Ohm Stereo:
>= 410W at 0.1% THD.
International 8 Ohm Stereo:
>=220W at 0.1% THD.
International 4 Ohm Stereo:
>=275W at 0.1% THD.
International 2 Ohm Stereo:
>=300W at 0.1% THD.
Initial Conditions:
Controls per standard.
Procedure:
Load each channel to 8 ohms. Inject a 1 kHz
sine wave and measure at least 43.36 VAC at the
output of each channel. Load each channel to 4 ohms.
Inject a 1 kHz sine wave and measure at least 36.88
VAC. Load each channel to 2 ohms. Inject a 1 kHz sine
wave and measure at least 28.64 VAC. All power
measurements must be at less than 0.1% THD.
Test 13: Reactive Loads
Spec:
No oscillations. Safe with all types of loads.
Initial Conditions:
Controls per standard.
Procedure Capacitive:
Load each channel to 8 ohms in
parallel with 2 µF. Inject a 20 kHz sine wave with 33
VAC output for 10 seconds.
Procedure Inductive:
Load each channel to 8 ohms in
parallel with 159 µHenries. Inject a 1 kHz sine wave
with 15 VAC output for 10 seconds.
Test 6: Voltage Gain
Spec 26dB Gain:
Gain of 20.0 ±3%.
Spec 0.775V Sensitivity:
±6%.
Spec 1.4V Sensitivity:
+12%/–6%.
Initial Conditions:
Controls per standard.
Procedure:
No load connected. Inject a 0.775 VAC 1
kHz sine wave with the Sensitivity Switch in the 26 dB
position. Measure 15.5 VAC ±0.5 VAC at the amplifier
output. Inject a 0.775 VAC 1 kHz sine wave with the
Sensitivity Switch in the 0.775V position. Measure 43.4
VAC ±2.6 VAC at the amplifier output. Inject a 1.4 VAC
1 kHz sine wave with the Sensitivity Switch in the 1.4V
position. Measure 43.4 VAC +5.2/–5.6 VAC at the
amplifier output. Return the Sensitivity Switch to the 26
dB position.
Test 7: Phase Response
Spec:
±10° from 10 Hz to 20 kHz at 1 Watt.
Initial Conditions:
Controls per standard, 8 ohm load on
each channel.
Procedure:
Inject a 1 kHz sine wave and adjust for 1
Watt output (2.8 VAC). Check input and output signals
against each other, input and output signals must be
within 10° of each other.
Test 8: Level Controls
Spec:
Level controlled by level controls.
Initial Conditions:
Controls per standard.
Procedure:
No Load. Inject a 1 kHz sine wave. With
level controls fully clockwise you should see full gain.
As controls are rotated counterclockwise, observe
similar gain reduction in each channel. When com-
plete, return level controls to fully clockwise position.
Test 9: Current Limit
Spec:
Current Limit at 20 Amps, ±2 Amps
Initial Conditions:
Controls per standard.
Procedure:
Load each channel to 1 Ohm. Inject a 1 kHz
differentiated (or 10% duty cycle) square wave. See
figure 4. Increase output level until current limit oc-
curs. Current limit should occur at 20 ±2 Amps (20
Vpk). Observe clean (no oscillations) current clipping.
In
Out
.047 uF
1K Ohm
Figure 4. Differentiator Circuit
