Lf Protection; Signal To Noise; Intermodulation Distortion (Imd); Displays - Crown Com-Tech CT-1610 Service Manual

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6.2.16 LF Protection

Spec: Amplifier channel will cycle into protect with .5
Hz 6Vp-p or 2 Hz 6 Vrms sine wave at the output.
Procedure: Inject a 2 Hz sine wave into the input of
the channel under test. Increase the level until the
amplifier cycles on and off. It should cycle on and off
when the output reaches approximately 6 Vrms.

6.2.17 Signal to Noise

Spec CT-810 : 100 dB below 295 watts into 8 ohms.
20Hz-20kHz unweighted.
Spec CT-1610 : 100 dB below 520 watts into 8 ohms.
20Hz-20kHz unweighted.
Procedure: Short inputs. Load each channel to 8 ohms.
On a CT-810 , measure less than 486µVrms at the out-
put of each channel. For the CT-1610 , the measure-
ment should be less than 645µVrms.

6.2.18 Intermodulation Distortion (IMD)

Spec: 8 ohms, 0dB = FTC continuous average 20Hz-
20kHz power
0 dB < .01%
-35 dB < .05%
Procedure: Load each channel to 8 ohms. Inject a
SMPTE standard IM signal (60 Hz and 7 kHz sine wave
mixed at 4:1 ratio). Set the 60 Hz portion of the signal
for 23 Vrms output. Set the 7 kHz portion to 25%. With
the IM analyzer measure less than 0.01% IMD. Repeat
the test at -35 dB and measure less than 0.05% IMD.
6-4
Com-Tech 810 and 1610 Amplifier Service Manual

6.2.19 Displays

Spec:
Enable - On when low voltage supply is on.
ODEP - Dims in proportion to ODEP limiting.
IOC - On with error amp clip (distortion).
SPI - Flash in sync with amplifier output.
Procedure: Verify indicators per above specifications.

6.2.20 Auto Standby Operation

Spec: Amp goes into standby after 30 minutes of no
input signal.
Procedure: Remove the jumpers on TP100 and TP200
pins 3 & 4. Apply 1 volt of a 1 kHz sine wave signal to
both channels. Turn off or remove the signal. After 30
seconds verify that voltage across R37 and R39 (15
ohm on output assembly) decreases to less than 20
mVrms. Any noise generated by auto standby must
be equal to or less than the residual noise of the am-
plifier. To test this use one 8 ohm speaker per channel.

6.2.21 Post Testing

After completion of testing, if all tests are satisfactory,
the amplifier controls should be returned to the posi-
tions required by the customer. If conditions are un-
known or unspecified, factory settings are as follows:
On CT810A and 1610A, remove the jumpers across pins 3
& 4 of TP100 and TP200.
Level Controls: 9 to 11 O'Clock.
Sensitivity Switch: .775V 8/4 Ohm.
Rev. 0