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Appendix
4. Switch BLK in and re-adjust HMF Frequency for maximum level.
5. Adjust VR16 for +18dBu ±0.25dB.
6. Reset HMF Gain to its centre indent position and release the BLK switch. Re-
check the audio level meter for 0dBu.
HF EQ – Maximum Gain
Adjustment: 1. Ensure that the BLK switch is released.
2. Set HF Gain to maximum and select HF BELL. Set the audio oscillator for 12kHz
and adjust HF Frequency to find the maximum level on the audio level meter.
3. Adjust VR19 for +15dBu ±0.25dB.
4. Switch BLK in and re-adjust HF Frequency for maximum level.
5. Adjust VR21 for +18dBu ±0.25dB.
6. Reset HF Gain to its centre indent position, de-select HF BELL and release the
BLK switch. Re-check the audio level meter for 0dBu.
Dynamics Adjustments
If the dynamics circuitry requires adjustment the following procedure should be followed in the order shown, in
its entirety. All presets are on the 629612 card.
Equipment Required: Calibrated audio oscillator, audio level meter and a (digital) dc. volt meter
Test Signal: 1kHz sinewave unless specified otherwise, level as specified
Input and Output: Oscillator to Line Input, Output to the audio level meter.
Unit Setup: Switch the dynamics IN and the EQ and Filter sections OUT, set all of the
dynamics controls anti-clockwise and release all switches
Unity Gain
Adjustment: 1. Set the oscillator for 0dBu.
2. Adjust VR26 for 0dBu ±0.05dB.
RMS-to-DC Converter Gain
Adjustment: 1. Set the oscillator for –3.2dBu.
2. Measure on TP30 and adjust VR27 for –1.7V ±50mV.
RMS-to-DC Converter DC Offset
Adjustment: 1. Set the oscillator for 0dBu.
2. Measure on TP22 and adjust VR25 for –3.0V ±50mV.
Gate Threshold
Adjustment: 1. Set the oscillator for +14dBu.
2. Adjust VR25 until the gate just opens.
3. Check this adjustment by changing the oscillator level a little. Re-adjust VR25 if
necessary so that the gate just opens when a +14dBu signal @ 1kHz is applied.