Grace M201 owner manual Maintenance, Peak LED Adjustment Procedure, Equipment Needed

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Maintenance

The model m201 was designed to be maintenance free for many years. It is highly unlikely that your unit will require service. However, there are two adjustments that may need to be made from time to time. These procedures should be made only by a qualified service technician or at the Grace Design factory.

PEAK LED ADJUSTMENT PROCEDURE

The peak LED threshold levels may be adjusted to a user defined operating level. This circuit is set at the factory with the green threshold at -14dBu and the red threshold at +16dBu. The relationship between the two thresholds is fixed. The procedure for adjusting the greed / red threshold follows:

EQUIPMENT NEEDED

•Sine wave audio signal generator or oscillator output from a mixing console.

•Audio level meter or an RMS Volt meter with dBu or dBm scales

•Plastic alignment tool or small screwdriver

•Appropriate interconnect cables

•#2 phillips head screwdriver

PROCEDURE

1) With the power off, remove the eight phillips head screws from the top cover and remove it from the m201

2) Set all of the gain controls to the 30dB position

3) Connect the audio generator to the input of channel 1

4) Set the generator output level to approximately -20dBu @1KHz.

5) If the generator has an unbalanced output, refer to figure 2 below for termination information

6) Connect the level meter to the output of channel 1.

7) If the level meter has an unbalanced input, refer to <figure 1> output termination information.

8) Apply power to the generator, preamplifier, then the level meter.

9) Adjust the generator output level so that the preamplifier output level is at the desired red threshold. If the proper level can’t be reached, adjust the preamplifier gain control.

10) Locate VR2A (VR2B for channel 2) (see <figure 3>) on the channel 1 audio circuit board and adjust until the peak LED is between green and red. The color should appear amber when the setting is correct. Repeat this procedure for channel 2.

11) If it is desired to calibrate the peak indicator to a specific converter/recorder input level, simply connect the output of the preamplifer to the converter/re- corder. Adjust the signal generator so that the desired peak level is indicated on the recorder and then adjust VR1 until the peak LED is between green and red.

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grace design m201 owner’s manual