Microplane 201 - Manual (Page 7)

screws that hold each rack ear in place. After removing the rack ears replace the
two lower screws on each side of the preamplifier.
III. MAINTENANCE
A. The model 201 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 the Grace Design factory.
B. 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 red threshold
follows.
1. EQUIPMENT NEEDED
i. Sine wave audio signal generator or oscillator output from a mixing console.
ii. Audio level meter or VTVM
iii. Plastic alignment tool or small screwdriver
iv. Appropriate interconnect cables
v. #2 Phillips screwdriver
2. PROCEDURE
i. With the power off, remove the top cover from the 801. Set all of the gain
controls to the 9 O'clock position. (30dB gain)
ii. Connect the audio generator to the input of channel 1. Set the output level to
approximately -20dBu @1KHz. If the generator has an unbalanced output
refer to Figure 6 below for termination information.
3
1
2 SHIELD
HOT
XLR MALE
Figure 6. UNBALANCED INPUT CABLE
iii. Connect the level meter to the output of channel 1. Set the input attenuator to
+20dbu range. If the generator has an unbalanced input refer to Figure 1 for
termination information.
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