Microplane 201 owner manual Iii.Maintenance

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.

2

XLR MALE

3

HOT

1SHIELD

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.

Page 6