Orban OPTIMOD-FM 8600, Operating Manual

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4-8
MAINTENANCE ORBAN MODEL 8600
It is assumed that the technician is thoroughly familiar with the operation of this
equipment.
This procedure is useful for detecting and diagnosing problems with the 8600's per-
formance. It includes checks of frequency response, noise and distortion perfor-
mance, and output level capability.
This performance audit assesses the performance of the analog-to-digital and digi-
tal-to-analog converters and verifies that the digital signal processing section (DSP)
is passing signal correctly. Ordinarily, there is a high probability that the DSP is per-
forming the dynamic signal processing correctly. There is therefore no need to
measure such things as attack and release times—these are defined by software and
will automatically be correct if the DSP is otherwise operating normally.
It is often more convenient to make measurements on the bench away from high RF
fields which could affect results. In a high RF field it is, for example, very difficult to
accurately measure the very low THD produced by a properly operating 8600 at
most frequencies. However, in an emergency situation (and is there any other kind?),
it is usually possible to detect many of the more severe faults that could develop in
the 8600 circuitry even in high-RF environments.
See the assembly drawings in Section 6 for component locations. Be sure to turn the
power off before removing or installing circuit boards.
Follow these instructions in order without skipping steps.
Note: To obtain an unbalanced output, jumper pin 1 (ground) to pin 3 and measure
between pin 1 (ground) and pin 2 (hot).
Note:
All analog output measurements are taken with a 620
Ω
±5% resistor tied be-
tween pin 2 and 3 of the XLR connector.
1. Prepare the unit.
A) Set the
GND LIFT
switch to the earth ground symbol setting (left position) to
connect chassis ground to circuit ground.
B) Use the front panel controls to set the 8600's software controls to their de-
fault settings, as follows:
a) From the main menu, choose Input/output. Using the Locate joystick, navi-
gate in turn to each of four Input/output screens and write down the set-
tings so you can restore them after testing.
b) Navigate to the
I
NPUT
/O
UTPUT
> I
NPUT
screen. Set controls as in the table be-
low:
Set Input to .................................................................................. analog
Analog Ref. Level ...................................................................... +4.0 dBu
Clip Level ................................................................................. +20.0 dBu
Right Channel Balance .................................................................. 0.0 dB
DI REF VU ............................................................................... –15.0 dBFS