Specifications

5–6
FM500 User's Manual
5.5 Motherboard Adjustments
For Normal-Bypass switch setting, see section 2.10.
5.6 Display Modulation Calibration
The Modulation Calibrate trim pot sets the sensitivity of the front panel Modulation
bar graph display.
This adjustment may be made only after the Output trim pot on the Stereo
Generator board has been set. (See section 5.2.4.)
1. Set the Stereo-Mono switch to Mono.
2. Feed a sine wave source of about 2.5 kHz into the left channel at a level
sufficient to put the wideband gain-reduction indicator somewhere in the
middle of its range.
3. Set the Modulation Calibrate trim pot so that the “90” light on the front panel
Modulation display just begins to light.
5.7 Voltage Regulator Adjustments
JP701, a 10–pin header on the Voltage Regulator board, sets the time between
program failure and carrier turnoff. Pins 1 and 2 are the two pins closest to the
edge of the board. The times are approximate. Sections 2.11, 2.12, and 4.8
contain further information.
1. Short pins 1 and 2 for a 30–second delay.
2. Short pins 3 and 4 for a 2–minute delay.
3. Short pins 5 and 6 for a 4–minute delay.
4. Short pins 7 and 8 for an 8–minute delay.
You may select other times by changing the value of R721. The time is proportional
to the resistance.
5.8 Bias Set (RF Power Amplifier)
The Bias Set trim pot is located on the PA module on the input circuit board. Set
the trim pot to its midpoint for near-optimum bias.