Shure FP33 manual User Adjustments, Internal Modifiable Functions

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CONNECTING FP33 TRANSFORMER BALANCED OUTPUTS TO TELEPHONE LINES

In the Line position, the Left and Right XLR outputs can be used to drive dc-biased, “dialed up” telephone lines, although there may be a slight increase in distortion. Use of the limiter circuit is strongly advised, with the FP33 limiter threshold set to +4 dBm. Modification of the FP33 output im- pedance to 600: is recommended for proper fidelity. (See the Internal Modifiable Functions section for instructions.) When connecting the FP33 to a telephone line in the United States, use of an FCC-Registered interface adapter between the mixer and the telephone line is mandatory. Outside the U.S., consult the local telecommunications authority.

USER ADJUSTMENTS

VU Meter Adjustment

To set the VU Meters to a value other than the factory setting (0 VU = +4 dBm), proceed as follows:

1.Connect a 600 : load across the Left XLR output set for Line.

2.Connect an ac voltmeter (such as the HP 400GL) in parallel with the load.

3.Slide the 1 kHz tone oscillator switch to the On (up) position.

4.Adjust the 1 kHz Tone Oscillator level with the Left (inside) Master gain control until the ac voltmeter read- ing is at the level desired.

5.Open the battery compartment door and adjust the Left VU Level trim pot with a screwdriver until the Left VU Meter reads 0.

6.Repeat the above procedure for the Right Output and the Right VU Meter.

Limiter Threshold Adjustment

To adjust the Limiter threshold to a value other than the factory setting (+15 dBm), proceed as follows:

1.Connect a 600 : load and an ac voltmeter across the Left Line output as described in steps 1 and 2 of the VU Meter Adjustment procedure.

2.Open the battery compartment and move DIP switch 1 to the Off position (refer to the chart on the inside of the door).

3.Slide the 1 kHz tone oscillator switch to the On (up) position.

4.Slide the Limiter switch to the Off (down) position.

5.Adjust the Left Master gain control until the ac voltme- ter reading is 2 dB above the desired output level.

6.Slide the Limiter switch to the On (LIM) position.

7.Open the battery compartment and adjust the Lim Adj L trim pot until the level drops to the desired reading.

8.Repeat the above procedure for the Right output, us- ing the Lim Adj R trim pot.

Peak LED Adjustment

To adjust the Peak LED threshold to a value other than the factory setting (+17 dBm), proceed as follows:

1.Connect a 600 : load and an ac voltmeter across the Left Line output as described in steps 1 and 2 of the VU Meter Adjustment procedure.

2.Slide the 1 kHz tone oscillator switch to the On (up) position.

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3.Slide the Limiter switch to the Off (down) position.

4.Adjust the Left Master gain control until the ac voltme- ter reading is at the desired peak output level.

5.Open the battery compartment and turn the Peak LED L trim pot completely clockwise.

6.Slowly adjust the trim pot counterclockwise until the left Peak/Lim LED first illuminates red.

7.Repeat the above procedure for the right Peak/Lim LED, using the Peak LED R trim pot.

Headphone Level Adjustments

To adjust the program level to match the audio signal levels from a monitored source, proceed as follows:

1.Open the battery compartment and adjust the Head- phone Level L and Headphone Level R ful counterclock- wise.

2.Connect the device to be monitored via the 3.5 mm Monitor In jack.

3.Move the Monitor Input Switch on the front panel to the locking position (left).

4.Adjust the monitor input level, using the headphone gain control on the front panel.

5.Move the Monitor Input switch on the front panel to the post-master audio position (center).

6.Adjust the post-master audio to a comparable level, using the Headphone Level L and Headphone Level R potentiometers.

INTERNAL MODIFIABLE FUNCTIONS

Selected internal functions of the FP33 can be modified by the user to fit special applications. Procedures for per- forming these modifications are listed below.

CAUTION: Due to the complex construction and exten- sive use of surface-mount components, modifications to the FP33 must be performed by a qualified service techni- cian. Contact the Shure Service Department or your au- thorized Shure Service Center for further information on these modifications.

Disassembly

1.Remove the six screws that secure the cover.

2.Slowly slide the cover backwards and unplug ribbon cable P109.

3.Remove the three screws (marked with arrows) that secure the upper PC board.

4.Remove the upper PC board.

5.Perform the appropriate modification procedure.

6.Reassemble the unit by doing Steps 1–4 in reverse.

Changing the Line Level Output Impedance to 600 :

1.Locate R674 and R668 on the bottom PC board and remove them.

2.Locate X503 and X505 on the bottom PC board and sol- der a 470 : 1/2W resistor through the holes at X503.

3.Solder a 470 : 1/2W resistor through the holes at X505.

Changing the Tape Out Jack from Stereo (tip = L; ring = R) to Mono (tip = L+R; ring = L+R)

1.Locate X504 on the top side of the lower PC board, by the Tape Out jack.

2.Solder a jumper through the holes at X504.

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