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CALIBRATION PROCEDURE FOR THE BBE® MODEL 702
THE MODEL 702 WAS CALIBRATED AT THE FACTORY SO CALIBRATION IS
NOT NECESSARY. THIS PROCEDURE IS FOR SERVICE PERSONNEL ONLY
Date: April 17,1990 - Revision H
EQUIPMENT REQUIRED:
1) Audio Signal Generator (sine wave)
2) Two digital voltmeters (DVM #1 and DVM #2)
INITIAL SETTINGS:
1) DEFINITION control to minimum (just prior to bypass).
2) LO-CONTOUR control and all internal potentiometers to their middle positions.
3) IN:AUTO button to the "in" position.
•Since both channels are identical in calibration and component numbers only
channel A will be outlined. (Channel B will be in brackets).
•All tests are done with a signal level of OdBu (0.775Vrms) except for the clip
test.
•The signal will be input into the corresponding channel connector marked "A"
for channel 1, "C" for channel 2.
•The DVM #1 will monitor the output of the corresponding channel marked "B"
for channel 1, "D" for channel 2.
•The DVM #2 will be used to measure various test points in the test
procedure (relative to ground).
PROCEDURE:
Offset Adjustment:
1) With no signal present at the input (open), measure TPA [TPB] with the DVM
#2 set to DC volts.
2) Adjust VR5A [VR5B] until DVM reads O.OOVdc.
Power Supply Test:
1) With DVM set to DC volts measure pin 4 of U1. It should be -15VDC
(+/- .5VDC).
2) With DVM set to DC volts measure pin 8 of U1. It should be + 15VDC
(+/- .5VDC).
3) With DVM set to DC volts measure the cathode of D7. It should read 24VDC
(+/- 2.0VDC).
Unity Adjustment:
1) Input a signal of 5000Hz (OdBu) into the input and adjust VR3A [VR3B] for a
reading of -4.00dBu as read by DVM #1.
2) Input a signal of 500Hz (OdBu) into the input and adjust VR6A [VR6B] until
DVM#1 reads-I.OOdBu.
3) Repeat steps 1 thru 2 as some interaction exists.
Lo~Contour Test:
1) Input a signal of 50Hz (OdBu) into the input and adjust the LO CONTOUR
control to the middle position marked "0". DVM #1 should read +3.00dBu
(t.lVrms) (tolerance= +/- t.OdBu).
2) Turn the LO-CONTOUR to
(minimum). You should read -lOdBu
(0.245Vrms) on DVM #1 (+/- I.OdBu).
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