Quad 303 all versions illustrated upgrade guidelines V2.0
Page
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Step 5
– Calibrating the voltages and the quiescent-current
Beware: to get meaningful results, please perform the calibration without any
signal source or loudspeaker connected to the 303 concerned!
•
Connect a DC multimeter between pins (wire) 1 and 9 on one of the driver
boards. Adapt RV200 on the PSU-board until you measure exactly 67 Volt DC.
•
Connect a DC multimeter between pins 1 and 5 on a driver board. Adapt
RV100 until exactly (!) 33.5 Volt DC is measured. Repeat this step for the
other driver board.
•
Connect a multimeter between pins 4 and 6 on any of the driver boards. Set
the multimeter to its DC millivolt (mV)-range.
•
Adapt RV101 until you measure at least 6 mV DC. A somewhat higher value
will not pose a problem, but 15mV is about the maximum. The optimum is 10
"
WARNING
!
Be sure to remove the boards completely from the plastic clips
during the calibration, the same goes for the backend. Contact between the
track (copper) side of the printed circuit board and the chassis should be
avoided at all time. Non-compliance will result in destroying the driver
boards and the power transistors." Please refer to the graphic hereunder;
use for instance a small piece of wood bar to meticulously isolate the Pcb
from the chassis.
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