APX 525/625 Generator Revision C Service Adjustments
©
2005 Del Medical Imaging Corporation
7/5/2005 Page 158
5. If the measured density is not 1.2 (+/- .05), divide 1.2 by the density measured on
the film and multiply the quotient by the mAs of that exposure. This number is the
first approximation of the required exposure mAs for 72 kV to obtain a density of
1.2. Record this mAs
Sample Calculation
kV setting = 72
Exposure mAs = 30
(1.2 / 1.63) x 30 = 22
mAs
6. Locate R130 (R129 if calibrating screen 2) on the Gain Adjust PWB (124-0125).
Using the same film cassette without film, take an exposure
7. Compare the mAs of the current exposure (30 in the sample above) with the mAs
calculated (22 in the sample above) to obtain a 1.20 density. If the current
exposure mAs is smaller, turn the pot counter-clockwise. Take exposures until
the mAs of that current exposure as indicated on the generator control is close to
the calculated mAs. If R130 or R129 cannot be set low enough, then the gain
setting of the preamplifier of the ion chamber is set too high. Consult the
manufacturer for chamber gain adjust information
8. Take another film and measure the density. If the measured density is not 1.2 +/-
.05 return to step 4 and repeat steps 4 through 8
9. The master screen gain for Screen 1 (R130) has now been calibrated. It must not
be changed for the remainder of the calibration procedure
10. Repeat steps 4 through 8 for 40, 56, 90, and 125 kV. For each kV, use the
settings listed below. Be aware that pots for individual kV gain work opposite
than the pot described in step 7. If the current mAs is larger, turn the pot
counter-clockwise to decrease
kV Generator
mAs
Inches of Water
(Plastic)
Pot to
Adjust
40 100 1 (2.54 cm) R133
56 70 4 (10.16 cm) R135
90 70 8 (20.32 cm) R139
Screen 1- 200 speed
system
125 70 10 (25.4 cm) R141
40 70 1 (2.54 cm) R134
56 70 5 (12.7 cm) R136
90 70 9 (22.86 cm) R140
Screen 2- 400 speed
system
125 70 10 (25.4 cm) R142
Screen 2 (400 speed) is calibrated in a similar manner using the appropriate controls
and pots for screen 2. Start with Step 1.
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