d. Adjust the Low Battery Cut-off Circuit. Refer to Appendix G, Porta Pak 90
Defibrillator Schematic, section B-10.
(1) With the power supply connected to J4 as for the battery meter (see
paragraph f(3)), close the power switch and observe it light up.
(2) Adjust R113 to a point where the light just turns off at 9.5v. This is the
proper setting for the low battery cut-off.
e. Adjust the Battery Charger (NiCad). Refer to Appendix G, Porta Pak 90
Defibrillator Schematic, section B-10.
(1) Disconnect the battery from the charging circuit and substitute a resistive
load of 75 ohms ( 5 percent). This load should have a power rating of approximately 5w.
(2)
Plug the unit into an outlet. The rest of the unit should remain turned off.
(3) Adjust RA2 until an ma meter in series with the 75 ohm load reads 250ma.
Short circuit the load for a few seconds at a time. The current should not increase by more
than 70ma, showing correct action of the current regulator circuit.
(4) Turn on the unit. With nominal line voltage (120v or 230v RMS), the
charge current through the load should not fall by more than 60ma. The voltage across the
load resistor should be at least 14vdc with the unit turned off. A discharged NiCad battery
in good condition should recover 100 percent of its charge in 14 hours at room temperature
(approximately 70 degrees Fahrenheit).
f. Calibrate the Delivered Energy. Refer to Appendix G, Porta Pak 90
Defibrillator Schematic, section C-4.
CAUTION:
The power supplies and ground of this entire pcb may be as much as
1360vdc above ground potential of the rest of the unit.
(1) Turn on the power switch; however, do not charge the defibrillator. Any
calibration has to start with the reference voltage of the digital voltmeter. The voltage has
to be exactly 1.000vdc between test points 1 and 2, connecting pin 37 of U38 to +5v of the
on board supply. All segments of the three display digits should light up. Do not leave the
system in this condition for more than 10 seconds.
(2) Turn off the power switch. Wait a couple of seconds and turn it on again.
The display should light up showing 000,001 is acceptable. If any significant reading
appears, turn R160 (zero balance) until 000 is displayed each time the unit is turned on.
NOTE:
For the following steps, a defibrillator tester is needed with a standard load of
50.0 ohm.
MD0362
1-23
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