6.3.6
Generator PCB,
continued
Chapter 6 - Detailed Diagnostics
continued
All the tests below are made in reference to circuit ground, which is found at TP4, TP10, and TP15. This common
circuit ground is NOT earth ground, and is not intended to be connected to earth ground. It is therefore important to
break the earth ground connection to the generator before connecting any test equipment to circuit ground.
1.
Verify the processor controlled switching DC supply is regulating properly:
•
With power removed from the generator, clip the leads of the DVM (set for VDC) to TP6, and common
ground (TP4, TP10, or TP15). Apply power, switch the generator on, and verify that TP6 is between 15
and 25 VDC.
WARNING: Higher voltages indicate improper supply regulations; remove power quickly if the voltage
exceeds 100 VDC. Even after power is removed, hazardous charge may be retained on the power supply
capacitors. If continued testing is desired, disable this supply by removing the fuse(s) to the high voltage
transformer.
•
With power removed from the generator, clip the oscilloscope (set for a 5 volt pulse at 60 to 50 Hz) to
TP16. Apply power, switch the generator on, and verify that a positive fixed width pulse approximately
1 msec wide and synchronized to the line frequency exists.
•
If higher or lower voltages are noticed, either this portion of the generator PCB is bad or the
microprocessor PCB is unable to regulate the DC voltage. If this is the case, re-test the generator PCB
with a substitute microprocessor PCB before replacing this PCB. If the pulse at TP16 is not synchronous
with the line rate, replace the generator PCB.
2.
Verify that the low voltage DC supplies are regulating properly:
•
With power removed from the generator, clip the common lead of the DVM (set for VDC) to common
circuit ground. Sequentially, clip the other lead to each of the test points listed below, turn the generator
power on, and verify the appropriate voltages:
TP1:
+5 VDC +/- 20 mV
TP2:
+12.65 VDC +/- 250 mV
NOTE: TP2 may be slightly difficult to access. Even with the microprocessor PCB in the service
position, TP2 is still located under the microprocessor PCB.
•
If higher or lower voltages are noticed and the output of the low voltage transformer has been verified
(see section 6.3.4), replace the generator PCB.
3.
Verify that the ultrasonic drive circuit is functioning properly:
Caution: During this testing the instrument blade will become active. Do not touch the blade.
•
With the power removed from the Generator, clip the oscilloscope (set for 2 volts at 55,000 Hz) to TP11.
Apply power, switch the generator on, and energize the hand piece at full power for several seconds.
•
The voltage wave form at TP10 should be between 1V to 1.22 peak to peak at a frequency between
54,000 Hz to 55,500 Hz and approximately sinusoidal. This spread in voltage and frequency is caused by
variations in the type of blade attached to the hand piece and the hand piece itself. Therefore, if the
voltage or frequency is not within range, re-test with a different hand piece and blade before replacing
the generator PCB.
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