ConMed ExcaliburPLUS PC - Component Level Troubleshooting

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11 msec after each WDTSTB, and Stage 2 should
run from 13.5 to 16.5 mS. WDTSTB is a very
short pulse and may be difficult to see with an
oscilloscope. Slight timing errors are most likely
due to a faulty timing resistor or capacitor.
Failure of the pulses to respond at all are more
indicative of an IC failure.
An Err 7.0 indicates that the WDT did not shut
down RF when Stage 2 timed out. This may be
caused by failure of any of the components carry-
ing
the WDTEL signal to the WFG and VBASE
circuits.
4.7.4 Base Voltage Generator Troubleshooting
Remove all base fuses on the A4 Power
Conversion Assembly before checking a suspect
Base Voltage Generator (BVG). Enter the dIA 2
mode (see section 4.7.2). Check that A3U20 is
producing the proper VDAC voltage at A3TP14.
Do this by selecting the Monopolar Blend 1 Cut
mode, and increasing the power setting from 0 to
180W. Monitor TP14 to see that VDAC goes
from approximately 9.95 Vdc at 0W to 2.5 Vdc
at 180W when activated. The VDAC voltage at
180W will vary from unit to unit, the important
factor is that the voltage changes in small incre-
ments.
Next monitor A3TP12 and repeat the above pro-
cedure. Confirm that TP12 voltage increases
from no more than 0.4V at OW to approximately
4.5 Vdc at 180W. If it fails to do so, check that
VSENSE and ISENS are both less than 0.6V
(this is true only if the base fuses have been
removed).
Other problem sources could be one of the resis-
tor divider chains in the BVG, a bad RFEN or
WDTEL signal. Also check that the other compo-
nents in the BVG chain are correct and function-
al.
If the BVG performs correctly as tested so far,
and the Power Amplifier and Waveform
Generator both test good, proceed with the fol-
lowing test. Turn off the unit and replace the
fuses in the PA. Reenter dIA 2 and select
Monopolar Blend. Monitor A3TP13 (VSENSE)
and slowly increase the power setting on the
front panel. When functioning correctly, TP13
4-20 (=
will increase with power setting up to about 5.6
Vdc. At that point, there should only be a slight
increase in TP13 voltage. If TP13 fails to
increase towards 5.6 Vdc, do not proceed with
this test; find the failed components and repair
them.
After successful testing of the VSENSE circuit,
connect a 300 ohm 250W load resistor to the
unit’s RF outputs. Select Monopolar Pure Cut
and slowly increase the power setting while mon-
itoring A3TP15. The de voltage at TP15 should
increase as power increases, but should not exceed
5.4 volts at full power.
Units that have passed the troubleshooting steps
so far should be checked for properly oriented
diodes, mismarked resistors, and correct divider
voltages. If the unit has passed these BVG checks,
then the problem is likely elsewhere.
4.7.5 Waveform Generator Troubleshooting
Enter the dIA 2 mode (see section 4.7.2). Check
that a 20.0 MHz clock appears at A3TP32. Select
a power setting and mode that corresponds to the
photos in Fig. 3.5 and confirm the waveforms are
similar to that at A4TP4 when activated (use
A3TP20 to trigger the oscilloscope to get compa-
rable results). If they are not, suspect one of
A3U13-U18 as being bad. Another problem
could be in the waveform select lines WVO-WV7.
4.7.6 Aspen Return Monitor (A.R.M.)
Troubleshooting
The overall functionality of the A.R.M. circuitry
may be checked per Section 4.5.7.
If these tests pass, but the unit still declares unac-
countable Return Fault in operation with the
ESU activated, interference from electrosurgical
current is the likely cause. Check the A5T5 shield
lid for good electrical and mechanical contact
with the shield cup, and capacitors A5C44 and
C45 for proper value and connection. Also check
bypass
capacitors ASC15, A3C25 and low pass
filter capacitor ASC38.
If the ASSIST Resistance Indicator vs. resistance
test fails, check BVARM at A3TP16 with 10 and
150 ohms connected to the Return Electrode