Service manual

Troubleshooting
Revised 2/18/05 6-21
Filter Tests
The Endeavor CR and Viking amplifier systems use a
combination of digital (software) and hardware filters.
Normally, the USB/FireWire diagnostics will detect
amplifier problems. If, however, you experience a wave
shape-related problem that is ambiguous in nature, you
may want to verify that all hardware filters are working
properly.
The generic test for hardware filters is to run a common
square wave calibration pulse through all amplifier
channels, and observe the effects of the filter settings on
the shape of the waveform. This test works best with all
channels displayed at the same time and, if possible,
overlaid. A time base of 10ms full screen (1ms/div) is
optimal for showing changes in wave shape. On the
Viking, an EP or MMP test screen can be set up for
performing the filter tests. The VikingQuest requires an
external calibration pulse.
NOTE: Version 7.4 VikingQuest software does not
allow checking filters by this method, as the
amplifier is shut off during presentation of
the external cal pulse for purposes of
stimulus artifact reduction. Software version
8.2 will feature a Calibration mode, where
the artifact reduction feature will be turned
off.
Low Frequency Filter
Start with the LFF and HFF filter settings wide open. As
you raise the LFF setting, the waveform shape gradually
changes to a form that resembles the charge/discharge
current in a capacitive circuit
.
High Frequency Filter
Start with the LFF and HFF filter settings wide open. As
you lower the HFF setting, the waveform shape
gradually rounds off.
The example below shows a VikingSelect EP waveform
screen set up to perform a filter check on eight overlaid
amplifier channels.
LFF=0.5Hz
HFF=15kHz
LFF=10Hz
HFF=15kHz
LFF=100Hz
HFF=15kHz
Effects of LFF Settings on a
Square Wave Calibration Pulse
LFF=0.5Hz
HFF=15kHz
LFF=0.5Hz
Hff=5kHz
LFF-0.5Hz
HFF=1kHz
Effects of HFF Settings on a
Square Wave Calibration Pulse