Watchdog Timer Troubleshooting; Accessing Watchdog Timer Diagnostics (Dia 1); Dia 1 Mode Selection; Troubleshooting With Diagnostics 1 - ConMed Sabre 2400 Operators & Service Manual

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In Diagnostics 2, the unit operates exactly as
in normal RUN mode and will deliver RF to
the output jacks, except the following software
routines which detect hardware faults are not
executed:
• Microprocessor internal RAM validity
• Calibration EEPROM CRC validity
• Power Amp Overcurrent Protection
• ARM Circuit failure detection
• Hand, Foot or Keyboard activation on
Power-Up.
The routine that checks for the Program EPROM
CRC validity will still be active.
CAUTION: If any of those failures exist, the
microprocessor will not shut the system down
or display a HLP code. One should be pru-
dent in deciding whether or not to enter this
mode without first attempting to identify the
fault while powered down.
As an example of the above note, if there is a
problem with the Power Amplifier which causes it
to draw excessive current, say a shorted FET, then
activating the unit can allow the fault current to
flow for the duration of the activation. This may
result in damage to other components which had
previously been spared by the microprocessor's
fast response to overcurrents in RUN mode. The
time saved by not first performing an ohmmeter
test of the FET will be lost in identifying and
replacing parts damaged by the undetected over-
current.

4.7.3 Watchdog Timer Troubleshooting

This section contains help in troubleshooting the
Watchdog Timer on the Controller PWB A2.
A faulty Watchdog Timer (WDT) will cause the
microprocessor to stop generating the WDSTR
signal in RUN mode. Troubleshooting this circuit
is difficult without that signal, and setting up an
external generator and connecting it to the circuit
is time-consuming.
4-16
4.7.3.1 Accessing Watchdog Timer
Diagnostics (dIA 1)
To enter diagnostics 1, enter the CAL MODE per
section 4.6.1 then select "dIA" in the Cut window
by pressing the Cut Power I in Decrease Key.
The menu will display dIA 1. Press the "SEL " key
again.
Since this mode is useful only with the /RLYEN
flag in the reset state, "dIA" will not appear in
the menu once RF has been activated in any of
the power calibration modes. On the other hand,
if a faulty WDT is detected on initial entry to
CAL MODE, Diagnostics 1 will be automatically
entered, bypassing the menu, since proper calibra-
tion may be impossible if the WDT is faulty.
The menu cannot be restored from this mode.
When work is complete, exit CAL Mode by pow-
ering down. This mode has no effect on the
EEPROM, so the calibration and CRC are
unchanged.

4.7.3.2 dIA 1 Mode Selection

An indication of the currently selected mode
appears in the Bipolar Power window. Modes are
selected round robin fashion by using the Coag
(righthand) foot switch to step up to the next
higher mode, and the Cut treadle to step down.
Table 4.8 lists the available modes.
If the WDT is operating normally the Return
Monitor Lamp will appear as shown in Table 4.8
until Lockup Mode 4 is selected and then either
Late Mode 2 or Early Mode 3 is selected. After
that, the Return Monitor Lamp should be bright
in all modes. This indicates that the WDT has
effectively locked up, as it should.

4.7.3.3 Troubleshooting with Diagnostics 1

Since the WDT timing accuracy and ability to
interrupt RF output are verified by the micro-
processor on every power up, there is no need to
recheck these parameters periodically. The only