uniphy Phyaction 740 Series, Service Information

Page: 29 / 68

Service Information Phyaction 740 & 790-series Page 27
5 .2 Error shutdown procedure
The safety circuit will switch off the safety relay directly in the event of an error, thus disconnecting the
output from the unit to external connections to avoid danger to the patient.
In addition to this the microprocessor will, if it detects an error either from the safety circuit or otherwise,
perform the following actions:
-
Safety relay off: Patient circuit disconnected. This is a latched condition that can only be
reversed by switching off the unit.
- Dummy relay off: The output is short circuited. (This can only occur if the current dosage
regulator is at zero).
- Choppers off: No signal to the output stage (no output current).
- MF-Dac's to zero: No signal to the choppers
- US-Dac to zero: The power supply of the ultrasound output stage is set to minimum.
- US duty cycle off: The ultrasound modulator will be switched off.
- PB-enable off: The laser probe is switched off.
- Laser drip charger off: The laser power supply is switched off.
- Red error-LED on
- Fan on
- An error message is displayed on the LCD screen. In some cases the yellow monitor-LED is
pulsed in case the processor has not established communications with the LCD screen yet.
5
.3 General test description
The microprocessor gathers its information via digital and analog inputs and these are tested first. Next
the current generator and its safety circuits are tested, then the ultrasound generator and the laser
generator. Finally some additional simple tests are performed.
In case the unit does not finish the selftest, no error message is displayed, the buzzer is not pulsed and
all internal wiring is connected properly the following items are suspect :
-
Supplies (mains and other)
- Microcontroller
- Program
EPROM
- Address, data or control lines
5.3.1 Microcontroller core test
Any errors found will stop the selftest and an error message will be displayed.
MICROCONTROLLER TEST
The following tests are performed:
1
MF-Error line check. If the MF-error line is in error condition (safety relay switched off) the buzzer
will be activated 7 times (
ERROR 57 ).
2 The microcontroller arithmetic and logic unit (ALU) check. The controller executes a number of
arithmetic operations and compares the calculated value with the correct value. In case of failure
the buzzer will be activated 4 times (
ERROR 20, error code 0 ).
3 Test of the internal RAM. The controller writes some data to the internal RAM and compares the
data read from the RAM with the original data. In case of failure the buzzer will be activated 4
times (
ERROR 20, error code 1 ).
4 Test of the external RAM. The RAM is tested for writeabilty and data retention. This also checks
address, data and read/write control lines. Incase of a failure the buzzer will be activated 5 times
(
ERROR 22 ).