Service manual

- alsa apparecchi medicali s.r.l. -
Pag. 4
The device consists even of other secondary sections:
a) The Double handle & neutral plate control board contains: the hand activation circuit and the neutral
plate alarm circuit, both with insulation between patient and intermediate circuits granted using
transformers (made with ferrite toroid cores with two insulated windings) capable of withstanding a test
voltage higher than 3000 VAC.
The first one works as follows:
When a push button of the hand switch (connected to the secondary winding of these transformers) is
pressed produces a variation of magnetic flow between the two windings (primary and secondary) and a
reduction of the amplitude of the signal on the primary winding. Therefore this reduction is detected by
the Microcontroller board as the activation of one of the hand switches and consequently it is enable the
H.F. power flowing through the selected output
The second one is realised according to the same principle described above and it is able to control not
only the correct connection of neutral plate (using every kind of neutral plate) but even the contact
neutral plate/tissues (only using split REM neutral plates) and works as follows:
A oscillator composed by U1A 40106)-R1-R61-C1, supplies a current at frequency of 60 kHz ±5 kHz that
drives the T1 transformer. Once the maximum amplitude of the signal is obtained using the R1 pot,
depending on the load connected to the neutral plate, a signal is sent to the window comparator
composed by U2A and U3A op ams (LM324). This comparator provides the microcontroller with the
"information" needed to distinguish the three different levels of contact between neutral plate and tissues
as described below.
Ideal contact: neutral plate/tissues resistance up to about 75 Ω (plate alarm LED off and complete use
of the device)
Poor contact: neutral plate/tissues resistance from about 80 to 150 Ω (plate alarm LED flashing and
maximum output power reduced to max 200W)
Insufficient contact: neutral plate/tissues resistance over than 150 Ω (plate alarm LED always on,
acoustic alarm on, “Err PN” on display and output power stopped).
When the unit is used with standard neutral plates (no split REM) the system works only in
situation of ideal contact (neutral plate cable not broken, well connected to the unit and to the
neutral plate) or insufficient contact (neutral plate cable broken or not connected to the unit or to
the neutral plate).
Power reader board (1) and (2): the circuits on these boards are used for two different purposes:
1) General control of all output powers
2) Dynamic optimisation and stabilisation of the output power (monopolar and bipolar), by means of a
feed back between unit and tissues (electrical load impedances), independently from the variations
of the load impedance.
3) Automatic start/stop of bipolar coagulation (function MPA) according to the variation of load
impedance (tissues).
To obtain these results the circuit supplies the microcontrollers with some signals proportional to the
output power and, according to these signals, the microcontroller “adjusts” the working parameters to
obtain the maximum possible stabilisation of the output power.
The heart of this section is a current and voltage reading transformer that picks up the signals from the
output sending them to some analog multipliers (HA325569 and AD633).
When the automatic bipolar coagulation (MPA) is selected this section evaluates also the impedance
(tissues) connected to the bipolar forceps to obtain the correct start/stop of the output power.
If the impedance is about 30 Ω, the circuit stops the automatic start to avoid a not desired activation
If the impedance is about between 30 and 850 Ω there is the automatic start.
If the impedance is higher than 850 Ω the circuit stops automatically the output power or doesn’t allow
the automatic start.
To avoid instantaneous starting as soon as the forceps touch the tissue, it is possible to adjust the
automatic starting delay (from 1 up to 6 seconds) using the rotary pot on the back of the unit.
a) Double Switch handle board: this board changes (using two relays, which are connected in series for
each monopolar output) the path of H.F. power towards the output selected and activated by the user.
On the same board other two relays are used to check the integrity of the neutral plate circuit and the
bipolar output path during the main self-test routine.
The presence of the self-test system may prevent the repair of the unit as, when a fault is pointed out, stops
the working and many signals required for the communication among the different sections are blocked.
It is therefore necessary to by-pass the self-test routine if the device has to be technically inspected.
For this purpose has been prepared an appropriate EPROM memory (Alsa code 713958) TO BE USED
ONLY AND EXCLUSIVELY DURING THE CALIBRATION PHASE OR FOR TECHNICAL ASSISTANCE.