Service manual

- alsa apparecchi medicali s.r.l. -

Pag. 14

2)Turn the unit on and, at the end of the self-test phase, check the presence of the following wave form:

(TP “T”)

If the amplitude of signal is different, calibrate the R1 pot on the same board to obtain the maximum

amplitude.

3)Check even if there is a continuous voltage equal to +5.25 V (± 0.05 V) on the TP “U”. If necessary

calibrate the R4 pot on the same board.

Once this calibration has been completed, the functioning range must be as follows:

• With a resistance from 0 to 150 Ω (± 30 Ω) the circuit doesn’t intervene, and the unit works regularly (no

alarm signals or power limitation)

• With a resistance from 150 to 250 Ω (± 30 Ω) the circuit starts intervening. The unit works with the output

power automatically limited (max 200 watt) and the red alarm signal on the front panel flashes

• With a resistance over 250 Ω (± 30 Ω): the circuit works completely. The output power is completely

stopped, and you have all alarm signals (the intermittent acoustic alarm, the red alarm on the front panel

continuously lit up, the code “Err nP”)

The system can be checked using a linear 0-300/500 Ω potentiometer.

CONTROL OF HF LEAKAGE CURRENT

The HF leakage current can be a cause of not desired burning of patients and because of this reason the

Rules state specific requirements and limits (different for units with output circuit completely floating as our

units or circuit reference to earth) to be fulfilled.

These controls can be performed in different ways, all accepted from the Rules.

The first way is with output standard leads, but this system isn’t easy because it is necessary a wide

insulated table able to contain the unit, the instruments needed and the output leads completely laid straight.

In this case the limit accepted is a leakage of 150 mA.

The second one, useable only for the monopolar section of the ESU, is the easiest because is performed

directly at the unit terminals with the output leads as shortest as possible and so the insulated table can be

smaller. In this case the limit accepted is a leakage of 100 mA

In every case this control must be performed according to the following general warnings :

- All different test conditions must strictly respect the specific requirements detailed in the section 19.3.101

(point a) 2, a) 3, b), c)) of the International Standard IEC 60601-2-2

- The testing instruments are extremely important because can produce big errors of reading.

For example many automatic testers require the contemporary connection of all cables needed for the

test (active cable, neutral plate cable and “cable used to do the measure”). This kind of connection

doesn’t allow to respect (performing the test with output leads) the requirement of the distance among

leads (between active and neutral lead 50 cm, between active or neutral lead and lead needed to do the

measurement 25 cm) and produces a not real increasing of the leakage.

Because of this reason it is, at least, necessary to use this kind of instruments checking if the value

detected following the Standard Use manual of instruments corresponds to the value detected fulfilling

the testing requirements of the Rules that state as necessary a distance of 50 cm. between active and

neutral plate cables. Practically that means, using an automatic tester:

“to have a correct reading it is necessary to disconnect from the instrument the cable opposite to that

tested”