Ultrasound Technologies PD1 series, Service Manual

Page: 19 / 75

Ultrasound Technologies Ltd
5.0
1 0
Fault finding guidelines
This section is an aid to trouble shooting and should be used in conjunction with the relevant circuit
diagrams found at the rear of this manual. In each case the re calibration must be carried out after any
repair.
The following tables list some of the symptoms and the relevant circuit areas.
NOTE Do not, under any circumstances attempt to repair the instrument whilst it is connected to
a patient.
Symptom Suspect Circuit Check
Unit does not switch ON Remote switch on front panel J1 pin 1 goes low when
switch is depressed
U1 ON/OFF Control Output goes low when switch
is depressed
Battery J1 pin 1 > 7V
Battery Low LED on
permanently
Battery condition J1 pin 1 > 7V
Replace battery
U3 Comparator See test / calibration section
Excessive battery drain U1 / Q2 ON/OFF Control Q2 must switch when switch
is depressed.
Change battery
Ultrasound OK but no audio Transducer position Re position transducer
Crackling operation of volume
control VR1 Replace volume control
Broken conductor in cable Check audio signal on pin 3
of U2
Headphone socket SK2 Audio signal on J3 pin 1
Replace loudspeaker
Unit unstable Ultrasound transducer Check output drive into
crystal is 1.5V pk/pk.
Check received signal in
transducer J1 pin 4, signal
should be a low frequency
audio signal approx. 2Vpk/pk.
Replace transducer.
©Ultrasound Technologies Ltd Page 15 of 32
PD1 / FT120 service manual Issue 3 January 2007