Tait T850 II Series, Service Manual

Page: 75 / 370

M850-00
T855 Fault Finding B5.1
Copyright TEL 31/09/98
5 T855 Fault Finding
Caution:
This equipment contains CMOS devices which are susceptible to dam-
age from static charges. Refer to Section 1.2 in Part A for more infor-
mation on anti-static procedures when handling these devices.
The following test procedures and fault finding flow charts may be used to help locate a
hardware problem, however they are by no means a complete fault finding procedure.
If you still cannot trace the fault after progressing through them in a logical manner,
contact your nearest Tait Dealer or Customer Service Organisation. If necessary, you can
get additional technical help from Customer Support, Radio Systems Division, Tait Elec-
tronics Ltd, Christchurch, New Zealand (full contact details are on page 2).
Note 1: In this and following sections deviation settings are given first for wide
bandwidth sets, followed by settings in brackets for mid bandwidth sets ( )
and narrow bandwidth sets [ ].
Note 2: Unless otherwise specified, the term "PGM800Win" used in this and follow-
ing sections refers to version 2.00 and later of the software.
Refer to Section 6 where the parts lists, grid reference index and diagrams will provide
detailed information on identifying and locating components and test points on the
main PCB. The parts list and diagrams for the VCO PCB are in Part E.
The following topics are covered in this section.
Section Title Page
5.1 Visual Checks 5.3
5.2 Component Checks 5.3
5.3 Front Panel LED Indicator 5.3
5.4
5.4.1
5.4.2
5.4.3
DC Checks
Power Rails
VCO Locking
Mute Operation
5.4
5.4
5.4
5.4
5.5
5.5.1
5.5.2
5.5.3
5.5.3.1
5.5.3.2
5.5.4
5.5.5
RF Checks
VCO Frequency
RF Sensitivity
Oscillator Stability
TCXO
Second IF
Demodulator Output
IF Distortion
5.5
5.5
5.5
5.6
5.6
5.6
5.6
5.6