Loma IQ2 Service Manual page 86

SEARCH HEADBOARD REMOVAL & REFITTING
Located behind the removable end plate of your detector search head case is a
further electronics board. This board supplies the drive to the central transmitter
coil and initially processes the signals received from the two symmetrical
receiver coils.
Since every board is customised to suit the particular detector it is fitted into,
there are a variety of components that must be checked, and possibly swapped
between the old board and the new board. There are also two power rails that
will need to be checked and adjusted as required. If Loma has provided the
board for a specific serial numbered detector then some of these components
may already be correctly fitted.
This section serves as a guideline for replacement of the detector search
headboard. While working with the circuit board an antistatic wrist strap should
be worn.
The process described seeks only to cover the minimum requirements needed
to ensure a successful board replacement and does not cover the full set up
process. Once completed the detector will be functional, however if any fine
adjustment is required, which may be indicated by a slight loss in performance
then contact your local Group Service Centre to arrange a service call.
The components that must be checked to ensure a successful board
replacement are described in the
is shown in
the wiring connections in
OSGO
Tx output
Tx gnd
Fixing holes
+ 12 volts
A gnd
- 12 volts
Ctrl 3
R out
Sig gnd
X out
Module 8023
replacement paragraphs
Figure 6 the mounting arrangement in
below
Figure 8
on page 17
L1 copper case
Frequency
Selection Links
L1 fixed value
TP4
+Vo
IC17
Metal Spacer
fits here
C24
R41
R44
TP2
R35 R34
C23
Figure 6 Search Headboard
on page 18
Figure 7
all in this section.
Crystal
Low frequency
not used
11-12
9-10
7-8
-Vo
5-6
3-4
1-2
High frequency
Ctrl 4
IC15
R51
Ctrl 2
Ctrl 1
JP1
R R
D D
5 3 1
2 3
I I I
6 4 2
RF input
RF gnd
Balance
Maintenance
. The board
with
on page 17
R
D
1
6-16