5
1
I II
fig. 76
GW 774/1
43
7.20 Removal of printed circuit
boards (PCBs)
Before commencing work on PCB
replacements carry out the following:-
Diagnose that the boards require
changing using the fault finding guide
(see section 8: Fault finding).
•
Turn off the boiler as in section
7.1.1.
•
Remove front casing as in section
7.1.3.
•
Lower front control panel as in
section 7.1.6.
•
Remove back of control box by
undoing the 3 screws (1 and 2,
fig. 65).
•
Disconnect ignition leads from rear
of control box.
7.20.1 Replacement of switch and
control boards
•
Disconnect external wiring from
boiler terminal strip.
•
Unplug ribbon cable from control
board (2, fig. 75).
•
Unplug all leads from the both
boards (1, fig. 75).
•
Pull off switchboard board support.
•
Pull switchboard carefully out of
control box.
•
Push four spring retaining clips (5,
fig. 76) out, and gently lift control
board out of control box.
•
Reassemble in reverse order.
Note:
When refitting the control
board, ensure that the user control
spindles (3, fig. 75) are aligned with
the potentiometer and control switch
holes (5, fig. 75) and that the locating
rib of the potentiometer/switch correc-
tly engages in the groove of the con-
trol knob spindle. Also ensure that
when refitting the main switchboard
the on/off control knob spindle (3, fig.
75) engages correctly into the on/off
switch (5, fig. 75) mounted on the
board.
•
Carry out electrical checks (see
section 5.1)
3
5
N
L
3
4
5
7
8
9
1
2
A
fig. 75
GW 615/1
