Vaillant ecoMAX 646 Service Manual download pdf (Page 43)

fig. 76

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43

7.20 Removal of printed circuit

boards (PCBs)

Before commencing work on PCB

replacements carry out the following:-

•

Diagnose which board requires

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 from control panel as in

section 7.1.6.

•

Remove back of control box by

undoing the 3 screws (1 and 2,

fig. 65).

7.20.1 Replacement of main

switchboard

•

Disconnect external wiring from

boiler terminal strip.

•

Unplug 2 ribbon cables from

control board (2, fig. 75).

•

Unplug all leads from the main

switchboard.(1, fig. 75) and lift

switchboard carefully out of control

box.

•

Reassemble in reverse order.

Note: When refitting the main

switchboard ensure that 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)

7.20.2 Replacement of control board

•

Unplug 2 ribbon cables from

control board (2, fig. 76).

•

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 (a, fig. 75) are aligned with

the potentiometer and control switch

holes (b, fig. 75) and that the locating

rib of the potentiometer/switch

correctly engages in the groove of the

control knob spindle.

•

Carry out electrical checks

(see section 5.1)

fig. 75

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