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THE PRINTED CIRCUIT BOARD (PCB)
MOST IMPORTANT – MISTAKEN PCB’s
Both the Feb-20E (later models) and the FEB 24E use a PCB with a common chassis.
Both Boards look identical to each other until closer inspection. There is a potential for a
boiler to be fitted with an incorrect PCB. No damage or danger will result from this mistake
– the boiler simply will not work.
If a FEB-20E PCB is fitted to a FEB-24E boiler the following will occur:
1. With jumpers S1 and S2 open – no green or red LED’s will work
2. With jumpers S1 and S2 closed – green LED off and red LED will display fault 2
To identify the correct PCB please observe the following rules:
1. The main EPROM chip (position 5 in photo) contains the software for the boiler. All
FEB-24E boilers run on chips marked “control 205” or “control 204”. The
identifying labels on the chip are either blue or yellow with a small number of boards
containing chips with hand written white labels.
2. Identification of the FEB-24E PCB can also be achieved by locating the number
“N03G009M8” on the large transformer. This will also be marked with “control 205”
or “control 204”.
DESCRIPTION OF THE PCB
While the PCB can appear complex and difficult at first, understanding its operation and
how to test voltages can result in a speedy resolution of any problems.
The next few pages will guide you through the basic operation of the PCB without the need
for a degree in electronic engineering. A basic knowledge of electricity and a digital multi
meter will be the only requirement for diagnosing possible faults without damaging the
PCB or yourself.
The golden rule when working on the PCB is not to allow mains 230V ac to enter the low
voltage circuit i.e. via the room thermostat or the time clock. Care must be taken when
reconnecting terminals on the time clock if they have been disconnected as all the
terminals are of a standard size. It is possible to connect the 230V ac motor supply for the
clock to the 24V dc control circuit. It is also important to isolate at the mains supply and
check that no power is present at the appliance before carrying out work or changing
components. This will eliminate any possibility of creating a short circuit to earth, which
even in the case of low voltage 24V dc components e.g. high limit thermostat will cause
damage to the PCB if allowed to short to earth.
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