Wallwasher circuit description

The following is for information only and cannot be guaranteed to be 100% accurate - it’s possible that there may be some connections missing between components. However, if there are, there shouldn’t be many and the details provided here should be a help in understanding the operation of the wallwasher or for fault finding.

The wallwasher circuit can be divided into different self-contained sections and this is the way that I have done it. Although one circuit covering everything may possibly make it easy to follow something at a glance, the fact that the circuit has been split into sections means that the diagram can be larger than would have been possible otherwise. This means that the diagram for each section can easily fit onto an A4 page for printing. The diagrams are available to download, in PDF format, from the Downloads tab.

A few components do not have a number printed on the PCB. I have allocated them a number as shown on the Unmarked Layout diagram.

The PCB also contains some components that I have not been able to find the data for, particularly the transistors. One component is 1028 / 1029 / 1032 / and 1039. These have a printed code of 7BXXX. The XXX can vary - e.g. 7BNAK, 7BNAY etc. The purpose of these in the circuit seem to be as a switch (switching transistor?) and are used to turn different sections of the power supply on and off. On the diagrams, I have shown these represented as a transistor symbol - the base being the control (to turn the “switch” on and off) and the collector / emitter being the switch contacts. If anybody can identify this component, then I’d be glad of any information.

Unless stated otherwise, the information is for the wallwasher PCB. The external devices (and wallwasher lights) have their own tab. Information for them and circuits can be found there.

The circuit is divided into the following sections:

Internal power Supply

Fans interface

Rumbler interface

Wallwasher lights interface

Sidelights and speakers interface (including subwoofer relay)


LED driver

Connections between sections are easily identified. Other than connections to the external devices (via the wallwasher sockets) the connections are generally to the power supply or CPU or, for the lights, the LED decoder.

Unless a specific voltage is mentioned, assume the voltage to be approximate.

A description of the circuits is given below. Please let me know if I’ve got something wrong.

I recommended that you download and print the circuits as it makes the descriptions easier to follow.

If you want more information on any of the integrated circuits, such as the CPU and LED driver, please see their data sheet - available via the links page.

Internal power Supply

Circuit description

18v in

18v DC from the external PSU passes through the black square component marked on the PCB as 1101/1102/1103. I am not quite sure what this is. I did wonder if it was a bridge rectifier, but can’t see the point of it, unless it’s for polarity protection. When the continuity is tested, there is virtually a zero Ohm reading between the input socket GND and the PCB GND and between the input socket +v and 1011 - as if the component was just a link. I suppose it could be a choke.

1011 is a resettable 3A fuse. This will open and break the circuit in the event of an overload and close once the overload has cleared.


I’m not sure what the purpose of 1022 and 1020 - 1024 are. 1022 provides the always on Vmain and, as far as I can see, is permanently switched on.  


Vmain is always on as long as a working PSU is connected to the wallwasher.

It provides the 18v input to the 3v3 (7021) and 5v (7010) regulators.

Vmain also goes to the sidelights, being switched on and off to the sidelights via 1032 and 1039


Vsw is the 18v that goes to the rest of the wallwasher circuits. It is the main source of power for the rumbler, fans and wallwasher lights. When the wallwasher is in standby, Vsw is 0v.

1028 switches Vsw on and off under the control of the CPU.

The red LED is fed from Vsw and lights when Vsw is on. If the red LED is on, this is normally an indication that the wallwasher PSU is good and that the wallwasher is not in standby. Unfortunately, the LED is not clearly visible when the wallwasher case is on, but the reflection can usually be seen if you look into the wallwasher through the gap at the bottom of the front of the case. (You should also be able to see the flickering light from the green LED when the wallwasher is on).

I’ve shown all the components that connect between the supply and GND on the one diagram for clarity. Some of the components may be repeated on other diagrams.


18v is quoted as a general voltage. In fact, the voltage drops slightly as it goes through the circuit and may vary slightly depending if the wallwasher is in standby or ON (when there is also a sight voltage drop). It also may vary slightly from PSU to PSU.

As a rough guide:

18v In can be 18v7

Vmain can be  18v7

Vsw can be 18v5

A few tenths of a volt difference is nothing to worry about.

3v3 and 5v supply

As both these regulators are fed from Vmain, the 3v3 and 5v supply in the wallwasher will be permanently on

As can be seen, not everything is off when the wallwasher is put into standby. The CPU, LED decoder and sidelight circuits are all permanently on and so the wallwasher is still drawing current. The PSU itself is also drawing current. As shown on the Power supply page, this current is equivalent to about 2kW a week, just by leaving the wallwasher in standby 24 hours a day.

Fans interface

Circuit description

There are two fans - left and right. Most of the fans circuit is duplicated.

Vsw goes to variable voltage regulator 7026. The output voltage is set by resistors 3053 and 3055 and is approximately 9v5. I have called this Vfan.

Vfan passes through an inductor and via link 8011 to each fan circuit. Capacitors smooth Vfan.

I will use the right fan circuit as an example, both circuits are the same.

Vfan goes to FR+ via resettable fuse 1016

The CPU (pin 37) controls FANT1. This switches GND on and off to FR-, providing a voltage of 9v5 to the fan motor.

When the fan is plugged into the wallwasher socket, it shorts 2 and 3 (GND and Detect) and thus pulls CPU pin 21 to GND.

6024 and 6036 provide ESD protection.

Rumbler interface

Circuit description

The rumbler circuit is basically the same as the fan circuit, with different component values.

The wrist rumbler has two motors, which I’ve designated left and right.

Vsw goes to variable voltage regulator 7027. The output voltage is set by resistors 3054 and 3056 and is approximately 12v. I have called this Vrum.

Vrum passes through an inductor and via link 8012 to each motor circuit. Capacitors smooth Vrum.

Although the circuit is the same as the fans circuit, for some reason the R+ and L- connect to one part of the circuit and L+ and R- to another instead of being nicely self-contained!

I will use the path to the right motor as an example.

Vrum goes to R+ via resettable fuse 1019.

The CPU (pin 35) has a pulsing output which controls 7025. This pulses GND on and off to R-, providing a pulsing voltage to the right rumbler motor. When measured, the voltage will be continually varying between around 11v to 12v.

When the rumbler is plugged into the wallwasher socket, it shorts 4 and 5 (GND and Detect) and thus pulls CPU pin 15 to GND.

Wallwasher lights interface

Circuit description

All three wallwasher light circuits are the same, I’ll describe the right circuit.

Connection to the wallwasher light PCB is via a 14-way socket.

The Blue, Green and Red LED inputs come from the LED driver (7006). The inputs are protected against ESD via 6007 and half of 6010 (although I can’t find any ESD protection for the left red input!).

Vsw goes to pin 1 and pin 9 is the sensor output from the wallwasher light PCB to the CPU.

Pin 11 is used for detection. When the light is plugged into the socket, pin 11 is connected to GND via the wallwasher light PCB and thus pulls CPU pin 18 to GND.

Although the wallwasher lights are detected individually, if one light is removed, the other two may not be detected in DirectControl.

Refer to the wallwasher light circuit for details of the light PCB

Sidelights and speakers interface

Circuit description

I’ll refer to this as the sidelight circuit interface, although it also contains the interface for the speaker side of the lights with speakers (speakerlights). If a sidelight is plugged into the wallwasher, then the additional interface used by the speakerlights is ignored because there are no connections to it on the sidelight plug.

Lights section

The sidelight interface contains more components than the wallwasher light interface. Presumably this is because the signal needs boosting to travel the longer distance to reach the sidelight.

There are two sidelights - Left VGA and Right VGA. Both circuits are the same so I’ll describe the right one.

The circuit for each of the three colours is identical. Looking at the red circuit, it can be seen that the output from pin 10 of the LED decoder goes to op/amp 3060 and the output from 3060 goes to pin 2 of the VGA socket. Each colour output has a corresponding GND connection - pin 3 in this case.

The light sensor output from the sidelight PCB goes via socket pin 8 to CPU pin 29.

The sidelight is detected via socket pin 12. This connects to GND via the sidelight PCB and thus pulls CPU pin 19 to GND.

The 18v to the sidelight PCB, via VGA socket pin 1, comes from permanently on Vmain. 1032 (left) and 1039 (right) switches the 18v on and off. Switching is not controlled from the CPU, but instead is controlled according to whether the sidelight is detected or not. This is because the PCB needs current for the LED drivers before the LEDs will work. Therefore, the LED driver circuitry needs to be ‘live’ before the CPU turns the LEDs on. One disadvantage of this is that these circuits are always on, even when the wallwasher is in standby.

Using the left as an example:

When the light is not plugged in, 1037 is off (there is no GND path from the emitter). Resistor 1034 pulls 1032 pin 3 high. 1032 is turned off.

When the light is plugged in, there is a GND path from the emitter of 1037 via pins 9 and 12 of the plug. 1037 is turned on, connecting 1032 pin 3 to GND, turning on 1032. This switches on the 18v to VGA pin 1.

Speakers section

The VGA Left socket pins 10 and 11 are directly connected to Audio In socket pins 2 and 1. The VGA Right socket pins 10 and 11 are directly connected to Audio In socket pins 3 and 4. Pins 10 and 11 connect to the speakers inside the speakerlight. When the Audio In plug from the subwoofer is connected, Pins 1 and 2 and pins 3 and 4 on the Audio In socket directly connect the amplifier output in the subwoofer to the speakers in the speakerlights.

Audio In socket pins 5 and 6 are connected to the mains relay inside the subwoofer. Pin 6 is the positive supply, pin 5 is a switched GND which is switched on and off by 7008 under the control of the CPU. There is no detection in the Audio In. As long as the wallwasher is on, then 5v is normally present between pins 5 and 6, whether the plug is connected to the Audio In socket or not.

Voltage readings

Measuring the relay output.

To measure the 5v for the relay output, this MUST be measured between pins 5 and 6.

For some reason, Philips label the connection on the amplifier PCB from pin 5 as STBY, which I assume means standby. However, when the wallwasher is in standby, there is no GND at pin 5 and so the reading between pins 5 and 6 will be 0v.

Measuring the internal 5v supply

As can be seen on the diagram, pin 6 is directly connected to the internal 5v supply, which is permanently on. As a consequence, pin 6 can be used to confirm that the internal 5v supply is available. This, in turn, will confirm that the PSU is working OK. To measure the 5v internal supply, connect a meter between pin 6 and a ground source - such as a socket shell, rumbler socket pin 4, etc.

Control connections

VGA socket pins 13, 14 and 15 are connected to the speakerlight control PCB and form the data bus that links the CPU to the control.

LED Decoder

7006 - TLC5941

7006 takes the serial data from the CPU and decodes it into the fifteen different light outputs for the sidelights and wallwasher lights. Strictly speaking, it is classed as a LED driver as the outputs can drive LEDs directly. However, as the output for the LEDs requires further buffering / driving for the amBX use, I have called this the ‘LED decoder’ and the and called the additional driving circuits the ‘LED drivers’ to save confusion.

Pins 2 - 6 and 23 - 25 are the data bus from the CPU

Pins 7 - 21 are the fifteen outputs

7006 is fed from the 3v3 supply and is always on

Central Processing Unit

7020 - C8051F345

7020 is the control centre for the amBX hardware. Although it has some independent built-in actions, most of what it does is based on what the amBX software tells it to do. Simply put, the software on the PC works out what lights should be on, how bright etc. and whether the fans or rumbler (if connected) should be on or off. This information is sent along the USB data bus to the CPU where it is decoded.

Additional connections - via UART debug socket 1003 and Jtag debug socket 1008 - are provided to allow the CPU to be programmed or debugged.

7020 is fed from the 3v3 supply and is always on.

Apart from the data buses, there are various other connections to the CPU and some of them and their operation are described below. Many of the pins act as inputs, with either a high (normally around 3v3) or low (normally 0v) state. A change of state is detected by the CPU and the CPU will act on this change. An example of a change of state is when a device is detected as connected. Other pins act as outputs and are used to turn the devices on or off.


When the side switch on the wallwasher is pressed, this toggles the wallwasher between ON and standby.

Pin 3 is pulled up to 3v3 via 3083. When standby switch 3084 is pressed, this pulls pin 3 down to 0v, which returns to 3v3 when the switch is released. This creates a negative pulse. Holding the switch in will not make any difference.

If the wallwasher is in standby, the pulse at pin 3 will cause pin 32 to be high, which turns on 1029 and so turns on 1028 and switches Vsw on. 18v will now be present at Vsw and the wallwasher will be on.

If the wallwasher is on, the pulse at pin 3 will cause pin 32 to go to 0v. 1030 pulls the base of 1029 to zero, turning 1029 off. As a consequence, 1028 will now turn off and Vsw will go to 0v. The wallwasher will be in standby.

When 1029 is off, resistor 1027 pulls 1028 pin 3 to around 18v

When 1029 is on, there is a path from pin 3 to ground

1028 switches on when the voltage at pin 3 is low, off when it’s high.

A poor contact on the switch may cause “switch bounce”. This is the equivalent of pressing and releasing the switch several times very quickly. If the switch remains stuck in, then this can cause problems as this may cause the wallwasher to permanently remain in standby. If this is suspected, simply unplug the switch from the PCB. The switch doesn’t have to be connected for the wallwasher to work as the wallwasher defaults to ON when the PSU is first connected / switched on. All it means is that the wallwasher can no longer be put into standby (unless you have the speakerlights).

Device detection

When a device (sidelight / speakerlight, wallwasher light, fan or rumbler) is plugged in, this is detected by the CPU. The method of detection is simple. The relevant CPU pin is held high by a 100k resistor to 5v. The pin is shorted to ground when the device is plugged in. The short is either made via a connection between two pins in the plug (rumbler, fan, sidelight) or via the PCB (wallwasher light).

This is why it is important that if you are replacing a plug on a device, or are connecting your own device, you make sure that you also make the short circuit between the relevant pins.

Device on / off

The fans, rumbler and subwoofer mains relay are switched on by the relevant pins on the CPU going high, which then turn a transistor on, connecting the device to GND.


Each of the lights has a light sensor (photo resistor) on the PCB. Depending on the brightness of the lights, this gives a varying voltage on the corresponding CPU pin. I’m not sure if the sensors are actually used or not.

Speakerlight controls data bus

Pins 5, 44 and 45 are the data bus that connects to the right speakerlight controls PCB for the volume control, brightness control, standby switch and blue standby LED.


Pins 8 and 9 are used for the USB data bus, which transfers the data between the PC and the wallwasher. Pin 12 connects to the USB 5v and is used to detect if the USB is plugged into the PC. If this 5v is not detected, the wallwasher cannot be turned on and will remain in standby.

Note - the USB cable could be connected to an external USB supply (such as a mobile phone charger etc.), and this will allow the wallwasher to be switched on. However, the wallwasher also uses the data bus as an additional means to detect that the USB is plugged into a PC. If the USB is connected to an external 5v source, the wallwasher may be on, but it cannot be guaranteed that everything works as it should. For example, there will be no 5v supply to the subwoofer relay.

Activity LED

The output from pin 28 connects to the green LED. I’m not quite sure what the purpose of this LED is. I assume that it’s just a diagnostic aid. It always flashes when lit. I call it the ‘activity LED’. In normal circumstances, I have always found the green LED to be on when the red LED is on - e.g. when the wallwasher is on. The green LED is off when the wallwasher is in standby.


At present, I cannot find anything that connects to pin 24, even though there is a PCB track (and through hole) coming from that pin. It would appear that pins 31 and 41 are Not Connected.