Adding MP3 Player and Upgrading Power Amplifier in PHILIPS CAR 400 - Schematic Needed

Hello. I am going to add an mp3 player to the radio. I got it from China. It has no display, only a button to switch between songs and control from the remote. I need a schematic for the radio, so I would be grateful. I would like this button from the player to try to connect to one of the factory radio buttons. Will it be possible? In addition, I will replace the power amplifier with a stronger one, because 4x6W is not enough.
Best regards and thank you for the hints and diagram

The easiest way is to dump the drive, plug into its audi track, and 3 buttons can be obtained by making a frame with switches for the buttons used for the drive.

Falling off. In place of the buttons there will be a USB socket, an IR sensor and a mini jack socket. I am going to make the front panel from plexiglass, which I would not have to make an additional hole for the remote sensor. My mp3 module is very simple. It has only one button to switch between the following tracks, an IR sensor and a LED that lights up continuously when the track is paused and blinks when playing. It does not have a display, because it is not needed here either. The radio should look as original as possible. It only has a USB socket and a mini jack. If I do not know how to solve the problem with it, the control will be only from the remote control. Of course, I remove the cassette mechanism. I also replace the backlight with blue so that it matches the rest of the car. It looks terribly old in yellow.

Make a key out of the cassette flap. Just attach the switch under the flap - when you press it, you press the key.
By the way, the change from yellow to blue - the tastes are not discussed, but in my opinion it looks only "indulgence" and cheesy (like many products from the PRC). Warm white fits better. But I prefer things in an elegant condition when they left the factory and I can have old-fashioned aesthetic views.

The one with the flap is a good idea, but the inscriptions on the flap will wear off with time, so it probably falls out. : / I don't know if the backlight in Audi or VW cars is related to some tackiness. There are blue / red clocks and entire consoles. Opel even in the relatively new Vectra C has yellow illumination (it may be different in OPC), which I personally do not like. All switches, clocks, and the display are blue, so the radio must also be like that. Only that originally the radio has no power reserve. I will probably install 2 x TDA 7375A in the bridges.

Can I connect the AUX input to the same place as the mp3 player? Separation with separate capacitors at the input is enough, will it be necessary to use a mixer on some TL 072 or something ??

It would be very elegant to use existing keys. However, taking into account that they are in the panel, it is not necessary to put the switch on. There remains a combination system that responds to the appropriate key (in cassette mode the radio does not respond to the search buttons anyway). In addition, if you add a window discriminator system with an appropriate hysteresis, you could use the remote control signal on the steering wheel.
Instead of replacing the power amplifier and then combining it with cooling, lead out the line outputs and connect an external amplifier. It will be easier and definitely better.
So I wonder which Audi is highlighted in blue. In red I agree with white accents also but in blue? And in VW the keys are also not backlit in blue - only the displays. Well, maybe the Hyundai is all blue illuminated. And newer Opel also avoid blue - the red color of the backlight at night makes sense - it's a color that blends in with the night environment. Blue lights at night are not a very good sign.

The most beloved car of Poles - Passat B5. It has blue clocks and red hands. I'm not sure about the rest of the backlight, but since the clocks are blue, I doubt that the rest of the buttons are white or yellow. As for the power amplifier - I do not want to lead out and make my life difficult with cables, so I will install it inside. I have some broken Clarion CD radio with mp3. The tip is functional, I just need to check what's sitting there, how much power. I'd steal the heat sink from him too. The Pioneer I used (and still use it) has 4x27W written on the front (of course there is a proud 4x50 on the front) and it had good power. Everything housed in the radio housing and worked for years. I think more about this AUX input and the player connected to one input.

What is the problem with this AUX - if we have to give two signals to one input, a switch is enough. You can use automatic switching by using any signal from the MP3 module that appears when it is activated.
In VW, as I remember, only the displays and digits on the meter are blue. The rest are in red (i.e. all switches, switches). As I wrote earlier, it is a matter of taste and driving comfort (too much blue can tire a lot at night).

I asked about something else from the two posts above. If a switch were involved, I would have figured it out myself and not litter the forum with nonsense. The design is not to spoil the radio, because in addition to listening, it is also visible to the eyes. Fitting some vulgar switches cannot take place here.

After all, I wrote that automatic switching can be done. When the MP3 player does not work (e.g. after removing the USB device), the input automatically switches to aux mode (I guess it was taken instead of the cassette). It is enough to pick up the signal from the MP3 module informing about the device's operation.
I looked at the diagram from CAR400. There is a matrix-based keyboard. Reading this keyboard is done on the basis of line addressing (i.e. usually putting a low state on it) and checking which column passes this state to the processor (i.e. which key is pressed). By adding a simple combination system (i.e. buffering the state so as not to overload the processor ports and the keyboard itself because it is on rubbers, so the state is soft + key press decoding elements) we have 6 station programming keys and two search keys (they are not used during tape recorder operation) - because I assume that this is how aux is done). By making such a system on a microcontroller (even a simple atiny - we need a total of one port and two to three lines of the second port), you can make very elegant control.
The operation algorithm is simple - the microcontroller listens which keyboard line is checked by the radio processor and which column responds. Based on the line-column combination, it determines which key has been pressed and takes action. It works by:
- selecting the next track (state on the switch),
- selecting another function (i.e. sending your own signal to the remote control receiver)
- AUX / MP3 switching.
It can be done so that the radio will visually look like it was from the factory and gain new functions. And if the USB socket is hidden under the cassette flap, only with the media inserted it will be visible that it is not a factory radio.

I have never played with microcontrollers, nor have I ever played with system programming, so I will probably stay with the remote control. Yesterday I changed the backlight to blue. For the time being, I do not have a meter and I do not know if the diodes are getting the right (not too high) voltage. They shine strongly and the effect is great, but today after turning on the radio, it turned out that one of the buttons is not lit, which worried me. I also fastened the appropriate cables going to the tape deck mechanism so that the radio could sense that the cassette was inserted to use the audio input. Does a colleague have a radio diagram? Could you share?

The diagram is on the forum. You have to download the packed two-piece because the latter is incomplete (only the analog part).

I found. I am adding a link to the video where the guest (I do not know how and why these transistors) used the buttons from the radio keyboard: https://www.youtube.com/watch?v=7Jyjkmrk2vk

Hello. Due to lack of time, the topic is still relevant. I wonder where to get the power to the player. It needs a voltage of 5V. I bought a 7805 1A stabilizer for it, but I am wondering whether I should power it directly from the TDA 3602 stabilizer. However, I do not know if I will overload it. The player has built-in power amplifiers, such as 3W per channel, so of course the power consumption will be a bit higher than if they were not there. Initially, I wanted to power the system from the power point of the tape recorder motor, but here another problem appears, because from the beginning the current efficiency was strangely low there, because the motor did not work. The radio only properly controlled the LED. After plugging in the player, it didn't even squeal. Currently there is voltage there, regardless of whether the radio is playing or I turn on the "cassette" mode. In addition, the BC-640 executive transistor had a CE short circuit. I put in BC-557. Nothing has changed, the power to the motor is still there, but the player does not start. The source button (cassette / tuner) is also not lit. I don't know if this could have any connection.

Power amplifiers from the mp3 player removed, the device currently consumes about 20mA at a voltage of 5V. I think that it can be successfully powered from the stabilizer from the receiver. I will probably not be able to solve the faults of continuous voltage at the power supply output of the tape recorder motor. If the current consumption on the switched off receiver is the same as the factory one (if such a parameter is given), I will forget about the matter. It's a pity, because the power of the mp3 module would turn on with the desire to listen to music from the file, after turning off the tuner. As for the backlight, which shines too much, I have to find a transistor that controls it, i.e. of course executive and change the value of the resistor on the basis. I hope it will work out, because the SMD elements are not marked too much on the OR disc ...

Ps. It turned out that the transistor I put in instead of the BC 560 which powers the motor was soldered incorrectly by me. BC 560 has different markings than 557. After correct soldering, voltage appears only after switching on the tape recorder mode, which is as it should be. At the beginning, however, the player had too little electricity ... It was choking. I connected the engine and it works fine. Now the module plays normally and starts right away. However, the music plays from the microSD card, and ultimately the music is to be played from the pendrive, so the power consumption will increase a bit ... I still don't know much.