Punto (Mk2/2b) Upgrade Punto 188 cassete radio

Hey man, great post!

I don't understand how you can get 3.5mm jack connected to the back of the HU?

Do you take the wires that were originally for the cassette?

Hi! Thank you for compliment!

I connected wires to the capacitors. They locate between tape pre-amplifier and source selector. They are 10 uF (IIRC).
But this system has a little bug. You need set volume to the maximum at your mp3-player. Or you need make a pre-amplifier (2x-4x depend of player).
And you need make connection at the tape-mechanism power connector. But I forget what pins you need close. Pins corresponds PLAY mode.
I made it more than year ago. And I forget some details. Sorry.

brilliant Stason i understand it now
you made the slide to make the sat nav more removeable
i couldnt work that bit out but see you used the 12 volt from the radio cassette to power it rather than using the cigarette lighter
as regards using your mp3 player through the pickup of the cassette head then you must be possibly losing power in the audio lead from mp3 to pre amp for tape head
as you say another basic pre amp which can be bought for pounds from ebay would do this
my only concern as always is tape heads have the pre amps set to a certain bias and as such if used for other uses tend to sound very trebly
brilliant invention though and looks really neat

I didn't use the original preamp because it has pre-distorsions for magnetic head. It has low impedance but, as you said, sound was awful. I connected after the original preamp. But you must have good impedance match. Using your own linear preamp is good idea.
First my idea was to use another special platform with mp3-player only.
The first player I bought was awful. It had line out. But it wasn't be able remember the last song when I switched it off. And begun from the first song always. Of course I can not use it for audio books. The second player swallowed the first seconds of every song. And now I use player gifted by my friend. It works good at the maximum volume. I don't use preamp. But preamp using will give the better sound.
Note. If you will use player with LCD, you MUST USE preamp. LCD gives a digital noise. You will listen it, if your amplifier has high impedance and your player use maximum volume.

So I installed mp3-player into the radio.
I was hoping it would happen earlier, but the Chinese mp3-player sent rejection (had re-order).
Experiments have shown that the line-out signal level from the Chinese modules was not enough. An optional amplifier was required. At first I wanted to re-order the same player and make a transistor amplifier (h21 >= 75 was fine), but I found ZE-CT08A module at dx.com site (sku 163168), which I ordered.
This module does not have a radio (it is just not needed), but it has a headphone amp (and it just needed). The module costs about $11
Of course, I wanted to keep the ability to insert the platform into the cassette hole. But where can I attach the display and inputs? And how to put four regular buttons on the front panel?
Here began work.
I decided to put inputs in place rewind buttons, and to put the display on the flip cassette cover (although it have 12 wires). IR-receiver the same way (it have three wires). Basic buttons suggested itself under a big round key (besides, it does not need in TAPE mode).
I approved such project for myself.
Firstly I made the keys module. There are PREV and NEXT at the top. There are Pause and Mode at the bottom (they are hard to see). All of this can be removed, preserving the appearance and functionality of the radio.

There is a good powerful 5V power supply for processor and USB on the module. Of course, it is reasonable to use to charge the devices via USB. But it is not managed externally, and when the module is working it supplied USB and processor simultaneously. It turns out that device can only be charged in TAPE mode. It is not convenient.
I decided to feed the processor separately, and USB - separately through the stabilizer. Processor with SD-card consumes about 40 mA, and to power it, I used IC 78L05 (Now I know, that 7805 is better, else you must use a small radiator), connecting it to the tape transport motor power line. Voltage there appears only in the TAPE mode (it is very convenient). To share power you need to remove the element L3 from the board and solder power wire to the pad at the processor side. USB is powered while ignition is on or until the radio is not turned off. For this case stabilizer input is connected via a relay to the car battery. The relay closes by a signal from the ignition, or by a signal for the radio antenna amplifier. I used the relay "I have" - 5 V (with ballast resistor in series with the winding). It switches the current up to 1 A.
It is control signals and audio signals connection.

This is modules holder.

ZE-CT08A have SMD output capacitors C35 and C39. For bass increase you need to use 20-500 uF electrolytic capacitors instead them. I used 22 uF.

Now the fun part - the display.
I built a new cover made of clear plexiglas 2 mm. I stuck a piece of filter for studio lighting with double-sided tape. The result was a gray color, almost like a car radio (incidentally, input plate is made by the same way). I put another layer of the filter between the filter and plexiglas, that display and IR receiver not to be seen. (Now I know, it was wrong. Information on the display is becoming not visible in the sunny day. One layer is enough.) The result was a dark gray bar (did not think about the symmetry). Display stuck to the plexiglas with the hot melt, and IR stuck to the display the same way.
How can I lay 15 wires (display and IR receiver)? Even very thin insulated wires were thick. Long thought and suddenly - eureka! Lacquered winding wire! As simple as that! They also fit into the soft insulation from the wire.

Here is the assembled player inside the radio. Thus, as you can see, it is possible to insert the card and always carry your music with you. Replace the card - no problem. You take out the radio, take off its cap, replace the card.

The cassette cover in the lowered position.

The cassette cover in the rised position.
I had to make a cut in the plastic front panel for the display. And also remove one fastener (of six). And I had to cut out a piece of the metal frame of radio.

Test player with 16 GB USB-stick. Search time when you turn on a flash drive about 5 seconds. (There are a little more than 780 songs)

Standard radio mode. Power to the CPU is not forthcoming. The display is not lit. But you can charge anything.
The remote control is attached to the player and extends its capabilities. You can directly enter the number of the desired song or skip the folders. And also change the equalizer settings.
The basic functions work without the remote control. The left side of the big round button is previous song. Right is next. Up Arrow is pause. Down Arrow is mode (SD-USB-AUX)

Now it completed project.