Blaupunkt MR23 drive belt replacement.
Old stretched drive belts are a common problem on the MR23. When you put a tape in, the unit tries to play it but just flicks from side A to B and ejects the tape. This little repair should sort out the problem. It worked for me at little cost. Luckily it is an easy fix. Here's how I did it.
Firstly, remove the top and bottom covers. Ease the cover upwards at points A and do the same down the sides. The cover is lipped under points B.
Undo these 3 screws. It's wise to put a little Blu-tac on your screwdriver when removing the countersunk screw to grip it as it's a bit fiddly and can drop inside the unit.
De-solder these 3 red wires, taking note of where they came from.
De-solder the blue and purple wires again taking note of positions although the PCB is marked BL-blue and VI-violet.
Disconnect this multi plug.
Carefully flip the unit over and remove this last screw. The cassette chassis and PCB should now be free. Just lift up the back edge where the 2 slotted screws were removed and the whole assembly will slide out rearwards.
With the tape assembly removed, you can get to the pesky drive belts. After taking off the small outer belt, undo the 2 screws that are arrowed to allow the larger inner belt to be removed. Using a copy of the Derbyshire Times to protect your dining table is of course optional.
Take the old belts to your local electronics shop and ask for replacements that are a little smaller, Remember, the old ones are stretched.
Ensure that when you fit the new inner belt that it follows this path. With the new belts fitted, refit all parts in the reverse order of this guide. It's wise to leave the upper cover off for now.
The red arrow shows the speed control potentiometer for the cassette motor. I found that this needed to be adjusted due to the new drive belts. Reconnect to the power and speaker wiring in your car and put a tape in. If it plays too slow or fast, adjust the potentiometer. Do this very carefully and don't short out anything on the PCB or other components.
When satisfied, replace the cover and jobs a good 'un. This procedure should be similar for other Blaupunkt cassette players of this era like the Cambridge M23 etc.