HuiFei - 2 DIN Pure Android car radio: radio modification



I have purchased a Chinsese 2 DIN head unit for my car.

Unit works great, except the radio quality was bad.
-> Meaning you could not hear any high tone...
When playing CD, GPS ... and other sources everyting crystal clear.

It appears there is a calculation error in the band filter ( low pass filter part ) that goes from Radio Tuner IC to ... (rest of circuit)

I was inspired by a Russian document (not mine) that describes this problem for another unit. My unit had the same problem, but a different PCB. I added an English translation (with google translate).

So here is my (hand drawn) schematic of my unit, with calculations.

I replaced C240 appr...58nF (measured +-5% error rate)  with 1nF
With the original cap, cutoff would be 442Hz(!) FM radio goes to around 15000Hz
With 1nF cutoff would be 25,6kHz.

The caps are on the underside of the main board.

The two new caps in place. C240 and C236 are replaced: (I moved R246 a little bit, excuse they are small parts)

Model: KYD-3000 MB