Firmware problem with Chinese Mini TEF6686 by C3

[Dr-InSide]

Hi.

I have the Mini TEF6686 by C3. It had Chinese firmware on it, and I couldn't read the menu. So I tried using original TEF6686_ESP32_v220 Firmware. The display was rotated 90°. Then I tried the ARS firmware, but the display was upside down and inverted. I fixed this with Mode and BW+Band when switching on.

Now the radio can be operated, but there seems to be a frequency offset of -1435 KHz set on AM (e.g. Ch.292 from 6070 KHz can be found at 4635 KHz). Furthermore, I cannot find any stations on FM (possibly also a frequency offset?).

It has a tuner module from BYD labelled ‘HAC Radio Module 128’ (translated).

Does anyone have any idea how I can fix this problem?

Thanks!

[andimik]

Better to ask this on discord, as this is not an issue of the firmware.

https://discord.com/channels/1053804249651359765/1053804431721898056

[PE5PVB]

Looks like the wrong crystal frequency was set.

[Dr-InSide]

Thanks for the quick reply!
Ok, to change the crystal frequency, do I need to change it in the source code? Where?
And the big question: how do I determine the correct frequency?