Apparently the TEF6686 module has better performance than the TDA7786 - e.g. 7786 poor sensitivity, selectivity, multipath issues etc. My JY TDA7768 is terrible, even with an RF amp, so to find out if the TEF is any better, thought I would try and investigated swapping tuner modules. Reviewing the GS board I have as a spare part against my JY, I identified the modules are pin-for-pin compatible.
Sucessfully swapped the Radio module from a donor GS board containing a TEF6686 Module into my JY board originally containing a TDA7786. The GS board was quite difficult to unsolder the module, perhaps due to leadfree solder, fortunately the JY board was easy, the desolder wick readily desoldering the module.
As for results, I have bench tested and RDS, tuning, audio etc is OK, I am yet to test in the vehicle. Will update this thread with results.
See attached images. Note that the JY case had additional mounts that over time might short out against the non-ground PCB tracks, resulting in complete failure of the unit!
Welcoming any questions.