Luxman R-115 FM Radio Issues

[Richardjhy]

Recently acquired a Luxman R-115 and found it having issues with FM Radio. Autoseek won't find any stations. I can manually tune all stations I like but none of them are in stereo mode, even the ones with strong signal. I carefully checked the FM/AM radio board with magnifier and found nothing abnormal. Solders are all OK and seem original. Google AI told me that issues should be with 19khz pilot tone. Does anyone has a clue?

BTW, how to remove front face cover? Tried removing top and bottom screws and knobs but face cover can't be removed.

Thanks!

 

[AnalogSteph]

Probably a detuned discriminator coil, as so often the case. The adjustment is very delicate so a slight drift is not overly surprising. Finding the zero crossing hundreds of kHz away from nominal frequency may however indicate a corroded titanium capacitor inside the can (kind of the modern version of silver mica disease). If it's bad the only fix may be removing the often black and crumbing capacitor remains and soldering an external capacitor of NP0 or -30 ppm/K type on the underside of the board (91 pF seems to be a common value).

I have seen the VCO adjustment drift so far that the stereo decoder was no longer decoding anything, but it's quite rare. Plus, this receiver is from 1988 so may be using a ceramic discriminator anyway.

 

[Richardjhy]

Probably a detuned discriminator coil, as so often the case. The adjustment is very delicate so a slight drift is not overly surprising. Finding the zero crossing hundreds of kHz away from nominal frequency may however indicate a corroded titanium capacitor inside the can (kind of the modern version of silver mica disease). If it's bad the only fix may be removing the often black and crumbing capacitor remains and soldering an external capacitor of NP0 or -30 ppm/K type on the underside of the board (91 pF seems to be a common value).

I have seen the VCO adjustment drift so far that the stereo decoder was no longer decoding anything, but it's quite rare. Plus, this receiver is from 1988 so may be using a ceramic discriminator anyway.

Thanks. Is L001 detuned discriminator coil? The IC is LA1235.

L001 on P.C. Board:

 

[Richardjhy]

As per service manual, tried adjust L001 PRI and FM stereo is back and FM autoseek is working now. I don't have a scope so didn't bother to adjust L001 SEC.