Sony ST-S333ESG tuner no audio output

[bx19]

Noticed that this is an amplifier forum. Hoping the expert here can help me on my Sony ST-S333ESG AM/FM tuner. Circuit diagram found, hoping somebody can help to narrow down the problem area.

Problem:
(A) No audio output.
(B) Auto tuning unable to stop when a signal is present.

Observations:
1. No audio output on L and R channel. The built-in audio CAL tone can send to the output L&R RCA sockets. Audio section should be fine.

2. Signal meter shows the signal strength when a station is present.

3. Auto tuning unable to stop when a station is present (singal meter showing 90% scale).

4. Manual tuned at the station, but no audio output. Tried on different combination of wide/narrow, hi-blend .. etc).
5. Stereo light unable to turn on.
Appreciate somebody can help.

5. The antenna cable is tested good with a Pioneer tuner.

6. Voltage is checked, no sign of power supply problem.


Thanks and regards,
Norman

[DF96]

If the signal meter responds to a station but there is no audio and no stopping of a scan then the first area to look at is the FM discriminator. This may be within a chip, or it may be discrete circuitry with a couple of diodes and a special IFT.

PS this ought to be in the Analogue Source section - click on the warning triangle and ask the mods to move it

[bx19]

The discriminator is on CXA1064. No idea which signal is used to stop the auto tuning and when will the PLL starts to lock the station.

Best regards,
Norman

[Mooly]

Moved to Analogue Source