- Sony ST-S211 Tuner Problem: Receiving Mono Only, Can't Switch to Stereo. Help Needed!

Hello,

I have a problem with the sony tuner, it only plays mono! STEREO cannot be switched on at any station. Do you know what's happening to him?

thanks
alexsunny

After forcing the stereo mode, what are the voltages on pin 10 of the LA1851 chip?
The CF21 456kHz ceramic resonator, connected to the 13th pin of the LA1851 chip, needs to be checked. Are there oscillations?
Even if you can see the oscillations there, the resonator could, for example, drift away too much from old age, from the expected 456kHz frequency and the decoder PLL loop is not able to correct it with the VCO generator at 456,000kHz (24 x 19kHz) to switch on the stereo.

Does the equipment have only this defect or does it have more, such as not stopping in automatic tuning?
If you only have the stereo defect, try adjusting the RV21 or in the last case replace the Ic LA1851N

Hello. I hope it will be read. I have a Sony radio with LA1851 and there is no sound at the output of this IC. The device has been tested and is healthy from the LA1851 output to the speakers. Only when changing the band from AM to FM, it makes a pop sound. Thankful

Specify the symbol of this Sony receiver. Just focusing on the LA1851 may be the wrong lead. It may turn out that the LA1851 chip is working and the preceding blocks have a fault. For example, the VHF head unit, or there is no signal coming from the VHF head unit to input pin 1. Hence the need for a schematic of the entire unit to be able to talk about diagnostics.
What is the voltage on the 17th leg of the LA1851? Does it change when switching AM/FM?
Is the receiver silent in the AM band too? Just the clatter itself from switching bands?
So I understand that there is also deafening silence on legs 14 and 15?

Remove the CFT 21 filter and check that it works

Remove the CFT 21 filter and see if it works.
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