Horus X12S No Sound from Speakers but ok on headset

[Nige8021]

I bought a used X12S and there is no sound output from the speakers, the headset jack works ok, I replaced the speakers that did not cure the problem so I replaced the LCD-GPS circuit board thinking it might be the headset jack not switching the audio but that did not fix it, I have tried re-flashing the OpenTx 2.3.15 firmware and tried EdgeTx 2.12.0 firmware and still nothing The speaker icon on the LCD is showing as 100%
I put my oscilloscope probe onto the contacts of the headset jack and activated a switch to get an audio output and there was no sign of the audio waveform on any of the connections, but when I plugged a headset in I could see the audio waveform on two of the connections.
I contacted FrSky customer service and they advised to check the RTC battery voltage as if it was around 3.3v it could cause problems ? the battery voltage with the battery installed was 3.06v and removed 3.09v Is there any other fault finding that I could try ?

 

[alm_nl]

And the wires to the speaker are ok, so if you measure continuity on those wires they are ok?

 

[Nige8021]

And the wires to the speaker are ok, so if you measure continuity on those wires they are ok?

I have tried two brand new speakers and I still get no sound from them, the new speakers measured at 8 ohms across the JST connector and the original speakers are also 8 ohms, plus when I put an audio frequency generator across the JST connectors I can hear the output, so it's not a faulty speaker

 

[alexiaamber]

And the wires to the speaker are ok, so if you measure continuity on those wires they are ok?

Since the headphones work and you only see the waveform after plugging a headset in, it really sounds like the jack detect/switching circuit is stuck in “headphones inserted” mode. Even replacing the LCD-GPS board may not help if the issue is further upstream on the main board audio amp section. You could try carefully checking the jack detect pin with a multimeter and also inspect for cracked solder joints around the audio IC area, especially on a used radio.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 1000 games

 

[Nige8021]

Since the headphones work and you only see the waveform after plugging a headset in, it really sounds like the jack detect/switching circuit is stuck in “headphones inserted” mode. Even replacing the LCD-GPS board may not help if the issue is further upstream on the main board audio amp section. You could try carefully checking the jack detect pin with a multimeter and also inspect for cracked solder joints around the audio IC area, especially on a used radio.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 1000 games

I have removed the main PCB and there are no broken tracks from the audio chip (APA2603A) and looking at the spec sheet for the audio chip

You can see that the signal for the headset being connected must be working as it should as I get no audio waveform on the headset socket when there is no headset connected'and the SE/BTL line on pin 9 does change state when a headset is connected, I have checked the two output signals from the chip going to the speakers and there is no output from pins 24/22 or 17/19, the output from the chip goes via an inductor then direct to the connectors for the speakers, so it's looking like the chip has failed I don't think my soldering skills are up to replacing it so I think I'm left with a couple of options, live with having no speakers, find someone to replace the chip or buy a new PCB if I can find one ?

 

[alm_nl]

I'd first check the 1uF capacitors if they are not shorted to ground and if the 36uH inductors measure continues with an ohm-meter. Also check if OUTP and OUTN pins are not shorted to ground. And, does the SE/_BTL signal do what is expected?

Does visual inspection show anything out of the ordinary, so no blown or discoloured components?

Maybe show a photo of the area of the board?

 

[Nige8021]

I'd first check the 1uF capacitors if they are not shorted to ground and if the 36uH inductors measure continues with an ohm-meter. Also check if OUTP and OUTN pins are not shorted to ground. And, does the SE/_BTL signal do what is expected?

Does visual inspection show anything out of the ordinary, so no blown or discoloured components?

Maybe show a photo of the area of the board?

The inductors on pins 24/22/19&17 are all showing continuity, I could'nt measure the values as I lent my LCR test meter to a fellow radio ham just before the covid lockdown in 2020 and I forgot he'd still got it ! the capacitors are not shorted to ground but as with the inductors I couldn't check the values of them, the 4 speaker outputs from the chip are not shorted to ground and the SE/BTL line is switching the outputs for the headset socket as it should.
Looking at the pictures below you'll see that no components look to be damaged

 

[alm_nl]

Does the volume control (pin7) work when the headphone is plugged in? And, do you measure the same voltage-range on pin 7 when not plugging in the headphone?

If none of the capacitors have a short, then replacing the chip might be a viable option.

Are there components or anything on the backside of the board where the APA2603A chip is? If there are no components on the backside where the APA2603A chip is, the best option might be to heat from the bottom (where the APA2603A chip is) with an hot-air soldering station to desolder it. A good electronics repair shop should be able to do that if you cannot do it yourself or have noone experienced to do it. I recommend to ask for a quote beforehand, to prevent unexpected surprises. Since there are a lot of small components in the nearby area it can be a bit tricky, but certainly not impossible. Heating from the top is more risky and might damage the speaker connectors.
Once the chip is removed, carefully clean the pads and apply fresh solder and electronics flux, place the chip and then apply heat from the bottom and reflow the solder.

 

[Nige8021]

Does the volume control (pin7) work when the headphone is plugged in? And, do you measure the same voltage-range on pin 7 when not plugging in the headphone?

If none of the capacitors have a short, then replacing the chip might be a viable option.

Are there components or anything on the backside of the board where the APA2603A chip is? If there are no components on the backside where the APA2603A chip is, the best option might be to heat from the bottom (where the APA2603A chip is) with an hot-air soldering station to desolder it. A good electronics repair shop should be able to do that if you cannot do it yourself or have noone experienced to do it. I recommend to ask for a quote beforehand, to prevent unexpected surprises. Since there are a lot of small components in the nearby area it can be a bit tricky, but certainly not impossible. Heating from the top is more risky and might damage the speaker connectors.
Once the chip is removed, carefully clean the pads and apply fresh solder and electronics flux, place the chip and then apply heat from the bottom and reflow the solder.

I've still got the PCB removed from the body so I can't check the volume pin, I retreived my LCR test meter and the inductors all measured around 18uH and the capacitors 20uF so not the values shown on the chip data sheet but i'm guessing that was just a guideline figure and FrSky decided on different values ?

I have ordered some replacement APA2603A they are just leaving China today as that was the only place I could find them, £4.30 ($5.80) for 5 chips A guy in my amateur radio club is going to replace the chip for me so I'll report back when the chips arrive