Curtis 3227A no Audio Issues

[mike123333]

Hello, I acquired a Curtis 3227A LCD that has video and no audio. I ran through the basic voltage testing and capacitor evaluation with my ESR meter and did not find anything obvious. I was wondering what could be the issue with this type of symptom? I will have photos of the main board and power supply when the server is not as busy..

Thanks Mike

[mike123333]

Re: Curtis 3227A no Audio Issues

Here are the photos..

[CapLeaker]

Re: Curtis 3227A no Audio Issues

Audio ic bad? Something stuck inside the headphone jack?

[mike123333]

Re: Curtis 3227A no Audio Issues

Hello Capleaker - Thanks for the response, is that what typically goes bad with the audio portion of the board is the ic? how does one go about checking if it is bad or not?

[dick_barton]

Re: Curtis 3227A no Audio Issues

What are U10 & U21.
As CapLeaker suggests there may be a problem with the headphone socket otherwise you may not have the correct voltage supply for the Audio Amplifier.

[mike123333]

Re: Curtis 3227A no Audio Issues

Hello, when you say what are U10 and U21, are you referring that these IC's are possibly the problem child?

[Diah]

Re: Curtis 3227A no Audio Issues

did you take look at menu Audio setting if the sound out put set on intern speaker?

[martino]

Re: Curtis 3227A no Audio Issues

I would first check in the menu,to see if tv speakers are disabled?
Then try and see if you get sound out of the headphone jack.
U17 and U18 look like voltage regulators,guessing U17 regulates the power for U21 which is your audio driver IC.
You can find specs on U17/18 and see if they are correct in voltage output.

BTW,what happened to Ca16,it looks like it got messed with.

[budm]

Re: Curtis 3227A no Audio Issues

Do you get sound at the RCA AUDIO LINE OUT?
As MATINO indicated, check the setting also.

[dick_barton]

Re: Curtis 3227A no Audio Issues

Hello, when you say what are U10 and U21, are you referring that these IC's are possibly the problem child?

What part number is printed on each

[mike123333]

Re: Curtis 3227A no Audio Issues

I did look for the obvious as to whether the internal speakers were on or off, everything was good from there. There is no head phone jack so I cannot test that. I am presently using the rca audio jack to run from a dvd player.

As for the IC chips U16 and U17 ( that is the correct number on the boards) one is a 7808 and the other is 7805 , 7808 is outputting an 8 volt and the 7805 is at 5 v so both of them are good.

CA16 I had to take it out to test it offline with my ESR meter and had difficulties putting it back into the holes so I soldered it from the top.

As for U10 the number on IC is MSB1501-LF, A7MFR39C and U21 is TPA3124D2, O4TGA

[budm]

Re: Curtis 3227A no Audio Issues

The TV has RCA Red and White audio outputs, did you try that? If you get the sound there then that will partially eliminate problem in the pre-amp section.

[dick_barton]

Re: Curtis 3227A no Audio Issues

What is the supply voltage on Pins 1, 3, 10, 12, 19 & 20 on the TPA3124D2 audio amplifier.

[mike123333]

Re: Curtis 3227A no Audio Issues

Hi Budm, yes I did try that and nothing happens.

[mike123333]

Re: Curtis 3227A no Audio Issues

What is the supply voltage on Pins 1, 3, 10, 12, 19 & 20 on the TPA3124D2 audio amplifier.

All the voltages are reading 23.55 VDC

[budm]

Re: Curtis 3227A no Audio Issues

Since you are NOT getting any audio at the pre-amplify RCA line out which the circuit is BEFORE the power amplifier section then the problem cannot be in the power amp section.

[mike123333]

Re: Curtis 3227A no Audio Issues

Since you are NOT getting any audio at the pre-amplify RCA line out which the circuit is BEFORE the power amplifier section then the problem cannot be in the power amp section.

I was do more troubleshooting and have a question, if you can see in the picture the 2 large capacitors next to the speaker plugs. when I check the voltage from ground to the speaker plugs I get 12-13V, even if I check across the neg and pos leads of the plugs. If I check the capacitors from ground to + of capacitor I get the same voltage, however if I check the voltage across the capacitor leads it is ~0.7V. If I check the resistance of the ground to the neg lead of the caps I do not get continuity, does this sound correct?or should there be a ground continuity to the neg side of the caps? hopefully you can follow what I am asking

[mike123333]

Re: Curtis 3227A no Audio Issues

forgot to mention, the voltage of the caps from gnd to either lead of the cap is measuring at 12-13V, so its not only the positive lead of the cap its also the neg

[budm]

Re: Curtis 3227A no Audio Issues

If you look at how the amplify is setup in the spec sheet of the IC, you will see that there is DC BLOCKING/COUPLING cap between the output pin of the IC and the positive pin of the speaker. So the DCV on one side of that coupling cap that is connected to the output pin should be = 1/2 of the VCC supplied to the IC, the other side of the cap that is connected to the speaker + wire should be 0VDC, you should check the DCV the two legs of the speaker (speaker has to be connected to the connector).

[mike123333]

Re: Curtis 3227A no Audio Issues

I checked the voltage across the speakers with them plugged into the circuit. The left side starts at 12v and steadily drops down I stopped at 5v monitoring. The right side started at 3.6 and pretty much stayed there. These were measured across the speaker plugs. Could this be due to the output side of the IC is faulty?

I don't quite understand your explaining on how the voltage is 1/2 from the DC blocking/coupling cap. I tried to follow it but don't quite understand. if you can elaborate on that. I would like to better understand. Thanks