Saturday, September 9, 2017

LG 21 INCH CRT TELEVISION (MODEL 21SA1RG-T4) PICTURE OK BUT NO AUDIO NOW REPAIRED

I got a phone call from a customer who wanted his television checked and the complaint was picture is okay but no audio.

I requested him to bring it to the shop for checking and indeed he brought it up, i applied the power to confirm what he said about the tv initial symptoms and yes he was correct and therefore confirmed the television has audio problem.




I opened the set and went straight to the audio circuit and after scanning around the circuit for any suspect component, I found non.

Now it is time to use my ESR meter to check capacitors around this circuit and again I never got any capacitor which was suspect.


The next step is to check the two speakers which were rated 10 Watts and 8 ohm impedance and therefore with my digital meter set to diode range I tested across the speaker connector and got open circuit.


I continued increasing the range until I got open even on 10 Mega Ohm range and I concluded the speaker was open.

I moved to the other speaker and the reading were the same” open circuit”
With that I decided to find out if the Audio i.c was working or not, to do this I have to do some preliminary tests and the most important to start with is to find out if the i.c is getting stable and correct voltages.

To help me with the expected voltages I had to google this model which I got easily and here is the circuit diagram of IC LA42102L here below.



All the voltages were within range and this lead me to conclude the I.C was suspect, also touching the i.c I found it was cold which strengthened my case of suspecting it.

I went to the shop and bought a new one and after replacement I tested with a small speaker around my workshop attached to the previous speaker connectors and this time  got audio and I was a happy man.

Before going into celebrating mode I remembered I have no speaker of the type used in this television and also they are not in the market.

To take care of this I decided to salvage one from a JVC television junk lying around and did a replacement and the audio was good and clean.


Thank you guys

See you in the next class



10 comments:

  1. Replies
    1. Thanks and welcome my friend.

      Regards Humphrey

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  2. I always enjoy your approach to troubleshooting. Thank You for Sharing!

    ReplyDelete
    Replies
    1. Thank you Morakinyo for your feedback. Appreciated.

      Regards Humphrey

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  3. Hi sir please help me with my crt tv nippon japan no video only. 32 volts is presesnt on tuner and we also replaced tuner and memory 24c08 but still no reception. Tnx and god bless.don

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    Replies
    1. Check the RGB circuit at the CRT neck board, Seems like you are guessing what to change or not..i strongly advice you to invest in my eBook on CRT tv Repair course and don't forget to thank me later.

      Regards Humphrey

      Regards

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  4. First thanks again sir humphrey for sharing your repair articles regularly.I have a question on your method of diagnosing the trouble on that tv with no audio.when ypu check the speaker with your digital meter you set it in diode mode why can you not use in ohm setting?One more question sir, when you test the board by using the series bulb connecting to the B+ line is it possible to disconnect all wires leading to the picture tube so with the flyback disconnected to the picture tube as well.Because I read some of your previous articles that when you are in the costumer's house you bring home the board only to test it at home with the series bulb method leaving the picture tube and the TV casing. hope to have your reply soon.

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  5. Hi Romeo, 1.You can also use low ohm range to test the speaker impedance without any problem. 2.When you attach the bulb at the B+ line is called the Load, you are basically disconnecting the horizontal circuit supply and hence shutting it down completely and therefore all the other supplies like focus,screen and HV are not energized and therefore in-active and it is as if there are actually dis-connected from the tube.
    Regards Humphrey

    ReplyDelete