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Chinese TV - Video OK, No sound, loud noise

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Menticol

Active Member
Hello!

The patient today is a SANKEY CMX4400 (Goldstar parts inside). I know, is a crappy chinese TV, but it belongs to a low-income family, they cannot afford a better one.

Video is OK, but audio is dead. There is a loud high pitched noise, coming from the PCB (not trough the speaker, speaker is dead)

Capacitors seems fine. I don't know where to start, because seems like its not related with the audio-stage.

Thank you very much!
 
The high pitched noise could be from a transformer but im not sure. i cant think of what else it could be. what part of the tv's circuits are making the noise e.g power supply, inverter board
 
You may be hearing the switching power supply squealing due to a change in it's parameters from a faulty audio output chip or associated component(s). Without a diagram it's difficult to troubleshoot from here. Troubleshooting experience would allow some of us to possibly repair it without a service diagram, but you have the set, and not me or the others here. If you are not experienced in television repair, put the cover back on and forget it... don't risk further damage to it or injury to yourself --- SERIOUSLY!
 
You may be hearing the switching power supply squealing due to a change in it's parameters from a faulty audio output chip or associated component(s). Without a diagram it's difficult to troubleshoot from here. Troubleshooting experience would allow some of us to possibly repair it without a service diagram, but you have the set, and not me or the others here. If you are not experienced in television repair, put the cover back on and forget it... don't risk further damage to it or injury to yourself --- SERIOUSLY!

Thank you very much by your concern Hitech, don't worry, I know how to properly discharge the CRT and the required safety guidelines.

I really doubt there is any diagram for that thing, so testing the individual components was the way to go.

As you said, the annoying sound came from the power supply. I've traced the audio circuit, and all the discrete components were OK. The last step would be replacing the audio chip, but there is a catholic commemoration on the country, everyone is on vacation and all the electronics stores are closed (absurd)

I gave up, and returned the set to the owners :(

PS: Desoldering that !"#$%@ IC would be great, to check if the sound goes away.
 
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I was introduced to Goldstar office telephone systems in 1980. The pcbs and soldering were horrible. They performed poorly. But they were very very cheap.
Now they are called LG and their products are much better.
 
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