Wednesday, April 4, 2018

14 Inch LG CRT television model 14CD1RBE screen picture washed out audio okay

I meet a client who wanted her TV checked by a technician and after asking her a few questions about the nature of the problem, I realized I was not getting the real picture of how the screen was since she was talking of picture being washed being out.

So I requested her to send me the screen shot of the TV screen via whatsup and this is what I got.

After getting the screen shot I now realized the TV actually has a problem and need to be checked.

In the beginning I thought maybe it was just a setting problem which I could have handed remotely.

So I passed by and picked it up, back to my workshop I opened the TV and I headed straight to the RGB circuit.

I decided to attack this problem by talking the voltage reading on this circuit and here I what I got and wrote I down on a piece of paper.

With the data collected now it is time to analyse it, in politics they say numbers don’t lie, this also hold true in electronics and therefore let us analyse each line at a time.

9Volt line reads 8.98 volts which is within the range, RGB bias 1.6 volts is within the range also.

Come to the RGB Amplifier voltage is 122Volts and here I have problem with this voltage since on the PCB board it was marked as 180Volts and therefore I will need to do more testing on this line.

Usually a drop in voltage on an outlet maybe caused by faulty capacitors and now it is time to pull out my ESR meter to test the capacitors on this line and luckily they are very few.

I started with the capacitor C540 rated 4.7uF/250V near the fly-back transformer and this is what I got.

A capacitor rated 4.7uf/250V should not have ESR reading of more than 10 ohms but here it is reading 0.15K ohms!

A little mathematics we get 0.15 K X 1000= 150 ohms, this is far too high ESR which is capable of bringing down even fighter jet without a single shot.

Also note that the Capacitance was 4.7uF but now it is reading 909.9 nF or 0.9 uF!

I replaced this capacitor with another of the same value and voltage which I found on a junk nearby and after testing it with my ESR meter and found it health I did the replacement.

I assembled the board hurriedly since I was sure I got the culprit and also time is a limited resource (we have only 24 hours a day, take away eight hours sleeping)

I applied the power and to my surprise the problem was still there but now the screen is not white but had some color as you below.

I Continued checking for any related component on that line and I was almost giving up when I noted a capacitor on the neck of CRT neck board which was also rated 4.7uF/250V and testing it I noted the ESR was also very high and by the time I removed it from the board one leg was already rotten and broke out, The capacitor was labelled C901 (4.7uF/250V)

I also replaced this capacitor and after applying the power with my eyes fixed on the screen I was happy with the results.

Kindly noted that the two capacitor has no sign of stress or top swollen and therefore a tech without an ESR meter will not have it ‘as business as usually’ and he or she might even fail to do this simple repair.

Thank you friends
Stay safe

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