Comments on: Both Speakers Found Open In ONIDA CRT TV

By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 13:11:19 +0000

In reply to Humberto.

Many thanks!

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By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 13:11:03 +0000

Many thanks for your detailed technical advice. I have carried out the modification as advised by my techie friends, who do it out of their true experience. Yes, I do agree that there will be some change in the frequencies. But that is better than failure of the speakers often. According to my friends, this solved such problems. So, I just followed it!

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By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 13:05:37 +0000

In reply to Yogesh Panchal.

Many thanks!

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By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 13:05:12 +0000

In reply to babums.

The output is protected in case of a voltage surge. This is a suggestion given by my expert technician friends. Many thanks for your comments!

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By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 13:03:56 +0000

In reply to Albert van Bemmelen.

My cleaning the outside of the CRT rear is not that hard to remove the coating! It only just cleans the dust formed. Nothing else is damaged. You concern is genuine! Many thanks for your comments and support!

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By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 13:01:38 +0000

In reply to Waleed Rishmawi.

Many thanks dear friend! Yes, it was worth.

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By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 13:00:41 +0000

In reply to Tyrone Arendse.

One end to IC and another to speaker. The other end of the speaker is connected to the IC. No need to bother about polarity as both are coming separately and one side is not grounded like in other circuits. But I connected the + to IC and minus to Speaker.

Many thanks for your comments!

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By: Parasuraman S

Parasuraman S — Fri, 27 Nov 2020 12:58:45 +0000

In reply to Mathew Charles karonga.

I recover the cost of spares and depending on the work, I charge the customer and my customers do pay me without raising an eyebrow!

Many thanks for your comments!

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By: Humberto

Humberto — Sun, 22 Nov 2020 03:01:44 +0000

Another more CRT TV to your collection and satisfaction bag.

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By: Henrique J. G. Ulbrich

Henrique J. G. Ulbrich — Sat, 21 Nov 2020 18:10:04 +0000

Another successful repair. Greetings! My comment this time is due to the capacitors inserted in the loudspeaker connections, a wrong decision in my opinion. I see three problems on it. First, it´s a bridge amplifier (TDA 7297), which means that this inserted capacitor will work directly with alternating current, not a variable DC current, as found in other types of amplifiers. Obviously, it is not an ideal regime for electrolytic capacitors, that will work out of their normals. The second issue is related to the work philosophy of a bridge amplifier itself. Such type of amplifier has intrinsic resources to keep the same DC voltage at the loudspeaker terminals, which impedes the loudspeakers to receive DC (the only variations observed are those of the signal being amplified). This DC stability is obtained by keeping the four non-inverted inputs at the same potential (internal point Vref of the IC) - see its data sheet at https://www.st.com/resource/en/datasheet/tda7297.pdf. If DC is found imposed to the loudspeakers terminals, by sure it is an IC problem, which shall be replaced. A third comment is related to the natural absence of the capacitor at the output of bridge amplifiers. They are not necessary in good quality (and stable) bridge amplifiers, with the advantage in this case that the response to low frequency (bass response) is optimized at the maximum.

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