Muffled TV audio - Philips TDA9380 IC

[jamie powell]

Hi,
I have a Roadstar 10" CRT TV, PAL/SECAM model CTV1030.
The TV has muffled sound when watching broadcast TV signals (analogue) using
its antenna input, but when an AV source is connected to its SCART input,
the sound is fine.

The set's main IC chip is a Philips TDA9380PS/N2/3I. I'm not an electronics
expert, but I found a datasheet for this range of chips online
( http://www.datasheetcatalog.com/datasheets_pdf/T/D/A/9/TDA938X.shtml )
which, afaict, says that FM audio demodulation and de-emphasis takes place
within the chip itself.

I connected the chip's audio output pin directly to an external
amplifier-speaker, and the muffled effect was still present, possibly
suggesting that something within the chip itself is causing the issue, and
not some form of external low-pass audio filtering on the chassis.

Could anyone with experience with this IC chip suggest what the cause of the
problem might be?

Thanks,
Jamie.

 

[jamie powell]

On Wed, 15 Jul 2009 20:10:24 +0100, "jamie powell"

Unless the chip needs an external component or two for sound
processing then you've found the problem.

You think it's a faulty chip?
I know of another person with the same model TV who has the same issue, so I
figured it was either some kind of chip configuration problem, or a design
fault on the TV's PCB.

It could be a design flaw with the chip, but given that it's made by
Philips, and was apparently used in a lot of "economy" model TVs of various
brands, I'd be surprised if such a major flaw had gotten past
testing/quality control and into mass production unnoticed.

 

[jamie powell]

On Thu, 16 Jul 2009 00:26:36 +0100, "jamie powell"

You didn't mention the other person with the same model/same problem.

If you're not happy with it sell it and purchase something else.

With all due respect, this is an electronics repair group.
If you can't offer relevant and helpful advice to people with queries on
electronics repair, then don't post.

 

[jamie powell]

Could be designed like that for a nice 'mellow' sound. And reducing
intercarrier etc buzz from a cheap design.

Most unlikely, and it doesn't make anything sound "mellow" - one can barely
hear what people are saying. And low-pass audio filtering wouldn't reduce
intercarrier buzz in any event.

 

[jamie powell]

Turn it up then.

Doesn't help - makes it worse actually.

Bollocks.

Duh... buzz is low frequency innit. idiot.

 

[jamie powell]

What would you estimate the usable frequency response as heard at the
speaker at?

I tested the line output on a spectrum analyser. It rolls of after about
7khz, but the higher frequency content is still there, just much quiter than
it should be.

No - that's hum. Buzz is wideband. Have you never heard intercarrier buzz?

Of course I have. The vast majority of it is below 7khz, and there isn't any
on this set anyway.
You obviously don't know how to answer my question so kindly stfu.

I mourn the day when usenet was abandoned by academics and taken over by
conceited amateurs.

 

[jamie powell]

You don't need anything like 7kHz for clear speech. If you did, telephones
would be no use. AM radio in the UK is 4.5 kHz band limited.

Both of those have a lower bass response to match. This set has a very
uneven sound by comparison.

Why are you posting then? A pro would have no problem in sorting out the
cause, you conceited little shit.

I'm posting to ask for advice.
I'm not pretending to be competent in this area and wasting other people's
time as a result, unlike some people.

 

[jamie powell]

Telephone spec is 300 - 3000 Hz.

But make up your mind. You were complaining about 'muffled' sound. Do you
understand the common meaning of this, sound wise?



Then you could keep your posts to the point.

You can't help with my question and are completely without clue, although
loathe to admit it.
All you've done is waste my time and, less importantly, yours.

 

[jamie powell]

Tell you what, I more than likely, was doing warranty repairs for
major manufactures while you were still in diapers

Suuure you were....

 

[Bob Larter]

You can't help with my question and are completely without clue, although
loathe to admit it.
All you've done is waste my time and, less importantly, yours.

Gee, you're a real charmer.