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Problem with Samsung TV

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Arnold Stewart

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Jun 27, 2001, 9:04:32 PM6/27/01

Samsung TV Model TXG248, Chassis KCT52B (manufactured March 1998)
TV came in with no control of the sound. It was full on. Pressing on the
volume down button (on TV or remote) caused the set to turn off. After
removing the cover and doing some checking, I no longer have any sound.
The sound output IC is a TDA7057AQ. It has input on pins 3 & 5, has
output on pins 8&10 and 11&13, but insufficient to drive the speakers.
Input supply voltage is at 13.2V (pin 4)
I would normally think the IC is at fault (I've checked the parts
surrounding it) but what gets me is that when pressing the volume up, or
down, the TV turns off for a few seconds then comes back on by itself.
Volume control voltage is at about 1 volt. I can't check to see if it
varies, the set turns off if I touch a volume button. I did try to apply
an external voltage. Nothing happened.
Any ideas? Thanks.

Arnold Stewart

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Jun 27, 2001, 9:08:04 PM6/27/01

Model number should read TXG2548

Nobody Special

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Jun 27, 2001, 10:56:57 PM6/27/01

Arnold Stewart <arnold....@sympatico.ca> wrote:

I'm not familiar with this model but here are some common things you
might check for:

1) Solder connections. Always a likely source of problems. Solder
around the microprocessor, the function buttons, audio IC's, etc.

2) Corroded function switches. (Sanyo TV's are especially good for
this.) If the function buttons are controlling a resistor matrix,
corrosion of the switch or resistors can make strange things happen.

3) Leaky bypass caps. The function lines out of the micro usually have
ceramic bypass caps, typically .01 or .001 ufd, to ground to keep RF
from causing troubles. These get leaky and keep the control lines from
running their proper values.

Good luck!

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Tom MacIntyre

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Jun 28, 2001, 5:22:22 AM6/28/01

EEPROM, uP, leaky zeners around the uP.

Tom

David Kuhajda

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Jun 27, 2001, 11:07:36 PM6/27/01

to Arnold Stewart

Seen symptom hundreds of times, blown eeprom. You will need service
manual to get the correct option codes and alignment info to complete
the repair however.

You need to make sure the crt dag grounds are good, and the crt does not
have an intermittent hv short or arcing. per Samdung bulletin. Samdung
bought a big pile of the old junk Zenith made crt's and put them in a
load of 25" size tv sets, hence the crt arcing problems and blown
eeproms.

David

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