[tvservice] Re: RCA ctc177bh2 no sound..

  • From: Sam Barnum <sbarnum@xxxxxxx>
  • To: tvservice@xxxxxxxxxxxxx
  • Date: Thu, 04 Nov 2004 20:53:47 -0500

Thanks for your replies.  I double checked to see if there is any sound 
from the speakers at any volume. But no there is none, they are dead 
silent at all times. I also double checked the speakers and wiring from 
the PCB to them. Good results for both.  I also pulled out the scope, 
and using my VCR as the source, I had a nice clean audio waveform on 
pins 1 and 5 of TDA7263(Audio AMP non-inverting inputs). The amplitude 
of that wave followed volume control up and down nicely. However MUTE 
had no effect and didn't even show up on the TV screen as is typical, or 
as the volume control had.  I also noted a 1.5v constant voltage on 
SUR/MUTING pin (#3).

So now I'm thinking either bad TDA7263, or mute is on permanently..

Any more thoughts?

Thanks, Sam

There is a mute signal from the main micro I think, that mutes the sound
when changing channels. I have found that bad. It is NOT the same mute
circuit as the one that is used when you push the mute button. There is a
resistor you can remove to disable it. I was told to do that by one of RCAs
$2/min. techs and then a year or two later they denied that they ever
recommended doing it. Some guys say that will destroy the speaker eventually
but I have not seen it happen.

Russ Hoyt
Hoyt's TV
Exeter, NH

----- Original Message -----
From: "Gilbert Kelley" <gjkelley@xxxxxxxxxxxx>
To: <tvservice@xxxxxxxxxxxxx>
Sent: Thursday, November 04, 2004 4:15 PM
Subject: [tvservice] Re: RCA ctc177bh2 no sound..

 > Content-Type: Text/Plain;
 >   charset="iso-8859-1"
 > Content-Transfer-Encoding: quoted-printable
 > First I would suspect the EEPROM.....Second I would recheck all my ground
 > connections around the tuner shield....If you turn the sound all the 
way =
 > up
 > do you get low audio?=0D
 > =0D
 > Hope this helps some....let me know what you find.=0D
 > =0D
 > Gilbert =0D
 > -------Original Message-------=0D
 >  =0D
 > From: Sam Barnum=0D
 > Date: 11/04/04 14:41:22=0D
 > To: tvservice@xxxxxxxxxxxxx=0D
 > Subject: [tvservice] RCA ctc177bh2 no sound..=0D
 >  =0D
 > Hi all,=0D
 >     I have an RCA CTC177BH2 with no sound, not even a click or hiss
 > the TV is turned on.  Video is good from both the tuner and video-in
 > sound out with audio-in from VCR either.  I had the TV to fix a cold=0D
 > solder joint under the RF shield.  While I had the soldering iron in 
 > hand I also reflowed a number of joints on the LA7610 (signal
 > and LA7765 (stereo processor), I didn't touch the TDA7263(Audio AMP).
 > don't know if the sound was working before hand.  However the I have=0D
 > confirmed that the speakers do work.   Any thought on where I should=0D
 > look first?=0D
 >  =0D
 > LA7610=0D
 > LA7765=0D
 > TDA7263=0D
 > Other??=0D
 >  =0D
 > Does anyone have a data sheet for the LA7610?=0D
 >  =0D
 > Thanks, Sam

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