[TechAssist] Re: [Fwd: RCA CTC169BG 35 inch. sound modulates the video]
- From: "Damon" <DAMON101@xxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 29 Jan 2002 20:47:35 -0500
Phil,
I know this is unlikely to occur and I doubt this is what you'll find.
However we had a Toshiba 35 inch TV with audio affecting the horizontal
lines, turns out the speaker wire was pinched underneath the crt's metal
mounting bracket. When we turned up the sound the pix would look like we had
erratic horiz sync.
Looking at schematics: Block diagram shows Video/Audio is common to pin 45
of U1001, passes thru Q2302 buffer which then splits the audio thru cf1201
4.5 mhz bpf to pin 51-u1001 input to fm detector which outputs to pin 57.
Video from q2302 goes thru cf2301 4.5 mhz trap filter to q2701 buffer. This
same video is used on big pix and pip pix, so you may want to see if pip pix
is also affected. BTW does it shift the horiz,. or does it brighten/darken
the video?
Let's see if there are common power supplies: Well....yes and no. Looks like
the major power supplies are a + and - 12 volt supply which is broken down
to 5 and 6 volts on the audio process (stand up board) board, your -12 volt
line comes from the ihvt and CR4705. Your +12 comes from Q4702 (12 v Run
switch). That's it for audio and about the only 2 supplies you need to check
for audio noise. The + 12 volt is the only true common power supply, maybe
you should check the pinched wire as a likely possibility.
Hope this helps.
Damon Brunger
damon101@xxxxxxxxxxxxxx
Telrad Electronic Services
Ft Wayne, IN 46815
----- Original Message -----
From: "Phil Bader" <philbad@xxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Tuesday, January 29, 2002 1:18 PM
Subject: [TechAssist] [Fwd: RCA CTC169BG 35 inch. sound modulates the video]
>
>
>
> -------- Original Message --------
> Subject: RCA CTC169BG 35 inch. sound modulates the video
> Date: Tue, 29 Jan 2002 13:17:20 -0500
> From: Phil Bader <philbad@xxxxxxxxxx>
> Organization: Jan Phyl TV Inc. Winter Haven, Fl. Est.1976.vioce/fax
> 863-299-8821
>
>
> At low volume levels the pix is very good.Turn up the sound and the
> picture modulates at the audio rate.I assume there may be a common
> video/audio voltage source that is sagging under load. Any
> histories?-Phil
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