[sci.electronics] Crackling noise on T.V.

tedpan@techbook.com (Teddy Panarto) (06/13/91)

I have an old Sony TV with an annoying problem:
       Whenever the TV is displaying bright pictures (white color), the
audio gets distorted, and the level of distortion is proportional with the
amount of white colors on the picture. The problem appears easily on
Volkswagen commercial (if you've seen it), because most of the picture
color (i.e. background) is white.
Please e-mail (if this has been discussed before), or post any suggestions
or comments.
Thank you.

-- 
tedpan@techbook.COM  ...!{tektronix!nosun,uunet}techbook!tedpan
I'm not an employee here at TECHbooks, just a humble customer.

rcarter@wpi.WPI.EDU (Randolph Carter (nee. Joseph H. Allen)) (06/13/91)

The ghost of tedpan@techbook.com (Teddy Panarto) writes:
>I have an old Sony TV with an annoying problem:
>       Whenever the TV is displaying bright pictures (white color), the
>audio gets distorted, and the level of distortion is proportional with the
>amount of white colors on the picture. The problem appears easily on
>Volkswagen commercial (if you've seen it), because most of the picture
>color (i.e. background) is white.
>Please e-mail (if this has been discussed before), or post any suggestions
>or comments.
>Thank you.

If the distortion is in the form of an annoying hum, the problem might be that
the audio trap transformer is misadjusted.  This transformer acts as a filter
to remove the audio from the video before it goes to the video amplifier and
as a transformer to extract the FM from the video to bring it to the FM IF
section.

You should be able to find this transformer easily as it's right after the
video detector (diode) and before the video amplifier and also leads to the
audio section.

There might be more tunable components involved with this as well.  Try to get
the schematic.
-- 
/*  rcarter@wpi.wpi.edu */      /* Amazing */             /* Joseph H. Allen */
int a[1817];main(z,p,q,r){for(p=80;q+p-80;p-=2*a[p])for(z=9;z--;)q=3&(r=time(0)
+r*57)/7,q=q?q-1?q-2?1-p%79?-1:0:p%79-77?1:0:p<1659?79:0:p>158?-79:0,q?!a[p+q*2
]?a[p+=a[p+=q]=q]=q:0:0;for(;q++-1817;)printf(q%79?"%c":"%c\n"," #"[!a[q-1]]);}

lester@infonode.ingr.com (Lester Bartel) (06/13/91)

tedpan@techbook.com (Teddy Panarto) writes:

>I have an old Sony TV with an annoying problem:
>       Whenever the TV is displaying bright pictures (white color), the
>audio gets distorted, and the level of distortion is proportional with the
>amount of white colors on the picture. The problem appears easily on
>Volkswagen commercial (if you've seen it), because most of the picture
>color (i.e. background) is white.
>Please e-mail (if this has been discussed before), or post any suggestions
>or comments.
>Thank you.

>-- 
>tedpan@techbook.COM  ...!{tektronix!nosun,uunet}techbook!tedpan
>I'm not an employee here at TECHbooks, just a humble customer.

The same thing happens on my newer (4 year old) Magnavox 19" color set.
It only happens when credits are rolling or text is overlayed on the
picture.
-- 
Lester Bartel			b23b!naomi!lester@ingr.com
Dazix, An Intergraph Company	uunet!ingr.com!b23b!naomi!lester