sci.electronics.repair@googlegroups.com

Today's topics:

* HDTV has no sound - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/3a7aee93765769fb?hl=en
* Black and While programs on Color Tv - 2 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/4832decd7595bba7?hl=en
* Strangely marked BUZ Mosfet - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/aff797bedba2c908?hl=en

==============================================================================
TOPIC: HDTV has no sound
http://groups.google.com/group/sci.electronics.repair/t/3a7aee93765769fb?hl=en
==============================================================================

== 1 of 1 ==
Date: Wed, Apr 6 2011 11:26 pm
From: whit3rd

On Thursday, March 24, 2011 1:12:50 PM UTC-7, vjp...@at.BioStrategist.dot.dot.com wrote:
> [no sound on HDTV] . I am
> looking at this $80 TV that has worked for about 18 months and am trying to
> figure if it is worth fixing.

If it has stereo sound, one bad capacitor wouldn't take out both channels.
And, if there are audio inputs (like for a DVD input), you can try
an external sound source to see if the amplifiers and speakers are OK.

Firstly, you have to exercise the problem, see what part of the block
diagram the fault is in...

Second, you have to inspect the hardware and determine which components
are in which block. If there's a melted thingummy and you can see the crater
where it lost its smoke, things get easier.

Then, with about twenty minutes of work into the job, you think about 'worth'
issues.

==============================================================================
TOPIC: Black and While programs on Color Tv
http://groups.google.com/group/sci.electronics.repair/t/4832decd7595bba7?hl=en
==============================================================================

== 1 of 2 ==
Date: Wed, Apr 6 2011 11:45 pm
From: isw

In article <W7_mp.24268$5t2.417@newsfe06.ams2>,
"Ian Field" <gangprobing.alien@ntlworld.com> wrote:

> "isw" <isw@witzend.com> wrote in message
> news:isw-4E35A7.20165205042011@[216.168.3.50]...
> > In article <KFLmp.2976$9h6.2210@newsfe02.ams2>,
> > "Ian Field" <gangprobing.alien@ntlworld.com> wrote:
> >
> >> "William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
> >> news:infp1h$k9v$1@dont-email.me...
> >> >> Also an artifact of NTSC -- Never The Same Colour
> >> >
> >> > Not true. NTSC is neither inherently inaccurate or unstable.
> >>
> >>
> >> The UK PAL (Phase Alternate Line) inverts the subcarrier phase on
> >> alternate
> >> lines so phase distortion during transmission cancells itself out - NTSC
> >> doesn't and is inherently prone to drift, hence it was dubbed; Never
> >> Twice
> >> the Same Colour.
> >
> > But they traded color drift for high-brightness ficker; not necessarily
> > a good choice, since the early color drift of NTSC, being due to
> > equipment instabilities, was soon fixed by better gear, while PAL's
> > flicker problem, having been designed in, persisted.
>
>
> Flicker is due to the 50Hz field rate, its only noticeable if you're used to
> 60Hz field rate.

That's not what I was talking about.

PAL's high-brightness flicker problem is caused by a combination of it's
very low interlace rate and the human eye's sensitivity to periodic
variations in light intensity, especially at high levels of brightness.

The actual interlace rate (the rate at which a specific "pixel" repeats
with the exact same amplitude and phase) is, for NTSC, half the frame
rate -- say, a tad below 15 Hz. (Don't forget that the color subcarrier
is also interlaced). Due to it's extra phase alternation (the "P" of
"PAL"), the actual interlace rate for PAL is *one quarter* of its frame
rate, or 6.25 Hz.

NTSC's flicker rate is high enough that it's just not very noticeable,
while PAL's is well below the flicker fusion rate, and is easily
noticeable.

After a while, "high-end" PAL sets were offered which did not exhibit
the flicker problem, but (unlike NTSC's hue problem) it was not
eliminated so much as obscured by considerably more complex (and
expensive) signal processing.

Isaac

== 2 of 2 ==
Date: Wed, Apr 6 2011 11:53 pm
From: isw

In article
<9905863f-b7fd-4011-99b4-34614b2aa9e9@i14g2000yqe.googlegroups.com>,
stratus46@yahoo.com wrote:

> On Apr 5, 11:11�am, John Robertson <s...@flippers.com> wrote:
> > William Sommerwerck wrote:
> > >> How come some of the old B&W programs on the "Oldies Channel"
> > >> (THIS-TV) are black and white, while others are tinted, usually black
> > >> and greenish white? Yes, the color programs are accurately colored,
> > >> so it's not that the TV colors are off, and some B&W programs are
> > >> actually correct. Is this in the film or is the tv transmitter wrong?
> >
> > > Filmed B&W programs are often transferred with a color camera or telecine
> > > and transmitted as a color signal. The transfer equipment might not be
> > > set
> > > up correctly.
> >
> > > It's also possible your TV's tracking is off, but you say some B&W
> > > programs
> > > look okay, so that's not likely.
> >
> > > I occasionally watch this, and haven't noticed any unusual color casts in
> > > B&W shows ("Bat Masterson", "Sea Hunt", etc).
> >
> > > I've noticed something similar on Blu-rays, both color and B&W. Scenes
> > > appearing in the supplemental material have a different color balance or
> > > cast, even though they're presumably derived from the same source. "North
> > > by
> > > Northwest" and "Young Frankenstein" are good examples.
> >
> > Also an artifact of NTSC - Never The Same Colour -

I don't think so. For DVDs, "NTSC" or "PAL" does not exist (or, does not
*need* to exist), at any point in the signal chain prior to the final
video output portion of the DVD player, and whatever performance it has,
won't vary from one part of a disk to another.

The effect you speak of is most likely due to the fact that the
supplemental stuff just didn't get the same degree of attention when
color correcting the film sources.

Isaac

==============================================================================
TOPIC: Strangely marked BUZ Mosfet
http://groups.google.com/group/sci.electronics.repair/t/aff797bedba2c908?hl=en
==============================================================================

== 1 of 2 ==
Date: Thurs, Apr 7 2011 12:15 am
From: "Gareth Magennis"

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:904nfoFg8jU1@mid.individual.net...
>
> "Gareth Magennis"
>
>>
>> If there is any doubt what these oddly marked devices actually are I will
>> do just that.
>
>
> ** What does your PEAK say about the pin out and the Gate threshold
> voltage ?
>
> Should be Source on the case and about 0.5 to 1.0 volts.
>
>
> .... Phil
>

Doesn't display voltage information, it either says its a "* channel mosfet"
and identifies the pins, or "no valid part found". Its a PIC based device
I believe.

I bought it purely to check Mosfets go or no go, and it works well.

Gareth.

== 2 of 2 ==
Date: Thurs, Apr 7 2011 12:52 am
From: "N_Cook"

Gareth Magennis <sound.service@btconnect.com> wrote in message
news:p-SdnRAdzr627QHQnZ2dnUVZ8oydnZ2d@bt.com...
> Hi,
>
> I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906
> mosfets. All output devices have been resoldered or replaced at some
point,
> and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P.
>
> I've repaired a few of these in my time but never come across this
marking.
> Is it a Trace internal number, or have these been substituted in from
> elsewhere? Are they actually BUZ906?
>
> (One BUZ901 is blown, the other 3 check out OK on a PEAK component
tester).
>
>
> Cheers,
>
>
>
> Gareth.
>
>

perhaps obtained from these people
http://www.autogarduk.com/stock%20list%2027.htm
41 P and 274 N

What are the test parameters of a Peak?

==============================================================================

You received this message because you are subscribed to the Google Groups "sci.electronics.repair"
group.

To post to this group, visit http://groups.google.com/group/sci.electronics.repair?hl=en

To unsubscribe from this group, send email to sci.electronics.repair+unsubscribe@googlegroups.com

To change the way you get mail from this group, visit:
http://groups.google.com/group/sci.electronics.repair/subscribe?hl=en

To report abuse, send email explaining the problem to abuse@googlegroups.com

==============================================================================
Google Groups: http://groups.google.com/?hl=en