sci.electronics.repair@googlegroups.com

Today's topics:

* Good sound; intermittent picture. - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/45ba5bddf76a0064?hl=en
* Any TV experts here? Maybe an aerial specialist too. - 4 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/ad793e4d0dda11c6?hl=en
* Whirlpool WAOT11M00 11 Fins Price In India - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/eab6bb74321affae?hl=en
* Toshiba D-R160 DVD recorder, 2009 - 2 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/5ef69f3de1c23bd1?hl=en
* how hot should a schottky get? - 5 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/c666fc4f127ae347?hl=en

==============================================================================
TOPIC: Good sound; intermittent picture.
http://groups.google.com/group/sci.electronics.repair/t/45ba5bddf76a0064?hl=en
==============================================================================

== 1 of 3 ==
Date: Wed, Nov 2 2011 9:54 pm
From: micky

On Wed, 2 Nov 2011 11:39:23 -0700 (PDT), "malua mada!"
<fritzo2ster@gmail.com> wrote:

>
>> I have a 25" Sharp TV, CRT, that often loses its picture, but never
>> the sound.   (Other than that, the picture and sound are very good.
>> It's analog and I only use channel 3 and a separate tuner.)
>>
>TV tuner?

DVDR with tuner and hard drive. In the bedroom.

>So is that tuner putting out TV signal on channel 3?

Yes, that's it. .

>Or is it putting
>out separate audio and video (more likely)?

No. I think it has audio and video outputs on the back of it, but
when I put in the wiring for the other rooms, I didn't think to put in
more than one co-ax line. But it's working fine in the kitchen.
Only this tv in the basement is intermittent. .

> Is there more than one
>connection between the two?
>Audio tuner and separate audio sound system?

No. Everything is on that one co-ax line.

Thanks.

== 2 of 3 ==
Date: Thurs, Nov 3 2011 10:53 am
From: PlainBill@yawhoo.com

On Tue, 01 Nov 2011 02:54:51 -0400, micky <NONONOmisc07@bigfoot.com>
wrote:

>Can a tv input signal connection at the input coax connector affect
>only the picture and not the sound??
>
>
>I have a 25" Sharp TV, CRT, that often loses its picture, but never
>the sound. (Other than that, the picture and sound are very good.
>It's analog and I only use channel 3 and a separate tuner.)
>
>The picture can be restored by bending the co-ax TV input cable one
>way or the other. Sometimes this lasts for days at a couple hours
>each day. Other times it lasts for 10 seconds. I have a string
>attached to the cable. Usually pulling the string, pulling it
>tighter, or letting the string go makes the picture come back. I wrap
>the string around a drawer knob on my workbench (beyond which is the
>tv)., sort of like roping a calf and tying the lasso to the saddle
>pommel. This is the closest I've gotten to being a cowboy.
>
>Is it possible that the problem is the co-ax input cable connector or
>some part or connection near to that???? I don't see how a bad
>connection that early on can interrupt the picture and have no effect
>on the sound.
>
>Or is it just a locational coincidence, and the problem has to be
>somewhere in the main circuity, after the sound and picture are
>separate????
>
>Or in the high voltage? although I would think if it were the high
>voltage, I would see the picture start out small, maybe as a pinpoint,
>and enlarge when I pulled on the string and restored the picture.
>Instead it just appears on the entire screen at once.
>
>Thanks for any help you can give.
If I recall correctly, as the modulation gets stronger, the picture
gets darker. Of course the tuner/IF system had AGC, which will try to
maintain an adequate signal output as the strength of the input signal
changes. And some sets were designed to blank the screen (or put up a
blue screen) if the input signal was below adequate levels. However,
I can't see any reason to believe that that is happening in this case.

By far, the most likely situation is that there is a bad solder joint
in the video processing area AFTER the audio subcarrier is extracted.
Given the level of integration in modern TVs, the tuner and IF strip
could be integrated into a single mackage. As such, it is unlikely
that replacing the RF input would fix anything.

By the deacription, it's unlikely it's the high voltage.

There are a number of sources for schematics and even complete service
manuals online. One of the better ones is Elektrotanya.com.

PlainBill

== 3 of 3 ==
Date: Thurs, Nov 3 2011 5:26 pm
From: Sylvia Else

On 3/11/2011 3:49 PM, micky wrote:
> On Tue, 01 Nov 2011 18:59:27 +1100, Sylvia Else
> <sylvia@not.here.invalid> wrote:
>
>> On 1/11/2011 5:54 PM, micky wrote:
>>> Can a tv input signal connection at the input coax connector affect
>>> only the picture and not the sound??
>>>
>>>
>>> I have a 25" Sharp TV, CRT, that often loses its picture, but never
>>> the sound. (Other than that, the picture and sound are very good.
>>> It's analog and I only use channel 3 and a separate tuner.)
>>
>> If by "loses its picture" you mean that the picture abruptly and
>> completely dissappears, with no effect at all on the sound, I'd say "no".
>
> Boy, am I stupid. Ifnore my first answer. I thought you described
> the problem here. I thought that was the problem when I first posted.
>
> But in reality, maybe the picture is still there. It's just so dark
> often nothing can be seen but little blue and red hyphen-shapped
> lights blinking on for an est. 20th of a second, and then bliniking
> on somewhere else around the screen. Hundreds of them at any one time.
>
> At the same time, when closed captioning is on, it looks perfect,
> white and bright and the letters fully formed.
>

You said the previous owner of the television was seeing the same
behaviour. Did he also have what is now your DVDR unit connected?

It's not clear what role the DVDR unit is playing here. If it's tuning
an analogue channel, and just frequency shifting it, then the closed
captioning would have to be generated by the TV. In that case, there is
clearly a fault somewhere in the between the TV's own tuner, and where
the closed captioning gets superimposed on the picture.

On the other hand, if the DVDR unit is tuning a digital channel, and
providing an analogue output, complete with closed captioning, then it's
hard to see that there can be anything wrong with the TV at all, with
the problem lying in the DVDR unit, which is, after all, connected to
the other end of the coax that you waggle.

> Not tonight, but I recall that sometimes the picture can almost be
> seen, like it is night time, with most of it black and maybe part,
> maybe the background, very very dark blue or very very dark red,
> barely one shade lighter than black. I guess when the real color
> isn't blue or red, it just looks like black.

That really sounds to me as if the DVDR unit is just frequency shifting
an analogue channel, and that there's a faulty connection or dry joint
in the video signal path in the TV - a small amount of the signal gets
through by the capacitance of the failed connection.

Sylvia.

==============================================================================
TOPIC: Any TV experts here? Maybe an aerial specialist too.
http://groups.google.com/group/sci.electronics.repair/t/ad793e4d0dda11c6?hl=en
==============================================================================

== 1 of 4 ==
Date: Thurs, Nov 3 2011 12:59 am
From: ~BD~ <~BD~@nomail.afraid.org>

Arfa Daily wrote:
> <snip>
>
>>> Arfa
>>
>> I really appreciate your comprehensive comments, Arfa. Thank you. :-)
>>
>> FYI, here's a piccie of the antenna: http://i44.tinypic.com/oumsch.jpg
>>
>> My eyes were playing tricks on me - it's a round section bar and 9,
>> not 8, X's!
>>
>> I did speak to Sony's help line (a girl in Cairo, Egypt!!!). Her view
>> was that it is definitely *not* a TV problem, but one of signal strength.
>>
>> Many thanks for your warning about cowboys and rip-off merchants. I'll
>> be careful to select wisely if/when I need professional help.
>>
>> Cheers!
>>
>> Dave
>>
>
> Looking at the picture, I think that you can be 90% sure that what you
> have is a narrow bandwidth antenna from the analogue days. It may or may
> not ultimately prove satisfactory for digital. If you remember back to
> the early days of the 'digital TV revolution' with the TV ads featuring
> Johnny Vegas and Monkey, the basic message was that you could just glue
> your shiny new digital TV or STB to your existing antenna, and
> immediately enjoy all of the benefits of the digital system. Well, yes
> and no. As far as I know, it was always the intention that when
> everything was finally settled, the multiplexes for each TV region,
> would largely match the blocks of band originally used for analogue TV
> in those areas - hence an existing antenna should work ok. However, it
> never really worked out that way in the interim. To avoid interference
> problems to and from existing analogue services, whilst these were
> phased out over whatever time period it was - around three years I think
> it's been - multiplexes belonging to a geographical area, were shoved
> all over the whole UHF band, which is about 400 MHz wide. So you could
> easily finish up with one multiplex at the bottom of the band, and
> another for your area, right at the top. That's the way it was where I
> am. Also, whilst best efforts were made to co-locate digital
> transmitters on the same sites as the existing analogue ones, that
> didn't always work out either, so you could finish up with the analogue
> service, and the digital service broadly in the same direction, but
> possibly several degrees apart. If you have a highly directional
> existing analogue antenna, that could make it quite a bit 'off-beam' for
> the digital service. On top of all of this, they have had to adjust
> transmitter powers up and down as well, because of mutual interference
> problems, and multiplex contents have also been shuffled around. It is
> only in the last few months, as the analogue transmitters have gasped
> their last, that there has finally been some efforts to stabilize the
> whole situation, with finalised transmitter powers and multiplex
> locations within the band. There has also been some shenanigans
> regarding what parts of the UHF band are left available for TV use,
> after revised chunks are sold off to the cell-phone operators. This has
> caused some problems with space that the broadcasters thought was
> already allocated to allow broadcast of HD within the Freeview
> terrestrial service, and has resulted in a rethink as to how this is now
> being accomplished.

Thank you for sharing your knowledge with me, Arfa - I am certainly a
much wiser man now. It's obviously a very complicated business but you
seem to know your stuff!

> All in all, if you can live with the current situation for a little
> while longer, you might find that it all settles down enough to give you
> perfectly acceptable results, using that antenna. Of course, the exact
> reverse might also turn out to be true ...

Hahaha! Indeed it might well be the reverse! I'm not a great fan of TV
nowadays, but when I DO want to sit down and watch something, I do want
it to work! I'll let things run as they are for a short while longer.

> It would probably ultimately be worth getting the antenna replaced with
> an up-to-date one, as you would then be guaranteed good reception under
> all weather conditions, but as I said before, choose your rigger with
> care. Have a look at the size and type of antennas that have appeared
> newly on your street. If they are not massive and very complicated
> looking, then you should be able to get a new one rigged on your house,
> again assuming that it's not a 'difficult' installation, complete with
> new cable, which will be very much better performing than the current
> cable you have, for less than 100 quid. A reputable rigger will not try
> to sell you anything different than anyone else in the street has, and
> will not try to persuade you to have a 'booster'. There have been a
> number of cases of disreputable riggers cashing in on this whole affair,
> and the public's lack of understanding of it, and plus 70 quid for a
> five quid un-needed Chinese amplifier, is one of the rip-off methods
> that has been used by them.

All your comments are most helpful, Thank you so much for taking the
time and trouble to advise me.

Have a great day! :-)

Thanks again, 'Arfa' (great nym!)

== 2 of 4 ==
Date: Thurs, Nov 3 2011 7:15 am
From: b

On this note, this site made me crease up with laughter.
scroll down to see some hilarous aerial bodges!
http://www.aerialsandtv.com/cowboyslocker.html#SelfRightingAerial

regards,
B.

== 3 of 4 ==
Date: Thurs, Nov 3 2011 8:02 am
From: ~BD~ <~BD~@nomail.afraid.org>

b wrote:
> On this note, this site made me crease up with laughter.
> scroll down to see some hilarous aerial bodges!
> http://www.aerialsandtv.com/cowboyslocker.html#SelfRightingAerial
>
> regards,
> B.

Great stuff! :-)

Thanks for posting!

== 4 of 4 ==
Date: Thurs, Nov 3 2011 5:41 pm
From: "Arfa Daily"

<snip>

>
> All your comments are most helpful, Thank you so much for taking the time
> and trouble to advise me.
>
> Have a great day! :-)
>
> Thanks again, 'Arfa' (great nym!)

Interestingly, a friend rang me this morning, to say that he was at the
house of a work colleague, and he was having a similar problem to you with a
Sammy 32". It actually kept reporting "Weak Signal" on the screen,
apparently.

I suggested that he did a complete 'new install' retune, to see what
happened. he rang back a couple of hours later to say that it was all now
sorted and working fine with quote "hundreds of channels". The only problem
that he had was that he reckons that he could not find a new install option
in the tuning sub-menu, so he did a bit of thinking outside the box, and
selected a 'wrong' country setting, and then asked it to do a retune. This,
he claims, caused it to find nothing, which cleared out the tuning memory,
so that when he set it back to "UK" and repeated the procedure, it found all
the correct multiplexes for where the antenna was pointing.

I was a bit sceptical about there not being a total reset option buried
somewhere 3 or 4 menu levels down, but whatever. His method did the job,
even if it was a bit around the houses ...

OK on the nic. It is of course my tongue-in-cheek tribute to the great
George Cole, and one of my favourite characters of his, Arthur Daley

Arfa

==============================================================================
TOPIC: Whirlpool WAOT11M00 11 Fins Price In India
http://groups.google.com/group/sci.electronics.repair/t/eab6bb74321affae?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Nov 3 2011 2:18 am
From: ritesh

Whirlpool WAOT11M00 11 Fins http://www.naaptol.com/price/723209-Whirlpool-WAOT11M00-11-Fins.html
Extra Safety Features, Electronic User Interface, Larger Surface Area,
Convenient 24 Hours Timer, 6th Sense Temperature Control Technology.

Disclaimer: Actual Product may vary in size, color and appearance. The
information provided on the page is subject to change as per the
upgradation in the product.

==============================================================================
TOPIC: Toshiba D-R160 DVD recorder, 2009
http://groups.google.com/group/sci.electronics.repair/t/5ef69f3de1c23bd1?hl=en
==============================================================================

== 1 of 2 ==
Date: Thurs, Nov 3 2011 3:47 am
From: "N_Cook"

Probably a generic DVD mechanics question.
One motor for sledge , optical deck up/down and drawer open/close.
Transported by courier and would not accept DVD when received at the other
end - box must have been jarred. Try pushing the drawer in and it knocks the
spinner motor assembly which is in the up / play position. The repair manual
only says replace the DVD unit in this situation. Removed this sub-unit,
N78E3CBN no info found. Delatched the drawer and removed , turned cogs and Z
track etc until only the drawer motion cog moved with no movement of sledge
or Z-rack and reintroduced the tray and optical unit in eject position. Is
this a standard approach to this symptom for direct coupled ie no drive
bands? Seems to work now - but just temporary or fixed proper for normal
use? No cracked /broken cogs/racks or free-floating pieces found.
The drawer seems very flimsey, I assume it flexed and a guide peg got on the
wrong side of a rail. Common problem? with a recognised correction of
beefing up somehow?

== 2 of 2 ==
Date: Thurs, Nov 3 2011 9:16 am
From: "N_Cook"

looks as though the optical deck jolted from eject to play position , in
transit. Then first use after , nasty scraping noise of drawer sliding over
the spinner.

==============================================================================
TOPIC: how hot should a schottky get?
http://groups.google.com/group/sci.electronics.repair/t/c666fc4f127ae347?hl=en
==============================================================================

== 1 of 5 ==
Date: Thurs, Nov 3 2011 6:54 am
From: b

My dvd-dtt unit recently failed to start up. As I suspected, there was
a bulged 1000uf 35v cap on the psu secondary so I changed it , and the
associated rectifier diode ( a 1N5822) as the pcb looked toasted and I
suspected it might have gone a bit leaky.

As replacement I used an SB340 ( http://pdf1.alldatasheet.com/datasheet-pdf/view/191268/WTE/SB340.html
) from the spares box. the unit now works but the diode seems to be
running hot - you can keep your finger on it - just - in use. Is this
usual? At least it doesn't seem to be getting red hot....
-B

== 2 of 5 ==
Date: Thurs, Nov 3 2011 9:14 am
From: "N_Cook"

b <reverend_rogers@yahoo.com> wrote in message
news:df1d105c-e21e-4cd0-964b-7b4e52968afd@s7g2000yqa.googlegroups.com...
> My dvd-dtt unit recently failed to start up. As I suspected, there was
> a bulged 1000uf 35v cap on the psu secondary so I changed it , and the
> associated rectifier diode ( a 1N5822) as the pcb looked toasted and I
> suspected it might have gone a bit leaky.
>
> As replacement I used an SB340
http://pdf1.alldatasheet.com/datasheet-pdf/view/191268/WTE/SB340.html
> ) from the spares box. the unit now works but the diode seems to be
> running hot - you can keep your finger on it - just - in use. Is this
> usual? At least it doesn't seem to be getting red hot....
> -B

what f is it handling ?

== 3 of 5 ==
Date: Thurs, Nov 3 2011 12:15 pm
From: spamtrap1888

On Nov 3, 6:54 am, b <reverend_rog...@yahoo.com> wrote:
> My dvd-dtt unit recently failed to start up. As I suspected, there was
> a bulged 1000uf 35v cap on the psu secondary so I changed it , and the
> associated rectifier diode ( a 1N5822) as the pcb looked toasted and I
> suspected it might have gone a bit leaky.
>
> As replacement I used an SB340 (http://pdf1.alldatasheet.com/datasheet-pdf/view/191268/WTE/SB340.html
> ) from the spares box. the unit now works but the diode seems to be
> running hot - you can keep your finger on it - just - in use. Is this
> usual? At least it doesn't seem to be getting red hot....
> -B

Absolute maximum current is 3A, at a forward drop of 0.5 V, so max
power dissipation is 1.5W. The typical thermal resistance is 20C/W, so
the max temperature rise should be 30 C. Can you keep your finger on a
55C temp surface?

Any $10 multimeter should be capable of measuring all three parameters.

== 4 of 5 ==
Date: Thurs, Nov 3 2011 5:40 pm
From: b

On Nov 3, 8:15 pm, spamtrap1888 <spamtrap1...@gmail.com> wrote:

>
> Absolute maximum current is 3A, at a forward drop of 0.5 V, so max
> power dissipation is 1.5W. The typical thermal resistance is 20C/W, so
> the max temperature rise should be 30 C. Can you keep your finger on a
> 55C temp surface?
>

Thanks for the suggestions guys.
left it on for a few more hours, and the temp. didn't seem to get out
of hand. Above calculations noted, many thanks.
I suspect this is just a poor design, the psu is a tiny crappy circuit
board, no regulators in sight just crude diodes and caps. Lots of pcb
area was scorched as things obviously ran hot/at the limits of their
tolerances from the word go.

Will do some more exhaustive soaktesting and if things deteriorate,
will check the voltage drop and current as sugested. For now I've just
got it off the bench for more pressing things.
regards, B.

== 5 of 5 ==
Date: Thurs, Nov 3 2011 6:50 pm
From: "hrhofmann@att.net"

On Nov 3, 7:40 pm, b <reverend_rog...@yahoo.com> wrote:
> On Nov 3, 8:15 pm, spamtrap1888 <spamtrap1...@gmail.com> wrote:
>
>
>
> > Absolute maximum current is 3A, at a forward drop of 0.5 V, so max
> > power dissipation is 1.5W. The typical thermal resistance is 20C/W, so
> > the max temperature rise should be 30 C. Can you keep your finger on a
> > 55C temp surface?
>
> Thanks for the suggestions guys.
> left it on for a few more hours, and the temp. didn't seem to get out
> of hand. Above calculations noted, many thanks.
> I suspect this is just a poor design, the psu is a tiny crappy circuit
> board, no regulators in sight just crude diodes and caps. Lots of pcb
> area was scorched as things obviously ran hot/at the limits of their
> tolerances from the word go.
>
>  Will do some more exhaustive soaktesting and if things deteriorate,
> will check the voltage drop and current as sugested. For now I've just
> got it off the bench for more pressing things.
> regards, B.

If you have any sort of a spare heatsink, it wouldn't hurt ot use it,
might help and can't hurt.

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