Toshiba TV29C90 problem; Image fades to black...

ISRAEL FAGBEM · Mar 17, 2006

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JR North · Mar 17, 2006

Scope the audio path into and out of the stereo decoder, to the TDA 7132
output ICs when cold started and no audio. If OK, check the I/O cicuits
of the TDA 7132 chips.
JR

Karen Ray-Stewart wrote:

I am working on a Sanyo AVM-2547U Tv , all of the electrolytic caps
check out fine.There is no audio when you power it up. when it runs for
about 10 min. the audio slowly comes back, but it is garbled. their are two
IC's TDA 7132 audio output IC,s I freeze sprayed them but no change. I think
it could be the tuner? there is a 2 watt resistor in the supply right beside
it maybe causing this? any suggestions?

James

--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth

Bill Jeffrey · Mar 17, 2006

Dan wrote:

Tony Marsillo wrote:

Just for reference, here are my numbers for a SBV5120:

Downstream
Frequency: 603 MHz
S/N: 36 dB
Power Level: 5 dBmV

Upstream
Frequency: 33.024 mHz
Power Level: 30 dBmV

Thanks Tony, so your power level is 5, not NEGATIVE 5? (mine was -6.7)

Dan
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

And here are my numbers
Down
579 MHz
SNR = 34
Power = -5
Up
19.599667 MHz
Power 44 dBmV

I think the power level of -5 is OK. I seem to remember reading
somewhere that it should be above -10, and sure enough when mine was -10
was when I was ahving the trouble. The amp I spoke about is what raised
it to -5, and now I have no trouble.

Did you dig down into BroadbandReports.com? They keep changing the page
layout on the opening page, and it looks like they have reached a new
high in uselessness. But if you go down to
www.broadbandreports.com/tests and start looking around, it is a lot
more useful. In particular, I came across an entire section on Cable
Modem and Wiring Issues, and it touches on signal strength issues.

There is an entire saection on Comcast, one on Cox, one on Adelphia, etc.

Good luck.

Bill

Mr. Land · Mar 17, 2006

I just didn't like the final line.

I didn't like entering it, either, just don't want to see anyone get
hurt.

Charles Schuler · Mar 17, 2006

Bill et al- thanks for the replies and Bill especially for the very
useful site referral, I'd never seen that one before. I do have a
Motorola modem (SB5101). The downstream measurements are 711 mhz (so much
for the 60 meg scope ;-/ ), SN ratio of 34.9 dB & power level of -6.7
dBmV. Upstream is 23 mhz, 36.5 dBmV. If you can give me any insights
into the implications of these numbers, I'd appreciate it.

http://www.speedguide.net/read_articles.php?id=1197

Sorry that you are having trouble with Comcast ... that is not typical ... I
wonder what is different in your case? I'd suggest going to the top with a
letter or two. I find that letters have much more impact than emails and
phone calls.

Ray L. Volts · Mar 18, 2006

"Brad" <bpetria@verizon.net> wrote in message
news:441b2129.3250955@news.bellatlantic.net...

Hi,

From time to time, I come across an article about CD roms, etc.
What I have learned so far, CD-R (I use) is better than CD-RW for long
term storage of important data. Also, how they are stored can have
a bearing on their "life".

I keep CD roms in a dark cool location. To test the integrity of my
"burned" CD roms, I use "Finder" (search engine) I downloaded from
www.simtel.net. I "search" for a non-existant text pattern such as "i
don't
exist" in order to get "Finder" to read through every file on the CD rom
as a
way to check for corrupt data. Note: "Finder" has reported read errors on
some of my floppy disks. So far, no read errors were reported. However,
I
started burning CD roms about 4 years ago.

Is the integrity of commercial CD roms better than those I "burn" at
home?

Apples to oranges. Factory discs are not burned, they are pressed (i.e.,
molded) in the desired pattern. Writeable discs use dyes which are fixed by
the laser light to store the pattern. Hence, pressed CD's don't generally
degrade from subsequent exposure to the wrong kinds of light as do burned
discs. Extending the topic a little to DVD's, there is an unfortunate
phenomenon known as "rotting" which occurs even on factory discs. This
happens when defective bonding leads to layer separation.

How long can we expect to keep our CD roms, assuming they are stored in a
good
environment, before we begin to encounter corrupt data?

It varies. Assuming identical storage solutions, the main difference is in
brands used. But even that's hotly debated. You'll find users of the
cheapest crap on the planet proudly proclaiming their discs have lasted 5+
years, while others wouldn't touch them with a ten foot pole. Brand loyalty
comes into play as well. If you loved your old verbatim floppies, you might
want to stick with verbatim CD's, etc. I personally buy name brand
cakeboxes that offer the best value at that time. Usually, they end up
being TDK and Maxell, both of which have produced very good magnetic media
over the years and I have no prob trusting either company's CD's.

As a general rule of thumb with optical media, you should back up the most
precious data at least once a year. That includes DVD's. Data you can
afford to lose might get backed up once every few years. There's enough
evidence to clearly indicate the hype when writeable optical discs first
came out was utterly bogus. Your recording will last a hundred years!!??
Pretty funny.

Charles Schuler · Mar 18, 2006

Typical example of "topic drift":

"If one were to record this sound with a
microphone at 11 or 22Khz, would it be possible to obtain any information
(usable signal) from the recorded audio?"

The basic answer is still "NO."

JR North · Mar 18, 2006

My neighbors hate them

JR

Karen Ray-Stewart wrote:

Cool webpage,love the audio speakers!! I have been running a buisness in
repairs since 1994

--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth

Ken Weitzel · Mar 18, 2006

Ken Layton wrote:

íëěŹ wrote:

ęłľě§!ěŹěąęłź ěŚę¸°ë íě ěąí!
ëŹ´ëŁíŹě¸í¸ěŚě

1:1ëšë°ëíë°Š,ěë°í ëë§ě ë§ë¨~~

ěě ëĄě´ ěŚě ë˛ę°íę°ëĽ!

ě+ě +ë˛+í¸:ssx77
/a

-------------- ě¸í°ëˇ ěš´ëŚŹě¤ë§ KORNET -------------

What is this? A jumble of squares?

Hehe. Mail from China, "read" on a machine that doesn't have the
Chinese character set installed.

Ken

Ken

Mar 18, 2006

LA78041 will AN5522 be a direct sub?.Thanks.

Other part #'s for LA78041:

ECG/ NTE # NTE7182
Daewoo # 1LA78041
Funai # LA78041
JVC # LA78041
Orion # 103TD80410
Sanyo # 409 453 5905
Toshiba # AD300414
Toshiba old # BZ611118
Unknown OEM # 72794507
Zenith # 905-10653

Sidney
Dartmouth,Nova Scotia
Canada

O
|\ __O
_|_| \

(\__/)
(='.'=)
(")_(")

...><(((ş> ...><(((ş> ...><((((ş> ...><(((((ş>

..(....\............../....)..
...\....\........... /..../..
....\....\.._.._../..../....
.....\..../....l..`\_./....
...../....l....l....(..`\....
....l.....l.._.l.._.\....\...
....l.....l__.l__.l''\....\..
....\...................\../..
......\__________/.....

() () ^
() () / \ ^ ^
() () / \ \ ^ / \
| | / \ \ \____________ o o )
| | /_________\___\__\__________|_____|

JR North · Mar 18, 2006

No,no...there's a little guy standing on it wearing a hard hat with a
flashing light on top, waving a flag that sez: "tuning circuit"
JR

Just Another Theremin Fan wrote:

if this is true how do I recognise the tuning circuit?

It has a little label on it marked "tuning circuit".

--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth

Sam Goldwasser · Mar 18, 2006

jakdedert <jakdedert@bellsouth.net> writes:

One thing i learned recently about optical disks disturbed me. I had
always taken the most care to protect the data side of the disk. I
found out that the most fragile side is actually the one with the
label. It's the one closest to the actual media. A scratch there--one
which might not even glitch a reader if it were on the other side--can
expose the metallic layer to corrosion.

Yeah, and a piece of sticky tape may pull it off entirely on CD-R/RWs!

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Edd Whatley · Mar 18, 2006

..1 ufd
63 VDC (or pulsating DC)
2% tolerance
Polyester cap

73's de Edd

--
Edd Whatley

Smitty Two · Mar 18, 2006

In article <JiTSf.7986$u31.5021@newsfe2-win.ntli.net>,
"Arfa Daily" <arfa.daily@ntlworld.com> wrote:

"Edd Whatley" <Edd.Whatley.24v2dk@diybanter.com> wrote in message
news:Edd.Whatley.24v2dk@diybanter.com...

1 ufd
63 VDC (or pulsating DC)
2% tolerance
Polyester cap

73's de Edd

--
Edd Whatley

Hi Edd

Interested to know how you arrived at a value of one mic rather than point
one. I was assuming that the " 100 " was 100nF, as it is common convention
to mark caps in nF's ?? Mic ( no pun !! ) back to you sir ...

Arfa

Edd's post showed up on my server as point one. My dad was a college
professor and he always deducted one point for answers less than one
that did not include a leading zero. Too easy for that decimal point to
get lost, or be confused with a speck of fly shit.

kip · Mar 18, 2006

Check Voltage on Pin 2 and 3 ,this is not your
regular Vert IC it has 2 supply voltages.
Maybe one is missing !!! if not change it.
Also change the filter caps associated with it.

kip

"Wayne Tiffany" <waynetiffany(RMVJUNK)@netzero.net> wrote in message
news:dvh6hh$dhp8$1@news3.infoave.net...

Sony KV-24FS100 television
Chassis BA-6

I agreed to look at this set for a friend at work and I am sort of stuck.
She said she was watching it just fine, glanced away, and when she looked
back, the top half of the picture was gone - just black. I fired it up
and find that the top half has collapsed. The bottom half is just fine -
full color, no foldover into that area, etc. I do, however, find that if I
hit the tv/video button on the remote, then in what I presume are the
video modes, the whole screen collapses into a horizontal line at the
middle. Keep pushing the button and when it gets back to the tv mode, the
bottom half returns.

I searched for this issue online (here and otherwise) and not found it
mentioned anywhere, so I started in. I found and downloaded the service
manual, so I have the schematics. The first thing I checked was the
electrolytic caps around the vertical output chip (TDA8172). ESR was way
high on 2, and marginal on 3 more so I replaced all 5. I also checked
all the resistors that attach to that chp and all appeared to pretty well
match the schematic. No change in action.

So, that's where I am now. My next thought is to replace the TDA8172
chip, but I would appreciate the opinion of the more experienced people
here. Any thoughts? Thanks.

WT

Jim Yanik · Mar 18, 2006

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6wzmjo306e.fsf@saul.cis.upenn.edu:

Jim Yanik <jyanik@abuse.gov> writes:

"Ancient_Hacker" <grg2@comcast.net> wrote in
news:1142617094.382451.289320@j52g2000cwj.googlegroups.com:

Oh, there's also a big voltage divider resistor (the white ceramic
thing) Any moisture, dust, or leakage there and you tend to get
unstable HV.

The HV thick-film resistor network(TEK-made) has the HV feedback for
regulation on one side,and the CRT focus divider on the other. Either
one can go out-of-tolerance,and the metal pins can crack and be
intermittent.I've never been successful in resoldering them,either.

I do not think this part would be the cause of his intensity
modulation.

Followup: The frequency of the chopped line does NOT correlate with
line frequency.

Perhaps HV oscillator freq?

And I should note that at low intensity, it is worst going full off.
With the intensity turned up, it's not visible. There is minimal
if any geometric distortion of the trace (outside of the focus
problem, which doesn't always appear) so I doubt any LV power supplies
are involved that also feed the amps.

Then you're down to decoupling caps.

It's almost as if the Z input has some oscillation on it. When I
first noticed, I thought maybe the chopped blanking was misbehaving,
but this occurs on all vertical modes.

A thought occurs to me;there's a 1uf/150V(IIRC) electrolytic on the wiper
of the CRT grid bias pot,to ground;that could be going bad.

It's also related to warmup. At power-on, there is no problem. It
takes a of couple minutes to show up. The fan is running.

And even then, the severity varies randomly.

So, what could affect the Z modulation AND sometimes focus, but not
geometry?

If it was the HV divider I guess a parts unit is the only source for a
replacement?

Yes,it was a TEK-made part,from their defunct hybrid/ICO in-house plant.
Removing a good one from a motherboard without damaging it is not an easy
task

--
Jim Yanik
jyanik
at
kua.net

Sam Goldwasser · Mar 21, 2006

"alkaprim@gmail.com" <alkaprim@gmail.com> writes:

Sam Goldwasser wrote:
You could ring test the trensformer....

How do I do that ? I mean whats the easiest way to do that , preferably
without desoldering it?

It's still low on the probability scale but eliminating the transformer
as a likely problem could prevent you from going down a bunch of dead
ends.

See the Flyback Testing FAQ:

http://www.repairfaq.org/sam/flytest.htm

You will probably want to desolder it though.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

David C. Partridge · Mar 21, 2006

I'd think that any PNP power xistor with an adequate voltage rating would
do - this is just a pass xistor wired as an EF isn't it?

David

"Dave" <dspear99ca@yahoo.delete.com> wrote in message
news:%CVTf.6013$J43.2877@edtnps90...

I've identified a bad transistor in the power supply of an audio
component,
circa 1981. It's a 2SB527 PNP transistor... I had a bit of a look around
on
the net and didn't find any quick easy sources. This transistor's sole
function is to convert -26VDC coming off one side of a bridge rectifier
to -13 volts. [snip]

Gerard Bok · Mar 21, 2006

On Tue, 21 Mar 2006 14:06:54 -0000, "n cook" <diverse8@gazeta.pl>
wrote:

Other than cleaning mirrors & lenses anyone any ideas on how to bring the
exposure level up to get black on light grey rather than black on almost
equally dark black background.
Anyone tried translucent thin but very white plastic sheet of some sort
overlaying the original. ?
Reducing the exposure masking increases the exposure but whites out the fine
details.
The paper has gone very brown from air bourne SO2/SO3 , neutralising the
paper with alkali improves things but tends to lighten the black image so no
further forward as far as contrast.

One way would be, to scan them into your PC and apply some kind
of color filtering.
May take some effort to get the right filter settings, but in the
end you get 'as new' printouts

--
Kind regards,
Gerard Bok

Dave · Mar 21, 2006

"David C. Partridge" <afb12xwy@dialxwy.pipex.com> wrote in message
news:C8adnUQjLNMTur3ZRVnyuA@pipex.net...

I'd think that any PNP power xistor with an adequate voltage rating would
do - this is just a pass xistor wired as an EF isn't it?

David

I know very little of transistors other than their basic function, so I

don't know the answer to your question above.

As I noted, it's being used to (down)-regulate negative DC voltage. What
might the reason have been to opt for this transistor over a regulator?
There is a +5VDC regulator right next door in the same circuit.

Can I use the regulator in place of the transistor?

Toshiba TV29C90 problem; Image fades to black...

ISRAEL FAGBEM

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