Toshiba TV29C90 problem; Image fades to black...

[CRaSH]

Travis Jordan wrote:

Elbeva wrote:
I found this on a bulletin board and decided to try it. A little
while

What is a bulletin board?

a board from a bulletin tree.....

 

[rezwan]

Where did those addresses came from to start it with? What will happen
if everyone just keep the dollar and do nothing?

 

[sigmma]

sigmma:
No offence intended, but based on your inquiry you would be best
advised to
IMMJEDIATELY replace the TV cover and at the very least TAKE it to a
repair
shop for a repair cost estimate by a tech that has actually opened er
up and
performed some technical troubleshooting and testing so you can make
an
intelligent repair decision with facts instead of wild guesses.
The insides of televisions are a dangerous place.... if you want to
research
this further you should go to the website for this newsgroup at
http://www.repairfaq.org/
there with some searching you will find a wealth of repair data and
IMPORTANT SAFETY information.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair

Daniel Many thanks for your advice, I know that the inside of Tvs are a
really dangerous place, thats why I have decided to unplug the unit from
the wall before touching the flyback with my bare hands.....just
kidding!!!
now seriously, since I dont have a diagram for my Tv I have decided to
search for a faulty unit on ebay, Do you guys think that if someone is
selling a faulty unit and the fault being something like colour fading,
then the cause would be an aging tube and the chassis will be more o
less fine.....so if I replace the chassis from a another tv then I'll
have my Tv back....posible?????


--
sigmma

 

[ian field]

"sigmma" <sigmma.2894w0@diybanter.com> wrote in message
news:sigmma.2894w0@diybanter.com...

sigmma:
No offence intended, but based on your inquiry you would be best
advised to
IMMJEDIATELY replace the TV cover and at the very least TAKE it to a
repair
shop for a repair cost estimate by a tech that has actually opened er
up and
performed some technical troubleshooting and testing so you can make
an
intelligent repair decision with facts instead of wild guesses.
The insides of televisions are a dangerous place.... if you want to
research
this further you should go to the website for this newsgroup at
http://www.repairfaq.org/
there with some searching you will find a wealth of repair data and
IMPORTANT SAFETY information.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair



Daniel Many thanks for your advice, I know that the inside of Tvs are a
really dangerous place, thats why I have decided to unplug the unit from
the wall before touching the flyback with my bare hands.....just
kidding!!!
now seriously, since I dont have a diagram for my Tv I have decided to
search for a faulty unit on ebay, Do you guys think that if someone is
selling a faulty unit and the fault being something like colour fading,
then the cause would be an aging tube and the chassis will be more o
less fine.....so if I replace the chassis from a another tv then I'll
have my Tv back....posible?????


--
sigmma

Some less reputable service engineers make their living this way.

 

[Moydock]

Lenny Wrote:

This set clicks, the degausing coil energizes and thats all. Almost
every solder joint on the power supply board was cold. The Hor out in
circuit does not look shorted. I repaired the solder and the set is
still dead. There is an STRS6301 on the power supply board. I have
seen a few of these bad over the years and usually just replacing them
restores proper operation. However lately I've been reading about the
"A" version of this chip as being improved or better. Then again in
some forums it seems that its not recommended to replace an original
with an "A". Does anyone have any further insight on this? Also not
having a schematic, does anyone have a straight forward
troubleshooting procedure for this chassis or perhaps a published tip
on it that they could possibly share with me? Thanks very much for any
assistance you may be able to offer. Lenny Stein, Barlen Electronics.
I have the same set and i'm getting the same thing. I've never tried to

fix a tv but I ordered the STRS6301 b/c i'm too poor to have someone fix
it. I'm pretty good with electronics and i've soldered before. Can
anyone give me some pointers on how I should go about this? Preferably
some safety tips, maybe how to discharge the tv? I've had it unplugged
for 4 days now but I know that's not nearly long enough. I know i'm
suppose to keep 1 hand in my pocket at all times while working on it.
However, i'd really rather not get zapped so i'm trying to be as
careful as possible. Any guidance would be great, thanks.


--
Moydock

 

[sofie]

Moydock / Lenny:
I relace the STRS6301 with the "A" version ALL THE TIME.... not an issue or
problem...... but there are lots and lots of different things other than
the chip that can cause the symptom you reported but it is your money and
time.... and your television.
In addition to replacing the chip you should check for cracked solder
connections all over the power supply board.... and with your ESR meter
check ALL the electrolytics.... check for shorted power diodes on both
primary and secondary side of smps ..... also check around the flyback,
HOT, and HDr xfmr and resolder suspect connections..... as always, check for
shorted HOT.... and there are other various faults unrelated to the power
supply that can cause the symptom you are describing.
Failure to identify and repair these faults can result in premature failure
of the replacement chip.
SAFETY TIPS, repair procedures and troubleshooting information are found on
the website for this newsgroup at
http://www.repairfaq.org/
A MUST READ for the newbie television repair.
After reading the repairfaq if you are still not certain how to proceed and
do not have the proper test equipment including an ESR meter then you would
be best advised to TAKE your television to a service shop for at the very
least a repair cost estimate so you can make an intelligent repair decision
with facts instead of internet guesses. A knowledgeable tech with the
proper skills and test equipment will actually have to perform testing and
troubleshooting to determine the exact failure and faults before giving you
a firm repair cost estimate.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -



"Moydock" <Moydock.28bg82@diybanter.com> wrote in message
news:Moydock.28bg82@diybanter.com...

Lenny Wrote:

 

[Giluxis]

The fix is to initialize the eprom. Follow the proceedure that is
outlined in the service manual for replacement of QA02

Cheers

Jim

 

[shay-l]

I will be happy to get help in the assembler code for interfacing at89c51
to adc0809.

best regards
shay laicht.

 

[mm]

On Wed, 24 May 2006 00:08:24 GMT, "D&SW" <dsweatherwax@verizon.net>
wrote:

Years ago I tried to use a bridge and two 40mF 450V caps to banish some
nasty hum coming from two chandeliers, each with five 50W bulbs. Way too
much load for the caps. The hum remained and the caps were seconds away from
exploding due to their instant heat buildup. It might have worked with a
smaller load.

I don't get it. I thought that if the capacity of a cap was exceeded,
it just filled up on one side, and after that the rest of the current
behaved as if there were no cap. In fact it occurs to me that in a
DC power supply circuit for a radio or tv, the only reason the cap
ever gets below full charge is that the load is *high* enough to draw
more than is currently, during low parts of the cycle, being provided
through the diodes, so it drains the cap.

During the high points, the peaks of the 120 cycles per second power
(after rectification) there is more than enough power and that's when
the the caps are refilled.

Lowering the load would mean the cap would fill up on one side, and
then just stay filled all the time.

Two 40mF sounds like a lot, but if it wasn't enough, it seems to me
there would have been no current in or out of the caps after the first
charge.

If 80mF was enough to filter, maybe the internal leads couldn't handle
the current in and out without getting hot, even though current in and
out is what caps do. Maybe that level of heat was within range.

And I would also think that nothing 110 volts could do, even
full-rectified to make it higher than 110, could damage a 450V cap.

I would also wonder if caps are necessary, since an incandescent bulb
with pulsing DC current would remain hot and giving light, despite the
pulsing. Don't electronic dimmers work by completely turning off the
current parts of the time? And yet all we see is a constant but dimmer
light. They don't use caps at all except maybe little ones to make
them oscillate.


Posted and mailed because it's been almost 3 days and ahr is so busy,
I'm not sure anyone is reading this thread anymore. So I wanted the
poster to know I had replied.

"David D." <daviddiamond.remove-if-not-spam@comcast.net> wrote in message
news:99qdnalayLQLkezZ4p2dnA@comcast.com...
"mm" <NOPSAMmm2005@bigfoot.com> wrote in message
news:0mnv62lo2i5da62lklbn66s3tv8e6k5os3@4ax.com...
On Sat, 20 May 2006 16:35:29 GMT, CJT <abujlehc@prodigy.net> wrote:


I wonder whether a rectifier and capacitor between the dimmer and the
lamp would work (then the lamp would see DC). I bet somebody here
knows whether that would wreak havoc with the dimmer.

Since the output of the dimmer is still AC, that would dim it further.
by cutting the current in half, unless you used something like a
bridge rectifier (4 diodes arranged in a square) that is full wave.

(Sorry, maybe htat is what you mean to begin with.)

Then you'd be running yhour lightbulb on DC, and I would be very
intersted in how well that would work.

It would probably work, but, as a safety precaution, I would not want to
try
it. With AC, one would usually survive a mometary shock. 110-volt DC
can
burn severely.

- David

 

[Pooh Bear]

shay-l wrote:

I will be happy to get help in the assembler code for interfacing at89c51
to adc0809.

I bet you will. Why are you using assembler ? Too cheap to use a high level
language ?

A certain amount will depend on how you implemeted your circuitry anyway.

Graham

 

[Bud--]

mm wrote:

On Wed, 24 May 2006 00:08:24 GMT, "D&SW" <dsweatherwax@verizon.net
wrote:


Years ago I tried to use a bridge and two 40mF 450V caps to banish some
nasty hum coming from two chandeliers, each with five 50W bulbs. Way too
much load for the caps. The hum remained and the caps were seconds away from
exploding due to their instant heat buildup. It might have worked with a
smaller load.


I don't get it. I thought that if the capacity of a cap was exceeded,
it just filled up on one side, and after that the rest of the current
behaved as if there were no cap. In fact it occurs to me that in a
DC power supply circuit for a radio or tv, the only reason the cap
ever gets below full charge is that the load is *high* enough to draw
more than is currently, during low parts of the cycle, being provided
through the diodes, so it drains the cap.

In this case, the cap is way too small for the 250W load, and it is well
drained before the next 'fill up'.

During the high points, the peaks of the 120 cycles per second power
(after rectification) there is more than enough power and that's when
the the caps are refilled.

Lowering the load would mean the cap would fill up on one side, and
then just stay filled all the time.

Two 40mF sounds like a lot, but if it wasn't enough, it seems to me
there would have been no current in or out of the caps after the first
charge.

Since the cap is pretty fully drained, there is a very high current at
each 'fill up' followed by high current to the load that drains the cap.

If 80mF was enough to filter, maybe the internal leads couldn't handle
the current in and out without getting hot, even though current in and
out is what caps do. Maybe that level of heat was within range.

In addition to the leads, the capacitor has an internal resistance which
you might find specified as ESR (equivalent series resistance). Trying
to filter for light bulbs causes a relatively high current charging the
caps and then discharging to the lights. That will cause heating when
flowing through the capacitor's internal resistance. A reasonably sized
(larger) filter cap would have a far smaller ESR. But the dimmer may not
like the high peak currents to charge a large cap.

And I would also think that nothing 110 volts could do, even
full-rectified to make it higher than 110, could damage a 450V cap.

The AC voltage is a sinewave whose value is constantly changing. 110
volts is the RMS value - a form of average. The peak voltage is 1.4
times that - about 155 volts, which the cap would charge to with no
load. Far lower than 450V as you said.

I would also wonder if caps are necessary, since an incandescent bulb
with pulsing DC current would remain hot and giving light, despite the
pulsing. Don't electronic dimmers work by completely turning off the
current parts of the time? And yet all we see is a constant but dimmer
light. They don't use caps at all except maybe little ones to make
them oscillate.

Dimmers work by turning on late in each 'hump' in the sine wave. The
dimmer stays on until the next zero crossing. At full brightness the
dimmer turns on at the start of the 'hump'. At low brightness the dimmer
turns on late in the 'hump' and only the end of each 'hump' is there.
Rectifying just makes all the 'humps' positive instead of half being
positive and half being negative. The same basic waveform, which causes
the singing, is still there. Capacitor filtering would change the
waveform to DC. Series inductors, which some (all?) dimmers have also
changes the waveform, and if there is enough inductance will eliminate
singing.

bud--

 

[Peter Pan]

Always thought the singing to be related to the harmonics due from
phase control (the sound isn't 60 Hz), so the capacitors might not like
seeing all that harmonic current.

Also putting a capacitor parallel to the load shouldn't make it dc. The
capacitor had to be rather large, not to mention the need for some
rectifiers. This could be a way to filter out the harmonics on the
lamp.

In article <c867c$4479c949$4213ea2a$20644@DIALUPUSA.NET>, Bud--
<remove.BudNews@isp.com> wrote:

mm wrote:

On Wed, 24 May 2006 00:08:24 GMT, "D&SW" <dsweatherwax@verizon.net
wrote:


Years ago I tried to use a bridge and two 40mF 450V caps to banish some
nasty hum coming from two chandeliers, each with five 50W bulbs. Way too
much load for the caps. The hum remained and the caps were seconds away
from
exploding due to their instant heat buildup. It might have worked with a
smaller load.


I don't get it. I thought that if the capacity of a cap was exceeded,
it just filled up on one side, and after that the rest of the current
behaved as if there were no cap. In fact it occurs to me that in a
DC power supply circuit for a radio or tv, the only reason the cap
ever gets below full charge is that the load is *high* enough to draw
more than is currently, during low parts of the cycle, being provided
through the diodes, so it drains the cap.


In this case, the cap is way too small for the 250W load, and it is well
drained before the next 'fill up'.

During the high points, the peaks of the 120 cycles per second power
(after rectification) there is more than enough power and that's when
the the caps are refilled.

Lowering the load would mean the cap would fill up on one side, and
then just stay filled all the time.

Two 40mF sounds like a lot, but if it wasn't enough, it seems to me
there would have been no current in or out of the caps after the first
charge.


Since the cap is pretty fully drained, there is a very high current at
each 'fill up' followed by high current to the load that drains the cap.

If 80mF was enough to filter, maybe the internal leads couldn't handle
the current in and out without getting hot, even though current in and
out is what caps do. Maybe that level of heat was within range.


In addition to the leads, the capacitor has an internal resistance which
you might find specified as ESR (equivalent series resistance). Trying
to filter for light bulbs causes a relatively high current charging the
caps and then discharging to the lights. That will cause heating when
flowing through the capacitor's internal resistance. A reasonably sized
(larger) filter cap would have a far smaller ESR. But the dimmer may not
like the high peak currents to charge a large cap.

And I would also think that nothing 110 volts could do, even
full-rectified to make it higher than 110, could damage a 450V cap.


The AC voltage is a sinewave whose value is constantly changing. 110
volts is the RMS value - a form of average. The peak voltage is 1.4
times that - about 155 volts, which the cap would charge to with no
load. Far lower than 450V as you said.


I would also wonder if caps are necessary, since an incandescent bulb
with pulsing DC current would remain hot and giving light, despite the
pulsing. Don't electronic dimmers work by completely turning off the
current parts of the time? And yet all we see is a constant but dimmer
light. They don't use caps at all except maybe little ones to make
them oscillate.


Dimmers work by turning on late in each 'hump' in the sine wave. The
dimmer stays on until the next zero crossing. At full brightness the
dimmer turns on at the start of the 'hump'. At low brightness the dimmer
turns on late in the 'hump' and only the end of each 'hump' is there.
Rectifying just makes all the 'humps' positive instead of half being
positive and half being negative. The same basic waveform, which causes
the singing, is still there. Capacitor filtering would change the
waveform to DC. Series inductors, which some (all?) dimmers have also
changes the waveform, and if there is enough inductance will eliminate
singing.

bud--

 

[Weatherlawyer]

Weatherlawyer wrote:

Anyone know a site I can get a look at the internals of a scanner
before I take mine to bits and <s>throw it in the scrap.</s> repair it?

I might have no idea what I'm doing but I see no reason to let that get
in my way.

I would have thought there would be no end of strip downs of stuff like
that on the net. If there are I can't find them.

What a shame.

I was suprised to find the only advice given about scanners no longer
scanning is to dump them.

Whilst I have to admit that the state of computer parts and adjuncts
manufacture is no better than was the case with motor vehicle
manufacture when that mode of transport first became popular, at least
people did try to play with them to some success.

I don't see what cost effectiveness has to do with people messing
around with mechanical appliances. Have our young all been emasculated
by computer games or something?

I am a little upset at not being able to find at least a series of
photos of someone's non scanner in various states of no longer being,
at the very least. Our poor, poor children!

 

[g. beat]

"Weatherlawyer" <Weatherlawyer@hotmail.com> wrote in message
news:1148957383.823670.88710@j33g2000cwa.googlegroups.com...

Weatherlawyer wrote:
Anyone know a site I can get a look at the internals of a scanner
before I take mine to bits and <s>throw it in the scrap.</s> repair it?

I might have no idea what I'm doing but I see no reason to let that get
in my way.

I would have thought there would be no end of strip downs of stuff like
that on the net. If there are I can't find them.

What a shame.

I was surprised to find the only advice given about scanners no longer
scanning is to dump them.

Whilst I have to admit that the state of computer parts and adjuncts
manufacture is no better than was the case with motor vehicle
manufacture when that mode of transport first became popular, at least
people did try to play with them to some success.

I don't see what cost effectiveness has to do with people messing
around with mechanical appliances. Have our young all been emasculated
by computer games or something?

I am a little upset at not being able to find at least a series of
photos of someone's non scanner in various states of no longer being,
at the very least. Our poor, poor children!

Many of the scanners were designed and built in the 1970s and 1980s ..
Like the US space shuttle and some military aircraft -
some of the parts used are no longer manufactured (unobtanium ICs, etc.)

The normal consumer has a specific economic point where they are
willing to pay for the part - OR the labor to install it.

I guess you never hear about the Taiwanese disaster in 2002 for the
electronics industry?
The tale behind why the capacitor problem exists in the first place is
because of a large-scale industrial espionage foul-up. Some component
manufacturers decided to steal an electrolyte formula from another
competitor.
Little be known to them, the stolen formula was incomplete and flawed.
They didn't discover this until it was too late and they had manufactured
and distributed literally MILLIONS of these flawed capacitors.
http://www.badcaps.net/

One after effect, ASUS motherboard box (I saw yesterday) - proclaims they
use 100% quality Japanese capacitors !

g. beat

 

[gort]

Many of the scanners were designed and built in the 1970s and 1980s ..
Like the US space shuttle and some military aircraft -
some of the parts used are no longer manufactured (unobtanium ICs, etc.)

LOL, yes very good !!

 

[n cook]

Weatherlawyer <Weatherlawyer@hotmail.com> wrote in message
news:1148957383.823670.88710@j33g2000cwa.googlegroups.com...

Weatherlawyer wrote:
Anyone know a site I can get a look at the internals of a scanner
before I take mine to bits and <s>throw it in the scrap.</s> repair it?

I might have no idea what I'm doing but I see no reason to let that get
in my way.

I would have thought there would be no end of strip downs of stuff like
that on the net. If there are I can't find them.

What a shame.

I was suprised to find the only advice given about scanners no longer
scanning is to dump them.

Whilst I have to admit that the state of computer parts and adjuncts
manufacture is no better than was the case with motor vehicle
manufacture when that mode of transport first became popular, at least
people did try to play with them to some success.

I don't see what cost effectiveness has to do with people messing
around with mechanical appliances. Have our young all been emasculated
by computer games or something?

I am a little upset at not being able to find at least a series of
photos of someone's non scanner in various states of no longer being,
at the very least. Our poor, poor children!

If it was tube/amp stuff with 400V on anodes you could understand being very
cautious to the point of not even removing the covers , but pc ancilliary
kit out of bounds ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Weatherlawyer]

n cook wrote:

If it was tube/amp stuff with 400V on anodes you could understand being very
cautious to the point of not even removing the covers , but pc ancilliary
kit out of bounds ?

So give me some links to these exploits. It has occured to me that in
this day and age the sons of destruction engineering aught to have
pictures of more than scanner anatomies online.

Or are the pip squeaks only capable of copying and pasting the
anatomies of tennis players?

 

[Art]

Maybe it would be a good idea to at least post the manufacturere and model
number of the applicable device. Generic questions seem to mandate generic
answers.
Radio Shack items may need the service literature once marketed by Tandy
Corporation, the parent company of Radio Shack.
At least, when you post the make and model we would be a bit more informed
also.
"Weatherlawyer" <Weatherlawyer@hotmail.com> wrote in message
news:1148983519.902314.13800@y43g2000cwc.googlegroups.com...

n cook wrote:

If it was tube/amp stuff with 400V on anodes you could understand being
very
cautious to the point of not even removing the covers , but pc ancilliary
kit out of bounds ?

So give me some links to these exploits. It has occured to me that in
this day and age the sons of destruction engineering aught to have
pictures of more than scanner anatomies online.

Or are the pip squeaks only capable of copying and pasting the
anatomies of tennis players?

 

[Dave D]

"Jenwin" <jenniwinter@hotmail.com> wrote in message
news:1148999108.868260.236230@38g2000cwa.googlegroups.com...

I have Sharp VC-MH704 thats been working fine for the last 4/5 years
through the RF sockets, but never through scart.
It has even been used on 2 different TVs in this way with no problem.

However, now we have just purchased a JVC AV-28E50SK Digital Tv. (Also
purchased a DVD recorder and recently changed it to another model, but
problems occurs with both and without the dvd plugged in).

The problem is.....

The VCR will happily tune and playback the TV through both RF and Scart
sockets, but with either scart or RF plugged in, as well as both
plugged in, the video playback is distorted.

That seems to be a contradiction, it plays happily but it distorts? I don't
get it.

The picture is fine for about 5 seconds then it distorts diagonally
along and goes black and white with sound problems for about 3 seconds
and then is fine again and repeats.

We have tried every type of tv configuration in case of interferance
as well as playing using just the RF to connect as well as just the
Scart, but playback still has the same issue.

Tracking makes no difference.

We thought it may be interference, but no combination seems to help. Is
it a problem with the VCR or with the TV?

As i said the tv will happily use the ariel signal from the vcr to show
the tv channels.

It happens with all pre recorded videos, although we have no tried a
home recorded one, or even tried to record on the vcr.

Any ideas please? This is sending us nuts!!!! Will happily get the VCR
repaired or buy a new one if the problem is with it and not the new TV.

Try the VCR on other TVs. If it works fine it may be your new TV has a sync
fault or has been maladjusted at the factory. In layman's terms, VCR sync
isn't quite the same as broadcasted sync, which is why some old TVs required
a special video channel to cope with the difference.

Dave

 

[Mike Berger]

If you record and playback on the same machine, or play a tape
without macrovision copy protection, does the problem disappear?

Jenwin wrote:

I have Sharp VC-MH704 thats been working fine for the last 4/5 years
through the RF sockets, but never through scart.
It has even been used on 2 different TVs in this way with no problem.

However, now we have just purchased a JVC AV-28E50SK Digital Tv. (Also
purchased a DVD recorder and recently changed it to another model, but
problems occurs with both and without the dvd plugged in).

The problem is.....

The VCR will happily tune and playback the TV through both RF and Scart
sockets, but with either scart or RF plugged in, as well as both
plugged in, the video playback is distorted.

The picture is fine for about 5 seconds then it distorts diagonally
along and goes black and white with sound problems for about 3 seconds
and then is fine again and repeats.