Toshiba TV29C90 problem; Image fades to black...

[Stein-Olav Lund]

Jerry G. wrote:

It would take a very large lightning hit to magnetize or damage a CRT.
The set would have been destroyed first! I think the screen became
magnetized, and should be able to be demagnetized.

This summer we had some thunderstorms here, luckily we don't have many.
The TV was on (counting seconds between flashes and thunder were typ.
10-20 seconds)
Suddenly it came closer, I heard a faint 'snap' which came from the area
where the TV and VCR was. The TV had a strange image: Green circle
inside the edges of the screen, 'dirt brown' colours inside this circle....
I immediately switched off and disconnected power and antenna plugs,
thinking 'why didn't I disconnect it at once'..
Later, when the storm passed, I connected the equipment again and
switched on. Luckily, the TV was fine again, the screen had probably
been magnetised as you said, but the power-on degaussing seemed sufficient.
As for the 'snap' I haven't found any visible or measurable faults...


Stein

 

[Watson A.Name - 'Watt Sun]

In article <3F3BB12B.CECCF4D4@shout.net>, berger@shout.net
mentioned...

You can still get them at some camera stores -- they're imported
from Poland.

Probably illegal to do that. There was a thread recently here on
someone who wanted to convert their camera to use alkaline cells to
replace the mercury cells which are no longer available.

Bill Janssen wrote:

Oh, I wasn't aware that Mecury cells were no longer available.

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Watson A.Name - 'Watt Sun]

In article <3F3C7B23.4F3014D8@earthlink.net>, robertbaer@earthlink.net
mentioned...

Jim Adney wrote:

On 13 Aug 2003 13:48:19 -0700 alanh_27@yahoo.com (Alan Horowitz)
wrote:

any of these new-fangled battery chemistries such that, buying an
average one off the shelf, it has a voltage that's within 1% of it's
nominal?

I seem to recall fresh ordinary carbon-zinc batteries being used as
"standards" in an earlier era. I think the voltage was supposed to be
1.56V, but that's a very old memory and could be off a bit.

-


I have never heard of using carbon-zinc (Leclanche) cells for any kind
of reference, and i have been an electronic technician for over 50
years.

When I was a youngster I got a VTVM that had instructions that had you
calibrate the DC range by measuring a fresh dry cell. Well, there
were no alkalines back then, everything was carbon-zinc.

[snip]

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Damir]

Could be a faulty power switch.
Did you check it?

Regards,
Damir

On 14 Aug 2003 16:32:32 -0700, puppy_friend@yahoo.com (David Yip) wrote:

Hi:

I have a Mitsubishi 91TXM monitor. It only turns on maybe 25% of
the time. It always makes all the right clicks and noises, but I only
get a picture about a quarter of the time. So I have to hit the power
switch about four times to get it going. Once it's going, it's solid
until I turn it off. How do I fix this? Isn't there a high voltage
that "jump" starts the tube? Could that be failing?

thanks,
David

 

[Loren Coe]

In article <oCV_a.1965$sx4.1448@fe05.atl2.webusenet.com>, jakdedert wrote:

"Sam Goldwasser" <sam@saul.cis.upenn.edu> wrote in message
news:6wwudfrhwe.fsf@saul.cis.upenn.edu...
"Clifton T. Sharp Jr." <clifto@clifto.com> writes:

Jerry G. wrote:
It would take a very large lightning hit to magnetize or damage a CRT.
The set would have been destroyed first! I think the screen became
magnetized, and should be able to be demagnetized.

[....]>> > to degauss; I was amazed when it fixed the problem.

Yes, the effects of a close lightning strike and nuclear EMP might be very
similar (at least in terms of magnetization of a CRT!).

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/

I had a strike around eight years ago which took out many, many electronic
devices in my home. Partial list includes vcr (no audio...video fine),
[....]
It literally blew my neighbors telco interface box off the wall of his
house...blew the bark off a stately old oak tree in my back yard (3" strip
running radially from the ground up to about 20'...mostly healed over now,
but I wonder if it will ultimately kill the tree).

this is the common result of tree strikes, in the Mt's of NM they
call it "cork screwing". the step up from this is when the trunk
actually explodes as the sap is vaporized inside the tree.

--Loren (formerly from Cloudcroft, NM)

 

[Dave D]

"David Yip" <puppy_friend@yahoo.com> wrote in message
news:a312e23c.0308141532.618f28ed@posting.google.com...

Hi:

I have a Mitsubishi 91TXM monitor. It only turns on maybe 25% of
the time. It always makes all the right clicks and noises, but I only
get a picture about a quarter of the time. So I have to hit the power
switch about four times to get it going. Once it's going, it's solid
until I turn it off. How do I fix this? Isn't there a high voltage
that "jump" starts the tube? Could that be failing?

thanks,
David

It's very unlikely to be anything to do with the tube. My bet is there's one
or more bad electrolytics in the PSU section, particularly the smaller ones
on the primary side. There may also be bad solder connections. It is a very
straightforward repair for an experienced tech, not a job for someone
unfamiliar with monitor repair due to shock hazards and the chance of doing
further damage.

Dave

 

[lcoe]

C. Stahl <cmstahl3815@yahoo.com> wrote:
[....]

My question is concerning two cordless phones that I have in my home
on two different phone lines. I currently have two 2.4Ghz cordless
phones, one an AT&T for my home line and one a Panasonic for a
business line. I have experienced that, when using the AT&T phone, if
a call comes in on the Panasonic, the call on the AT&T phone becomes
unintelligible (sounds like a bad cell phone connection). I haven't
had occasion where the calls have come in the reverse order, so I'm
not sure if the Panasonic behaves the same way.

I'm considering replacing the Panasonic 2.4Ghz, so I would then have
one AT&T 2.4Ghz and one AT&T 5.8Ghz.

Does anyone know whether having the two different phones on different
frequency ranges (as opposed to my current phones which both operate
at 2.4Ghz) would eliminate this interference when I have simultaneous
calls? > Any advice would be appreciated. Thanks in advance. > cmstahl

it should solve your problem, but be sure whatever phone you do get
has DSS, regardless of frequency. you may find a 900mhz DSS still,
this is the longest range phone ever produced, the comming "standards"
are from moderately shorter to less than 1/2 the that range, but offer
clearer channels.

i replaced my Vtech 900mhz DSS system (two phones on single base) with
a new 2.6gDSS unit. it has about 1/2 the range. the 5.2gDSS promise
better ranges but need lithium batteries. my old and new systems
both use ni-cads, and have long operating/stanby times (days).

Uniden's web site has a good page comparing the various freq phones.
the Vtech will not be scrapped, it is just too good to toss. may
sell or give to a relative, but will wait until i am sure about the
new system (lots of new features which inspired the upgrade). --Loren

 

[Jerry G.]

The frequency bands allocated for cordless phones is limited. The
frequencies are divided up in to channels. The better models are
supposed to do a frequency check to see the best channel or exact
frequency to use that is not occupied.

I have 2 Panasonic 2.4 gHz phones and 2 others that are 900 mHz phones.
They can all be used, and not interfere with each other. Infact, I am in
a high-rise building and many people here have these phones.

I tried some of the lower cost phones, and found that I had interference
problems. I had to opt out for the more expensive models to get rid of
this problem. This has to do with how they manage their frequency
allocation when addressed to be used.


--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"C. Stahl" <cmstahl3815@yahoo.com> wrote in message
news:4d414616.0308150622.e2b1b44@posting.google.com...
All --

Apologies if this is the wrong NG for this inquiry, but despite having
done some searches, was unable to find a more appropriate one. If
there is a more appropriate group, plse advise.

My question is concerning two cordless phones that I have in my home
on two different phone lines. I currently have two 2.4Ghz cordless
phones, one an AT&T for my home line and one a Panasonic for a
business line. I have experienced that, when using the AT&T phone, if
a call comes in on the Panasonic, the call on the AT&T phone becomes
unintelligible (sounds like a bad cell phone connection). I haven't
had occasion where the calls have come in the reverse order, so I'm
not sure if the Panasonic behaves the same way.

I'm considering replacing the Panasonic 2.4Ghz, so I would then have
one AT&T 2.4Ghz and one AT&T 5.8Ghz.

Does anyone know whether having the two different phones on different
frequency ranges (as opposed to my current phones which both operate
at 2.4Ghz) would eliminate this interference when I have simultaneous
calls?

Any advice would be appreciated. Thanks in advance.

cmstahl

 

[Leonard G. Caillouet]

David,
The discussion is about a guy's 5 year old Panasonic 27". The likelihood of
a doming problem on this one is much lower than a thermistor problem. If
you read the symptom he describes a problem in the corner as well as the
side. No none is saying that doming is not a potential problem, but
magnetic fields are very common on these sets due to degaussing circuit
problems.

Leonard Caillouet

"David" <dkuhajda@locl.net.spam> wrote in message
news:3f3c5d54@news.greennet.net...

If doming were really that rare, would RCA/Thomson, Zenith, Panasonic,
Toshiba, at a couple of lesser brands have all issued more than one
service
bulletin about the problem?

For a while a few years back it was big complaint on Toshiba and Thomson
32"
and 36" tv sets that were a few months into warranty.

David

Jerry G. <jerryg@total.net> wrote in message
news:bhge6f$fqn$1@news.eusc.inter.net...
There may be a few issues here. The degaussed circuit may not be
working properly. Sometimes when turning on the set, the screen may not
be properly degaussed. The thermosistor, and all the associated solder
connections should be checked. An experienced TV tech can service this
very easily.

There is the possibility that there is a magnetic field near to the set
that you are not aware of. If there are power wires with a heavy load on
them, that are within about 5 feet to the set, this can cause this
effect. There may be something on the other side of the wall from the
set that can cause problems, such as a large speaker, or device that has
a magnetic field.

As for the CRT having a defective mask, I sort of would rule this out
since you are indicating that the fault is not there all the time. This
means that it is clearable. I have seen defective masks in the CRT
cause this type of fault, but the fault could not be cleared.

There are rare occasions where for some reason the mask starts to have a
doming effect, especial when it gets warm. This means that something
became weak with the mask, and as it raises in temperature, it would
warp slightly. If this was the case, it should be very consistent, and
not go away.

Have the set properly checked by someone who really knows what they are
doing.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"Jeffrey Ellin" <deaduser@hotmail.com> wrote in message
news:e8a45386.0308131542.5c01e7bb@posting.google.com...
I have a 27" Panasonic TV which is about 5years old that has developed
a problem where periodically there are a greenish yellow splotches on
the screen in the left side and lower right corner. There aren't there
all the time. They almost look like there is a speaker near by which
there isn't. I was going to pitch this set until a tv repair tech from
Toshiba was at my house to work on another tv mentioned that it might
be a bad degausing circuit. He couldn't be sure because it wasn't
exhibiting the problem at the time. I tried to press him for some
information, but he was behind schedule and in a hurry to leave and of
course it wasn't a Toshiba set. It got me thinking though, how much
would it cost me to repair a degausing circuit and what is the
likelyhood that is the problem. I could take it in for an estimate,
but the set is dificult for me to move.

 

[Bill Janssen]

"Watson A.Name - 'Watt Sun'" wrote:

In article <3F3C7B23.4F3014D8@earthlink.net>, robertbaer@earthlink.net
mentioned...
Jim Adney wrote:

On 13 Aug 2003 13:48:19 -0700 alanh_27@yahoo.com (Alan Horowitz)
wrote:

any of these new-fangled battery chemistries such that, buying an
average one off the shelf, it has a voltage that's within 1% of it's
nominal?

I seem to recall fresh ordinary carbon-zinc batteries being used as
"standards" in an earlier era. I think the voltage was supposed to be
1.56V, but that's a very old memory and could be off a bit.

-


I have never heard of using carbon-zinc (Leclanche) cells for any kind
of reference, and i have been an electronic technician for over 50
years.

When I was a youngster I got a VTVM that had instructions that had you
calibrate the DC range by measuring a fresh dry cell. Well, there
were no alkalines back then, everything was carbon-zinc.

[snip]

Heath did that with a voltmeter kit that I put together. However, as I recall,
they
provided the D cell and the voltage that they measured in their lab. The
voltage
was only correct for that particular cell.

Bill K7NOM

 

[Chris]

Most definitely lightning can do this. This happened to RCA/GE (before
Thomson) at their warehouse in Tampa Florida. A lamp pole in their parking
lot was hit hard by lightning and destroyed the CRTs of almost 1000 sets. It
was the EMF, not the static, that was to blame. The electronics worked but
the CRTs were really messed up. Especially the larger ones.

"Bill" <elect21st@aol.com> wrote in message
news:8fb59540.0308132109.25d43d7f@posting.google.com...

Hello folks- I have an RCA TV chassis # CTC185AB. Customer said
after a severe storm he started getting weird colors on the screen.
Picture is perfect. I checked for blown parts and found none. I
resoldered some joints and replaced the deg. thermister just to be
sure. I also tried to clean these patches of color externally via a
deg. coil. I made some progress but the corners are still messed up.
I'm starting to believe he dropped it. Can storms do so much damage
that the screen can't be completely demagnetized ? What other
solutions are there in this case other than placing magnets on the CRT
? Thanks

 

[wpa]

FET or IGBT

Take care for isolation distances when designing the PCB!!

"AB" <artky1k@uninets.net> schreef in bericht
news:0gmbfv0it8l2l6nvrgsnjla25cee2p5itq@4ax.com...

Can anyone suggest a way to switch 400v DC?

I need to make 400vdc square wave from a 400v DC source that I already
have.

My switching frequency will be 50 to 75 Khz and I only need to switch
a few ma or 10 ma at the most.

I'm looking for something that doesn't waste alot of power, so my
guess is that a bipolar transformer with base current in the .1 ma
range is best.

A cmos gate can supply the input current to the switching transistor,
but I need suggestions regarding which transistor to use. The cmos
gate based oscillator is easy to build, and I prefer to use it to
drive the switching transistor.

This is for a battery operated ap, so leakage current should be
minimal.

Technically, I only need to switch about 300v, but I'd like to have a
safety factor, which is why I asked for a 400v switching suggestion.

Thanks all,

AB

 

[David]

You do a Google Groups search for Mitsubishi unlock.
This has been addressed many times in the past before.
You MUST have the remote control that came with the tv set.
The QV button is used in the sequence.
David

essingle@hotmail.com (essing) wrote in message news:<244de14d.0308151050.68701702@posting.google.com>...

The above mentioned TV is locked. How do you unlock it without knowing
the personal access code?

 

[David]

It looked like in his description that they came and went while
watching the tv set. Unless the degauss relay was stuck in the on
position, the degauss circuit would not have been doing this. If this
problem only happens on occasion right after turning it on, I would
expect a degauss circuit problem.

Some external magnetic field could however do something like this,
like a motor starting and stopping somewhere near the tv set.

5 year old set, 2003-5=1997. 97 is about when all the manufactures
had the biggest problems with tubes developing doming.

There just is not enough accurate information in the post of the
problem to really tell which way to look at it.

David

"Leonard G. Caillouet" <lcaillo_ns_@devoynet.com> wrote in message news:<2y9%a.2538$f44.800@fe04.atl2.webusenet.com>...

David,
The discussion is about a guy's 5 year old Panasonic 27". The likelihood of
a doming problem on this one is much lower than a thermistor problem. If
you read the symptom he describes a problem in the corner as well as the
side. No none is saying that doming is not a potential problem, but
magnetic fields are very common on these sets due to degaussing circuit
problems.

Leonard Caillouet

"David" <dkuhajda@locl.net.spam> wrote in message
news:3f3c5d54@news.greennet.net...
If doming were really that rare, would RCA/Thomson, Zenith, Panasonic,
Toshiba, at a couple of lesser brands have all issued more than one
service
bulletin about the problem?

For a while a few years back it was big complaint on Toshiba and Thomson
32"
and 36" tv sets that were a few months into warranty.

David

Jerry G. <jerryg@total.net> wrote in message
news:bhge6f$fqn$1@news.eusc.inter.net...
There may be a few issues here. The degaussed circuit may not be
working properly. Sometimes when turning on the set, the screen may not
be properly degaussed. The thermosistor, and all the associated solder
connections should be checked. An experienced TV tech can service this
very easily.

There is the possibility that there is a magnetic field near to the set
that you are not aware of. If there are power wires with a heavy load on
them, that are within about 5 feet to the set, this can cause this
effect. There may be something on the other side of the wall from the
set that can cause problems, such as a large speaker, or device that has
a magnetic field.

As for the CRT having a defective mask, I sort of would rule this out
since you are indicating that the fault is not there all the time. This
means that it is clearable. I have seen defective masks in the CRT
cause this type of fault, but the fault could not be cleared.

There are rare occasions where for some reason the mask starts to have a
doming effect, especial when it gets warm. This means that something
became weak with the mask, and as it raises in temperature, it would
warp slightly. If this was the case, it should be very consistent, and
not go away.

Have the set properly checked by someone who really knows what they are
doing.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"Jeffrey Ellin" <deaduser@hotmail.com> wrote in message
news:e8a45386.0308131542.5c01e7bb@posting.google.com...
I have a 27" Panasonic TV which is about 5years old that has developed
a problem where periodically there are a greenish yellow splotches on
the screen in the left side and lower right corner. There aren't there
all the time. They almost look like there is a speaker near by which
there isn't. I was going to pitch this set until a tv repair tech from
Toshiba was at my house to work on another tv mentioned that it might
be a bad degausing circuit. He couldn't be sure because it wasn't
exhibiting the problem at the time. I tried to press him for some
information, but he was behind schedule and in a hurry to leave and of
course it wasn't a Toshiba set. It got me thinking though, how much
would it cost me to repair a degausing circuit and what is the
likelyhood that is the problem. I could take it in for an estimate,
but the set is dificult for me to move.

 

[David Yip]

Damir:

Thanks for the response, but I doubt it's the power switch.
Because it always makes the right noises like the degauss cycle etc.
The LED comes on but 75% of the time, no picture.

David

Damir <vdamir@despammed.com> wrote in message news:<qaipjvga31e9vgqcr8i3pnecuv5to1mj8m@4ax.com>...

Could be a faulty power switch.
Did you check it?

Regards,
Damir

On 14 Aug 2003 16:32:32 -0700, puppy_friend@yahoo.com (David Yip) wrote:

Hi:

I have a Mitsubishi 91TXM monitor. It only turns on maybe 25% of
the time. It always makes all the right clicks and noises, but I only
get a picture about a quarter of the time. So I have to hit the power
switch about four times to get it going. Once it's going, it's solid
until I turn it off. How do I fix this? Isn't there a high voltage
that "jump" starts the tube? Could that be failing?

thanks,
David

 

[Jeff]

Manufacturer and Model would be a lot more info.
Jeff

"R3Jar" <r3jar@aol.com> wrote in message
news:20030815121400.21973.00000021@mb-m17.aol.com...

Does anybody know how a combination radio/cassette player senses the end
of
tape? I have a radio/cassette player in my Toyota Previa Van that started
to
periodically eject the tape or reverse itself. I dealt with it and it
continued
to work intermittently until now when I insert a tape it plays for about a
half
of a second and then ejects. I thought it might sense drag on the tape but
that
cannot be the cause. Can somebody tell me what to look for or how to
repair
this? This maybe an electronic problem as now I notice that if I try to
insert
a tape and press the fast forward or reverse buttons the radio goes to
radio
mode???? If I knew how it sensed the end of tape or what it senses to
reverse
and play I could repair it. I have removed the player from the vehicle and
also
the cassette mechanism and noticed a belt on the underside. Replace that
belt
with one very similar with no change of symtoms. Maybe bad motor? Hope
that
somebody knows something.
Thanks in advance

 

[Don]

Well, Dynaco tube amps used batteries as a reference in theiur biasing.
http://www.angelfire.com/ma2/AdamVon/dynaresto.html


In article <3F3C7B23.4F3014D8@earthlink.net>, robertbaer@earthlink.net says...

Jim Adney wrote:

On 13 Aug 2003 13:48:19 -0700 alanh_27@yahoo.com (Alan Horowitz)
wrote:

any of these new-fangled battery chemistries such that, buying an
average one off the shelf, it has a voltage that's within 1% of it's
nominal?

I seem to recall fresh ordinary carbon-zinc batteries being used as
"standards" in an earlier era. I think the voltage was supposed to be
1.56V, but that's a very old memory and could be off a bit.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

I have never heard of using carbon-zinc (Leclanche) cells for any kind
of reference, and i have been an electronic technician for over 50
years.
The mercury cells made reasonable inexpensive secondary standards, and
the voltage known to 4 digits (if i remember correctly) and could be
calibrated and used as transfer standards to 5 digits (if i remember
correctly).
It is my guess that the Lithium cells may be the best of the various
voltage sources, for that purpose.
However, one might do better using a 1.25V band-gap reference driven
from a Lithium cell.
There now seems to be an even better reference using a new technology;
see:
http://www.xicor.com/voltage_family.php

 

[GPE]

I'm also looking to switch high voltage controlled by a CMOS gate. But this
one's a tad harder. Need to be as small as possible and needs to switch a
load to ground. The load is operated at -150 volts DC (that's a negative
150 volts) at 25mA.

Any ideas?

TIA,
Ed

 

[TV Fixer1]

It's possible, but highly unlikely, as the speakers are magnetically shielded
to prevent that very thing

 

[Jerry G.]

The backplane light, or the ballast transformer for it may be going
defective. On some displays these parts are replicable if able to be
purchased from the manufacture.

Try calling their service department, and find out how much they would
charge to service your monitor. It may be worth it, if they are not
going to charge too much in relation to its age, and replacement value.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"Rob" <biddy67@hotmail.com> wrote in message
news:d986bfea.0308151842.1de150b1@posting.google.com...
My trusty Proview 768M has developed an occasional (about once an
hour) flicker that looks just like when you accidently tap the power
plug. Screen goes black and immediately restores itself. It is not
the power cord, jiggled it. The green "on" light remains sharp as
ever during the flicker incident. Wacking the side of the monitor
doesn't replicate the flicker. Any ideas? Might it be time to begin
looking for one of those sharp LCD screens?