Toshiba TV29C90 problem; Image fades to black...

In article <4846b1Fic30cU3@uni-berlin.de>,
JANA <jana@ca.inter.net> wrote:
In reality, these lamps are lasting about 800 to 1000 hours if you are
lucky. I know some people that are changing these lamps about once a
year.
Click to expand...
My Sagem DLP has a warranty for 5 years which includes the lamp. 3 years
from the maker and an extra 2 from the store.

--
*When blondes have more fun, do they know it?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
Howdy Scott.....sounds like time to get a schematic and dig out a scope.
Output (speaker) back to input and see where your noise is originating
from. Wish I had a "silver bullet" for your problem but thats where I'd
be (and have been many times).
 
In article <441E0528.2090700@nbnet.nb.ca>,
G <skiffingNOSPAM@nbnet.nb.ca> wrote:
Howdy Scott.....sounds like time to get a schematic and dig out a scope.
Output (speaker) back to input and see where your noise is originating
from. Wish I had a "silver bullet" for your problem but thats where I'd
be (and have been many times).
Click to expand...

Think I found the silver bullet! ;-)

Since this radio is well out of warranty, I opted to remove the back
cover. It revealed a circuit board. After a casual look around the
inside, I discovered the board was connected to another circuit board.

I happened to have the batteries installed and the radio on.

After checking the connections and seeing what was where, I discovered the
"top" circuit board (what is first revealed when the back is removed)
became loose from the "bottom" circuit board. I also learned it is
connected via a simple surface-mount connector (familiar kind, but I
forget its name at the moment). I also discovered I lost volume/squelch.

When I reconnected the "top" board to the "bottom" board via that
connector, the volume returned (squelch was open by chance). I turned the
squelch closed, and the speaker became quiet.

Apparently, the connector between the boards had become lose.

Simple solution!

Scott
 
On Fri, 17 Mar 2006 20:58:18 GMT, bpetria@verizon.net (Brad) put
finger to keyboard and composed:

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.
Click to expand...
Is that for the Windows platform? If so, doesn't Windows' built-in
"Find Files and Folders" function do the same thing?

Otherwise, try this from a DOS prompt:

echo f | xcopy d:\ nul /c /h /s > %temp%.\readtest.txt

This reads every file on the CD-ROM (drive D:) and copies it to the
NUL device, ie into the bit bucket. The results of each read are
recorded in readtest.txt.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
Good job Scott! Every repair should start with a look and smell -
guess I'd assumed you'd had the covers off already.

Good listening.

Gord
 
Sam Goldwasser wrote:
sck0006 writes:

On 18 Mar 2006 12:40:11 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu
wrote:

Does anyone know of a free source for decent quality schematics?
***

Thanks. That would probably be adequate. There's no problem with the text
of the manuals, just the schematics. And this problem would seem to be
associated either with the power supplies or the CRT bias/intensity/Z
input circuits.
Click to expand...
I found the 465B manual from bama.sbc.edu is nice: I can read the
schematics easily, and quality is alright for my repair purposes. Sam,
did you try this free source? don't forget about bama mirror at
edebris, for faster download.

Only thing you have to do extra is that you have to install the free
reader, for .djvu format. Even if it is old, it still works adequate.


hth,
Andreas
 
Isn't it easier and safer with a CRT rejuvenator?


--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
jstielau@snet.net
========================

"Dani" <greeben@gmail.com> wrote in message
news:1142696464.033824.14310@i40g2000cwc.googlegroups.com...
I would like to share this great tip with all you great helpfull Tech's
out there! This is only for Technicians who really know there way
around the inside of a T.V.! Please don't just anyone try this!! If you
don't have a proper CRT rejuvinating set, this will be a great fix, for
an otherwise lost cause.

Sony 1 K problems, that is T.V.'s with the red, or green, or blue
having too low, or high of an emission to get a raster due to the
"blanking circuit", can be solved with an odd, & somewhat dangerous
technique! With the set off, unsolder each cathode on the CRT board,
then momentarily bridge the gap of each gun, one at a time, to see how
much emission there is. You will have to raise the G 2 pot to get a bit
of raster in a darkened room! Next solder the two good cathodes
(usually only one is out of gain specs), back, leaving the bad one. Now
this is where it gets dangerous!!! While the set is off remove the
focus line from the CRT socket ( 5000 volts), & while the set is
running, momentarily make contact with the unsoldered leg of the bad
gun. Do this with caution, & at least five times. It will try to arc,
but just keep a steady hand, & keep the wire with a good insulated tool
at the unsoldered leg only. Now, while the set is off, unhook the G 2
wire, & set it to about 200 volts DC unloaded, & charge a 100 uf
capacitor @ 250 volts. Do this two, or three times, then discharge it
to the unsoldered gun, while the set is runing. Do this charging, &
discharging to the gun at least five times! At this point, you should
see the bad gun get brighter, & brighter. I have done quite a lot of
experimenting, & this will save a lot of those Sony CRT's, that would
otherwise be toast. Grey scale comes back to within a close enough
spec, to make the customer happy. Just don't give a long warranty. Hope
this helps you all out. Take care, Dani.
Click to expand...
 
"Andreas Tekman" <and7@bigfoot.com> writes:

Sam Goldwasser wrote:
sck0006 writes:

On 18 Mar 2006 12:40:11 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu
wrote:

Does anyone know of a free source for decent quality schematics?
***

Thanks. That would probably be adequate. There's no problem with the text
of the manuals, just the schematics. And this problem would seem to be
associated either with the power supplies or the CRT bias/intensity/Z
input circuits.



I found the 465B manual from bama.sbc.edu is nice: I can read the
schematics easily, and quality is alright for my repair purposes. Sam,
did you try this free source? don't forget about bama mirror at
edebris, for faster download.

Only thing you have to do extra is that you have to install the free
reader, for .djvu format. Even if it is old, it still works adequate.
Click to expand...
That looks much better than the ones I have. Thanks. I knew
about the bama Web site but never bothered to download the djvu reader
before.

Any hints on getting pages to print with reasonable quality?

--- 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.
 
On 18 Mar 2006 19:54:37 -0500 Sam Goldwasser <sam@saul.cis.upenn.edu>
wrote in Message id: <6wfylfi78y.fsf@saul.cis.upenn.edu>:

Thanks. That would probably be adequate. There's no problem with the text
of the manuals, just the schematics. And this problem would seem to be
associated either with the power supplies or the CRT bias/intensity/Z
input circuits.
Click to expand...
Check your mail.
 
In sci.electronics.components Neil J. Harris <neil@njharris.demon.co.uk> wrote:
: Hi,
: Have you tried Grandata, http://www.grandata.co.uk , they list them at
: ?1.50 + ?1.00 p&p +VAT.

Yep. I even placed an order, only to find out later that they had no stock
and were not able to source any either :-(.

Cheers
Tom.

: In message <dv9u5m$1po$1@mklab.ph.rhul.ac.uk>,
: UHAP023@alpha1.rhbnc.ac.uk writes
: >Dear All,
: > Can anybody suggest a reasonably priced (less than ?15) source
: >of 1 or 2-off TDA1024 chip. It is a now obsolete thermostat
: >controller chip which drives a triac.

: --
: Neil J. Harris

--
Tom Crane, Dept. Physics, Royal Holloway, University of London, Egham Hill,
Egham, Surrey, TW20 0EX, England.
Email: T.Crane@rhul.ac.uk
Fax: +44 (0) 1784 472794
 
Thanks for your replies.
I originally thought that the problem was of the usual dry solder
joint type but now I'm not so sure.

Switching the TV off and on using the standby buttontakes less than a
quarter of a second and it always fixes the picture if only for a
little while. I wouldn't expect this if it was a problem with heat
expansion of a circuit board. Also the room temperature doesn't seem
to make any difference. The connector at the neck of the tube still
glows when the tube has gone off.

I don't know too much about electronics, I'm a former electrician so I
have a grasp of the basics but could it be something to do with a part
of a circuit discharging when the picture is switched off? Or voltage
regulation perhaps? I told you I don't know too much electronics!

I had hoped that the fault would be of a type that someone would
recognise as a particular one.
Otherwise I will have to take Jerry G's advice and take it to a
repairer.
 
<captainvideo462002@yahoo.com> wrote in message
news:1142445107.874278.126800@v46g2000cwv.googlegroups.com...
I replaced two noisey intermittent preamp transistors in one channel of
this unit with NTE324's. These are supposed to be a direct replacement
for the originals. The unit seems to work well. All transistors in both
channels under quiescent conditions seem to run cool enough and there
is no noticeable distortion when driving the amps at sufficient volume.
However I have noticed that after a few minutes at sustained loud
volume the complementary output transistors on the repaired channel
seem to be running noticeably warmer than the other. They are nowhere
near "alarmingly" warm but just enough to let me know that there is a
difference. I have taken some comparative voltage measurements between
both channels and as expected have noted some differences. I have
attempted to tweak the bias pot on the repaired channel to even things
out between the two channels but it seemes like for instance if I
adjust the pot so that the emitter on one of the outputs matches the
same transistor on the the other channel it throws sonmething else off.
Should I just go for 0volts at the midpoint of the two outputs at the
big inductor or might there be more to it than that? Without the
service manual I don't know where to make the measuremenrt or what to
adjust it for. This appears to be a direct coupled amp with 4A fuses to
the speakers and without a capacitor on the output. I've seen
amplifiers of this type destroy speakers before so I don't want to make
a mistake with this. Can anyone advise me further. Thanks for any
assistance. Lenny Stein, Barlen Electronics.
Click to expand...
Hi Lenny,

The service manual says:

Hook up an 8 ohm dummy load to "A" speakers. Set function switch to AUX with
no input. Let the set warm up for 10 minutes. Connect dc voltmeter to pins
21 and 17. Adjust VR1 for 20mv. For the other channel, use pins 8 and 11 and
adjust VR2.

Hope this helps.

--
David Farber
David Farber's Service Center
L.A., CA
 
On 20 Mar 2006 10:15:33 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu>
wrote:

"Andreas Tekman" <and7@bigfoot.com> writes:

Sam Goldwasser wrote:
sck0006 writes:

On 18 Mar 2006 12:40:11 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu
wrote:

Does anyone know of a free source for decent quality schematics?
***

Thanks. That would probably be adequate. There's no problem with the text
of the manuals, just the schematics. And this problem would seem to be
associated either with the power supplies or the CRT bias/intensity/Z
input circuits.



I found the 465B manual from bama.sbc.edu is nice: I can read the
schematics easily, and quality is alright for my repair purposes. Sam,
did you try this free source? don't forget about bama mirror at
edebris, for faster download.

Only thing you have to do extra is that you have to install the free
reader, for .djvu format. Even if it is old, it still works adequate.

That looks much better than the ones I have. Thanks. I knew
about the bama Web site but never bothered to download the djvu reader
before.

Any hints on getting pages to print with reasonable quality?

--- 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.
Click to expand...
I've got the schematics if you still want them. I was only able to
get horizontal amplifier, crt circuit, power supply, and the power
supply troubleshooting sections. Let me know...

Steve
 
Thanks very much for the help. It went out of here the other day. best
regards, Lenny Stein.
 
sck0006 writes:

On 20 Mar 2006 10:15:33 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu
wrote:

"Andreas Tekman" <and7@bigfoot.com> writes:

Sam Goldwasser wrote:
sck0006 writes:

On 18 Mar 2006 12:40:11 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu
wrote:

Does anyone know of a free source for decent quality schematics?
***

Thanks. That would probably be adequate. There's no problem with the text
of the manuals, just the schematics. And this problem would seem to be
associated either with the power supplies or the CRT bias/intensity/Z
input circuits.



I found the 465B manual from bama.sbc.edu is nice: I can read the
schematics easily, and quality is alright for my repair purposes. Sam,
did you try this free source? don't forget about bama mirror at
edebris, for faster download.

Only thing you have to do extra is that you have to install the free
reader, for .djvu format. Even if it is old, it still works adequate.

That looks much better than the ones I have. Thanks. I knew
about the bama Web site but never bothered to download the djvu reader
before.

Any hints on getting pages to print with reasonable quality?

I've got the schematics if you still want them. I was only able to
get horizontal amplifier, crt circuit, power supply, and the power
supply troubleshooting sections. Let me know...
Click to expand...
Thanks but I think what I was able to get from the bama Web site is
quite legible, if a pain to print. Printing from within the djvu reader
results in poor quality, at least with my printer. I now export the
page to a .bmp file and print it in sections. I think all I should need
is the CRT circuit and I've printed that.

I'm just surprised that with all the 465Bs out there, no one has come forward
to say they've seen this problem before.

--- 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.
 
On 20 Mar 2006 21:52:38 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu>
wrote:

sck0006 writes:

On 20 Mar 2006 10:15:33 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu
wrote:

"Andreas Tekman" <and7@bigfoot.com> writes:

Sam Goldwasser wrote:
sck0006 writes:

On 18 Mar 2006 12:40:11 -0500, Sam Goldwasser <sam@saul.cis.upenn.edu
wrote:

Does anyone know of a free source for decent quality schematics?
***

Thanks. That would probably be adequate. There's no problem with the text
of the manuals, just the schematics. And this problem would seem to be
associated either with the power supplies or the CRT bias/intensity/Z
input circuits.



I found the 465B manual from bama.sbc.edu is nice: I can read the
schematics easily, and quality is alright for my repair purposes. Sam,
did you try this free source? don't forget about bama mirror at
edebris, for faster download.

Only thing you have to do extra is that you have to install the free
reader, for .djvu format. Even if it is old, it still works adequate.

That looks much better than the ones I have. Thanks. I knew
about the bama Web site but never bothered to download the djvu reader
before.

Any hints on getting pages to print with reasonable quality?

I've got the schematics if you still want them. I was only able to
get horizontal amplifier, crt circuit, power supply, and the power
supply troubleshooting sections. Let me know...

Thanks but I think what I was able to get from the bama Web site is
quite legible, if a pain to print. Printing from within the djvu reader
results in poor quality, at least with my printer. I now export the
page to a .bmp file and print it in sections. I think all I should need
is the CRT circuit and I've printed that.

I'm just surprised that with all the 465Bs out there, no one has come forward
to say they've seen this problem before.

--- 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.
Click to expand...
Glad you got what you needed. It is a strange problem that you have,
I hope you can track it down. My T-935A has a problem sort of similar
to what you're describing, but it is by no means periodic noise and
seems to be much more like a dirty intensity pot. It has a chopped
appearance, but just looks like dirty pot noise instead of what you're
describing. I haven't had any desire to take it back apart, too many
other things to do. Best of luck.

Steve
 
"Jerry G." <jerryg50@hotmail.com> wrote in message
news:1142965470.429561.103560@i39g2000cwa.googlegroups.com...
In these, usually it is the HV multiplier, or the CRT is failing. In
most cases it was the HV miltiplier.


Jerry G.

--
Click to expand...
I'm no expert on monitors, but wouldn't an HT problem cause an equal loss of
focus in all directions, instead of what I'm getting, which is a loss of
focus, or blurring of some kind, only in the horizontal direction?
To me it looks as I'd imagine it would if a very high frequency sine wave
was modulating the horizontal deflection voltage by a few percent. Or if
these things have independent horizontal and vertical focus (I can't imagine
how???), then I'd suspect the horizontal focus circuit had an intermittent
fault.
Thanks,
Scrim
 
Howdy Dave......I like your simple solution to use a 7915 from your junk
box and in the process, simplifying your circuitry a little! Of course
my first choice would have been something like a 7912 with a single gen
purpose diode (1N4001 etc) inserted in the leg to ground to bump the reg
voltage output up nearer to 13. With your 7915 you could likewise add a
couple of similar diodes in series with the output to lower the voltage
to your load.

Keep on tinkering.


Gord
 
"G" <skiffing@nbnet.nb.ca> wrote in message
news:44208383.1010605@nbnet.nb.ca...
Howdy Dave......I like your simple solution to use a 7915 from your junk
box and in the process, simplifying your circuitry a little! Of course
my first choice would have been something like a 7912 with a single gen
purpose diode (1N4001 etc) inserted in the leg to ground to bump the reg
voltage output up nearer to 13. With your 7915 you could likewise add a
couple of similar diodes in series with the output to lower the voltage
to your load.

Keep on tinkering.
Click to expand...
I'd like to go the diode route as they are more readily available than any
particular transistor. How would I wire them up as relates to my 7915 to
drop (actually raise) the voltage by 2V to -13VDC?

Each diode has a voltage drop and I just string 'em together to add up to
2VDC and tie them from the output of the 7915 to ground? I always figured a
diode was like a one-way resistor. Could I just use a resistor to ground to
get rid of some of my voltage? And, if so, how do I size it if I don't know
my current through the circuit? (I can't measure it, the transistor is
dead). Trial and error is a laborious process.

How can a diode RAISE the voltage of a 7912 (I'll dig around, might have one
somewhere)? Thanks a lot and pardon my ignorance.

Dave

Gord
Click to expand...
 
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