Toshiba TV29C90 problem; Image fades to black...

Chassis ?

 

[simon hanlon]

Model number 284248WNS
chassis Beko 14.2 I think
<intiglietta@email.it> wrote in message
news:1137007748.712014.187380@z14g2000cwz.googlegroups.com...

Chassis ?

 

Read your emails

 

You have to find the Service Manual, waveforms are different from model
to model

Inty

 

Er..... the RF cable is a coaxial, 75 ohm type cable.

 

[Asimov]

"tekamn" bravely wrote to "All" (11 Jan 06 04:02:46)
--- on the heady topic of "Re: Favorite Tektronix Scope"

te> From: "tekamn" <and7@bigfoot.com>
te> Xref: core-easynews sci.electronics.repair:354813


te> Agreed. No component level repair, no schematics. Custom ordered smps
te> power supplies.

te> The power supplies have sometimes nasty field failures. I remmeber a
te> few TDS3xx series scopes I had to repair. Always a burned out start-up
te> resistor to replace. Hard to discover, but after doing this once:
te> repair of the othe scopes was quickly to be done ;-)


About switching supply start-up resistors, they typically get zapped
by powerline transients. The voltage rating is often inadequate for
these. One idea is to use 2 in series to increase the rating and to
mount them physically standing off the pcb a couple of body thickness,
to distribute the transient more evenly across the length. There is
always a little witch doctor stuff in some equipment. I like the
"works with the cover off", so puts a pix of serviceman inside.

A*s*i*m*o*v

.... Over a hundred billion electrons were used in crafting this tagline.

 

[mc]

About switching supply start-up resistors, they typically get zapped
by powerline transients. The voltage rating is often inadequate for
these.

Tell me more. How do I recognize startup resistors? What is their position
in the circuit?

 

[dkuhajda@locl.net]

The fault was never repaired. ESR or jump out the vertical circuit
capacitors. As the new ic has completely failed by now, you also need
to replace the vertical output ic and probably a fusible resistor.

 

[b]

floss ha escrito:

Hi B,
Well, I tried your suggestions... I've made progress but I'm not there yet.

Don't worry! we'll keep at it.

When I first connected everything up, I had no picture or sound on my TV.

1. Assuming you connected everything up as I mentioned, to the letter,
then that is probably just a case of tuning the tv into the dvdvr. Did
you play something recognizable and start the tuning sequence? you
ought to be able to get that signal. try putting the tv onto an unused
programme number (say 7), and try again.....

I then added the scart lead from my VCR port on the freeview box to
the scart on the TV. This gave me all the channels on freeview through
channel E1 on my TV.

.....but that means you won't get them 'through' the dvdr and hence
can't record them.

2. If there are 2 scarts on the dvdr, Try connecting the OUT /tv one to
the tv's scart.
You should then get the dvd-r on E1 on your tv.

3. connect freeview's 'vcr' scart to the dvdr's IN scart. To get
freeview, select Av or Ext or whatever ON THE DVD-R.

However the AV channel remains blank.

....what machine are you referring to??
AV is usually the same as E1 . both names usually refer to 'whatever is
coming in via the scart socket'. ( Unless AV on your set is a tv
programme position (often also called 0) which is not connected to
scart, you have to tune it in to something but lets not worry about
that for the moment..)

When I

switch on the DVDR it plays the DVD but there is nothing playing on the
screen. I retuned my TV to see if it picks up the DVD but it did not.

Did you get a menu or ANYTHING from the dvdr? (in any case, if you did
what i mentioned in 2. above this ought not to matter now, it should
be on tv's E1)

I
was also able to 'record' from the scart channel on the DVD but I am
unable to play whats recorded, just like the ordinary DVD.

I dont understand. If you can record but not see anything on the tv
screen from the dvdr, how do you know if it really is recording from
scart?

anyway try the above and post back!
regards,
B

 

[Jim Yanik]

"Asimov" <Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote in
news:MSGID_1=3a167=2f133.0_43c55d18@fidonet.org:

"tekamn" bravely wrote to "All" (11 Jan 06 04:02:46)
--- on the heady topic of "Re: Favorite Tektronix Scope"

te> From: "tekamn" <and7@bigfoot.com
te> Xref: core-easynews sci.electronics.repair:354813


te> Agreed. No component level repair, no schematics. Custom ordered
smps te> power supplies.

te> The power supplies have sometimes nasty field failures. I
remmeber a te> few TDS3xx series scopes I had to repair. Always a
burned out start-up te> resistor to replace. Hard to discover, but
after doing this once: te> repair of the othe scopes was quickly to
be done ;-)


About switching supply start-up resistors, they typically get zapped
by powerline transients. The voltage rating is often inadequate for
these. One idea is to use 2 in series to increase the rating and to
mount them physically standing off the pcb a couple of body thickness,
to distribute the transient more evenly across the length. There is
always a little witch doctor stuff in some equipment. I like the
"works with the cover off", so puts a pix of serviceman inside.

A*s*i*m*o*v

... Over a hundred billion electrons were used in crafting this
tagline.

I believe the stand-off and use of multiple resistors is to dissipate heat
better,not for "transient protection".(at least that is why TEK did it.)
The transient is probably the surge that blows the weakened part,like a
incandescent lamp's filament.

Lots of TEK stuff had problems with metal film resistors,and not just in
power supplies.
Also problems with carbon film resistors,in HV focus circuits.

--
Jim Yanik
jyanik
at
kua.net

 

[Jim Yanik]

"mc" <look@www.ai.uga.edu.for.address> wrote in
news:fEfxf.34002$0y2.19442@bignews2.bellsouth.net:

About switching supply start-up resistors, they typically get zapped
by powerline transients. The voltage rating is often inadequate for
these.

Tell me more. How do I recognize startup resistors? What is their
position in the circuit?

They charge up a PWM IC's housekeeping supply capacitor before the supply
actually begins switching.
Generally directly from the rectified line V,and there might be a xfmr
winding and diode to take over once switching has begun.(usually,in TEK
supplies)

--
Jim Yanik
jyanik
at
kua.net

 

[mc]

Tell me more. How do I recognize startup resistors? What is their
position in the circuit?

They charge up a PWM IC's housekeeping supply capacitor before the supply
actually begins switching.
Generally directly from the rectified line V,and there might be a xfmr
winding and diode to take over once switching has begun.(usually,in TEK
supplies)

What sort of resistances and wattages are we looking for?

 

[Jim Yanik]

"mc" <look@www.ai.uga.edu.for.address> wrote in
news:1Xhxf.117904$k76.74558@bignews6.bellsouth.net:

Tell me more. How do I recognize startup resistors? What is their
position in the circuit?

They charge up a PWM IC's housekeeping supply capacitor before the
supply actually begins switching.
Generally directly from the rectified line V,and there might be a
xfmr winding and diode to take over once switching has
begun.(usually,in TEK supplies)

What sort of resistances and wattages are we looking for?

It depends.Some TEK supplies used 0.5w carbon film resistors,some used 1W
carbon film,replaced under mods by carbon comp resistors for longer life.I
can't recall specific R values.Some used two R's in series,some 2 in
parallel.
The 2215 pre-reg schematic I have shows a single 150K 1W res.

R Values also depend on the housekeeping cap's value.You want the HK cap to
charge slow enough that the line caps reach full V before the PWM IC
starts.

--
Jim Yanik
jyanik
at
kua.net

 

[James Sweet]

Goldenshuttle wrote:

Hi Guys
If we add a bridge rectifier to the output of light Dimmer to make a DC
motor control.....would it work ? did any of U pals try it ???

What's the voltage and current of the motor involved?

It might work, but it's certainly far less than ideal. You'd be much
better off to control power to the motor with a mosfet switched by a 555
configured as a variable duty cycle oscillator.

 

[James Sweet]

mc wrote:

About switching supply start-up resistors, they typically get zapped
by powerline transients. The voltage rating is often inadequate for
these.


Tell me more. How do I recognize startup resistors? What is their position
in the circuit?

Do some reading about switchmode power supplies, there's lots of generic
info out there that will help.

 

[Erich Schultheis, the man]

Harry Hamilton wrote:

"CLFan" <clfan@easy.com> wrote in news:1137022766.000801.245290
@g47g2000cwa.googlegroups.com:

You've made a good first impression. The chick likes you. You like her.
She's pretty. You have a pleasant conversation. She touches you a
little bit. She smiles. She looks away shyly when you look into her
eyes. She touches you some more.
She likes you.
You get excited. Maybe you have a real chance with this chick. Finally.
After all those years. Maybe the best chance you've ever had. Don't
even think about messing this up. She's pretty. No, this time you're
not going to mess this up. She's friendly. This time you'll play it
exactly the right way. She's just right for you. You shouldn't mess
this up. Imagine what it would be like to introduce her to your
friends. Or to finally show your parents that you're not gay after all.
You really shouldn't mess this up. She likes you. Maybe she has a crush
on you. She may be deeply in love with you. If you don't mess this up,
you might get married to her. You might have kids with her. She's in
your future. She'll be there when you die. If you don't mess this up.

But you mess up.

And the chick turns out to have a life of her own. She has a future in
which you play no part. You're just another of those guys she was
remotely interested in some time ago.

And you're back to where you always were: insignifcance.


I think once or twice.

Drop dead you son of a bitch. Your name isn't Harry Hamilton and
Beatrice is your daughter.

 

[Shoreline Electronics]

Change these caps and the IC again ( My notes show that IC is a LA7836 NOT a
7838)

C451 220/16v
C455 100/35v


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

"TGK" <tg_kua@yahoo.com> wrote in message
news:bf28158491bcc9ed83134619c21ac80d@localhost.talkaboutelectronicequipment.com...

TV Started few months ago with extra ghosting hor.line on top 10% of
screen. Then losses screen. Resoldered most joint, replaced LA7838 vert
IC. TV back to condition before with a couple of horizontal line on top of
screen. 2 days later returned to no screen with sound/ channel ok.
How do I fix the root cause - the extra horizontal line appears on top
section of screen? OR could it be something else?
Thank you!

 

[Shoreline Electronics]

Yes , The cap mod works perfect.


--
==========================
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:1136950741.800073.116180@g47g2000cwa.googlegroups.com...

Calling RCA Tech line...the main Tech taking care of most of
Canada...out of the office
till Jan 17 2006. Average phone call to the specified number...ten
minute wait....got nobody
to come to the phone! Surprise, surprise!

Got an E-Mail back from a Broadcast Station with a link. Look here:

http://www.yorkdispatch.com/local/ci_3388746

Not sure of the exact repair used. Has anyone done this: Try putting a
1uf
electrolytic capacitor @ 50vdc from pin 15 of U3101 to ground (+ to pin
15).
This mod will also defeat (kill) closed caption.

Nobody anywhere is taking the blame, or doing an actual repair, on this
huge problem, from
what I can find. Cable companies saying, not ther fault. The units I
have seen since the new
year, work fine for days, after being unplugged, & broght in for
service. Anyone have a plan?

Here's what I have so far! Excuse me if some info is there twice.
RCA no sound issue.

http://wa6ati.com/CTC195-197.html

http://philips.nl/assets/Downloadablefile/Whitepaper_GUIDE-Plus+-3312.pdf

http://64.233.161.104/search?q=cachezNHusvoizUJ:218.20.188.180/SER/H03-ICTVP514680-3/H03-ICTVP514680_IC-0915-04-07WT.pdf++a+VBI+inserter+used+in+gemstar+modules&hl=en

if you do a control F and search for guide you will come across the
Guide Plus info.
It is a little difficult to read but what I get out of it is that of
the 5 tests shown, the first
2 should definitely pass ( rom and ram ) the 3rd test will pass if you
have VBI packets
coming in ( mine only passes when I run the diag from channel 47 ABC )
the last 2 tests are for communication between your TV and other
devices.
in the diagnostic, you can push the numbers 1,2,3,4,5 to rerun the
individual tests without going throught the whole sequence again.

We have confirmed that guideplus have made changes in their system
causing this issue. "Stack overflow" error in the television's

Shaw has not made changes to how this information is delivered but are
working with guideplus to have them correct the issue.

This trouble is caused by a defective data packet broadcast from a
local TV station. The data packet is located in
the VBI (Vertical Retrace Interval). It's purpose is for XDS (Extended
Data Services) that is used by the GemStar
circuitry. The condition is very intermittent and not much is known to
the average TV technician because Thomson
is not releasing much information to the public other than removing
the power and reapplying it again. Thomson's
answer to this issue is taking their case to the FCC and let them
resolve the conflict between FCC and the
broadcasters. This phenomena only effects certain Thomson chassis
CTC197, CTC195 and CTC203. Only a
specific run of serial numbers are also effected. As of this date
7-12-2001 there is no cure offered by Thomson.
Yes unplug, wait then plug is only solution for this GEMSTAR lockups.
The Gemstar is part of one CPU module that thomson unwisely used
instead of using seperate ICs, one for TV microcontroller, gemstar get
their own. JVC, and others are using seperate modules and not always
present so this is less common than Thomson (RCA & GE TVs) units.
Recent basic thomson units don't have Gemstar for last couple years.

There is no fix for this. The fault lies with the broadcaster who
maintains the equipments that send outs data on line 21 be careful and
up to date.

We had one happen recently, had to haul the Thomson TV back to
customer's. Jack waited not long enough for the micro to "lose power &
forget".

Not true! There is a fix! But this fix will disable CC functions. Read
on!

RCA CTC197 & CTC195 & CTC203

# THOMSON AUDIO DROP-OUT NUISANCE FIX
There has been a situation when in some RCA/GE televisions a low-level,
scratchy-sounding noise comes out of the speakers instead of normal
audio,
or when video is muted. These problems can occur when invalid XDS data
is
broadcast by television stations and received by certain Thomson
television
receivers. XDS data is digital information placed within the video
signal's
vertical interval of an analog (NTSC) television transmission. This
data
is
used by the microprocessor in the television receiver. It may be
transmitted
from any analog television channel.
A fix that I have been recommending to our techs is to place a 1uf 50V
capacitor to ground on U13101(15). This swamps the closed caption data
to
the micro and stops the reception of the defective data packet. In the
event
that later on the resolve the defective data problem the capacitor can
be
removed. Obviously the closed caption feature will be crippled with
this
capacitor installed.

This has been a topic of conversion most of the day....Try putting a
1uf
el.cap @ 50vdc from pin 15 of U3101 to ground (+ to pin 15).
This mod will also defeat (kill) closed caption.
I kept hearing this mod with result of disabling CC as side effect,
and I didn't hear of that like this from RCA's modification data. By
the way, I find this UNACCEPTABLE mod; since many users are hard of
hearing or deaf (I'm one of these) needs CC.
By the way, how often this problem crops up is not that often and I
bet there are so MANY similar gemstar modules in many units (CTC203,
195/197, ATC113 models and several more?
And the cable providers have the equipment and items that generate
data on 21th line, there was a period when there was a feature bug
that generated extra bits, but I assume is fixed and from what I see
they were very anxious to keep this thing very quiet. Only thing that
happens from time to time is glitch that can't be prevented that very
occasionally "crashes" these type of gemstar modules and needed a
unplugged for 30 minutes to a hour to "reboot" a TV back to normal.
By the way ITC008 no longer have gemstar support but I find it
cheapened a bit like it no longer can hold channels memorized.
Citizen IS cheaper than RCA ITC008 and did have that channel memory
stored on eeprom. That's not typical of Thomson's for this. CTC185
is the CHEAPEST chassis of all and did have the channel memorized in
eeprom.
Go to the Guide Plus Setup. Mark USA, then enter 00000 for the
zip code, answer "No", then answer "No". click through the rest of the
installation.

Then go back and enter everything including your zip. This is suppose
to "RESET"
the memory. Then turn the TV off for at least 12+ hours. Everything
should be back
TV Guide Plus
TV Guide Plus progrOK, I found it on a Tech site, Enter the guide setup
program. On my set it is Menu then Guide Plus. The next menu will show
setup at the top. At this point, press GOBack twice and then TV. This
resets the Gemstar module and goes into a Diagnostic. If you start this
sequence from the channel where you think your data is coming from, the
VBI packet info will show data coming in.

mming is carried on the local PBS affiliate,
Without a Cable box
Go thru the normal setup. When the TV is off it will find the TV Guide
signal and download the information.
With a Cable Box
When you set up the Guide Plus it will ask you if you have cable. If
you say yes, it will ask what brand the cable box is. This is important
when you want to use the TVs remote control, or the Guide Plus features
to control the cable box, but not necessary to acquire the Guide Plus
information.
Important: When the TV is off, leave the cable box tuned to the local
affiliate, that downloads the data.
Thomson representative on our direct RCA TV line at 1-800-336-1900
Monday - Friday 8 a.m. - 8 p.m. and Saturday -Sunday 10 a.m. - 7 p.m.
(EST).

turn off the tv while it's set at channel 3
Turn TV off and unplug for 5 minutes.
Plug in and turn back on.
Go through the TV setup and make sure you manually put in the time.
When you get to the GuidePlus setup, scroll over to the SCHEDULE
section and remove everything that is in there, if any. (A power outage
or unplugging the TV won't delete any scheduled programs.)
Go to setup and re-enter your zip code using the up and down buttons
rather than the number buttons. Click the OK button after you're
finished with GuidePlus setup. Turn the TV off without going back to
normal TV viewing. Within 2 hours the GuidePlus menu will show, but it
won't show any progrmas yet. It will list channels, but won't tell you
what is on.
Leave TV off for 12 hours.
Note: You can still watch TV without the channels being listed, but it
takes longer for the programs to show up. Usually after a period of off
time.

just talked to 1 800 336 1900. they told me to go to set up and put in
usa and then 99999 for my zip finish set up and shut down for 35-45
mins. and then do set up again with the right zip. shut down for 24
hrs. and then see if u have ur listings.
I kept hearing this mod with result of disabling CC as side effect,
and I didn't hear of that like this from RCA's modification data. By
the way, I find this UNACCEPTABLE mod; since many users are hard of
hearing or deaf (I'm one of these) needs CC.

By the way, how often this problem crops up is not that often and I
bet there are so MANY similar gemstar modules in many units (CTC203,
195/197, ATC113 models and several more?

Yes there are two types of CTC203 chassis, one is one ribbon with
smart chassis (has micro onboard), and other one that uses two ribbons
with dumb chassis (no micro on the chassis, the micro is built right
into gemstar).

The one ribbon you can unplug ribbon cable and remove gemstar module
entirely. The two ribbon type, you have only two options, manual
reset with remote or unplug and wait for half a hour.

Remember to ask customer first before doing the cap modification
because some use CC.
Guide Plus not working:
I asked the tech to enter the TV GUIDE plus set up mode and read me the
options in the set up dialogue. When the tech got to the part of the
set up that discussed "Do you have a VCR?" It had been selected and it
was available on Video 1 only. Unit has TV Guide set up incorrectly. I
had the tech enter an illegal zip code (99999) and tell the set up the
No DSS, no VCR, and No cable box is present. The illegal zip code will
cause a auto reset of the TV GUIDE Plus module and will remove it's
hold on the chassis tuner. This corrected the problem. Now the tech
will need to reset up the TV GUIDE PLUS correctly
I had tech reset the TV guide module by entering the Guide plus setup
program the hitting the "Go back" button on the remote then hit the
"TV" button twice. This clears the old data in the system and starts a
internal test program. It will check the ROM, RAM, VBI, and G-LINK. All
passed except the VBI and Glink. The VBI did not pass because it was
not on the host channel. The Glink did not pass possibly because the
Glink cable is defective or a bad IR blaster at the end of the G-link
cable. The G-link is necessary for VCR programming because the
television will turn on the VCR via the G-link cable and IR blaster,
make the VCR select the channel, and place it in the record mode.
Apparently the TV guide plus module was connected incorrectly. The
connector J23905 was connected to the front video line input. There
does not appear to be any cable from J23905 to J26401. Tech will need
to hard wire a jumper from J23905(1) to J26401(2) J23905(2) to
J26401(1) Note: these are opposite from each

 

[floss]

b Wrote:

1. Assuming you connected everything up as I mentioned, to the letter,
then that is probably just a case of tuning the tv into the dvdvr. Did
you play something recognizable and start the tuning sequence? you
ought to be able to get that signal. try putting the tv onto an unused
programme number (say 7), and try again.....
2. If there are 2 scarts on the dvdr, Try connecting the OUT /tv one
to
the tv's scart.
You should then get the dvd-r on E1 on your tv.
3. connect freeview's 'vcr' scart to the dvdr's IN scart. To get
freeview, select Av or Ext or whatever ON THE DVD-R.
AV is usually the same as E1 . both names usually refer to 'whatever
is
coming in via the scart socket'. ( Unless AV on your set is a tv
programme position (often also called 0) which is not connected to
scart, you have to tune it in to something but lets not worry about
that for the moment..)
Did you get a menu or ANYTHING from the dvdr? (in any case, if you did
what i mentioned in 2. above this ought not to matter now, it should
be on tv's E1)
anyway try the above and post back!
regards,
B

Hi B

Thanks once again for your speedy reply. Again, progress has been made
but not quite there yet. Here goes!
I connected the DVD OUT to the TV scart, and the freeview 'vcr' scart
to DVD IN scart and arranged the RF cables as you said. Hey presto as
predicted I got the freeview channels on E1. With the cables arranged
like this I was able to record and play discs and also play
pre-recorded discs with no problems. Success! But the picture on the TV
(and subsequently on the recorded disc) is so poor its not worth
watching!! It is very blurry and black and white.I checked the settings
for the TV and freeview were configured to scart and they are. I tried
changing the TV reception from NTSC to PAL but this made no difference.
I tried tuning the TV, but I'm not entirely sure I'm following your
suggestions correctly there, as I used the autoscan to look for
channels. Anyway the scan only picked up the analogue channels. The DVD
has a channel scan, I ran this too, but it came up with zilch. No
channels found.
You mentioned before that AV can be a TV programme position... I
pressed zero on my remote, and AV channel popped up on the TV screen,
so what does this mean?? Does this change things?

Kindest regards,
floss.


--
floss

 

[Charon]

The retrace lines are all white, so it should be comming from all of
the crt's. The model is Hitachi CT4532, I have a pdf service manual for
it. And can make this available to anyone interested.
www.bauld.com/~eric/ct4532.zip

B+ was at 111 V Should be 110
Unsure of the crt voltage, or how to test that yet.

I am trying to get my hands on a ocsilloscope for further tests.

Im rather new to electronics repair, so I learn as much as I can as I
go. I have wanted to do electronics repair for some time as a hobby. I
have been reading, reading and more reading but know far from
everything