Toshiba TV29C90 problem; Image fades to black...

High B+ regulation in standby.
The margin for error is very small on the hv in the splitter.
As the capacitors fail in the power supply, the standby voltage will
drift over time up to as high as 165V, versus the 140~145V that is
suppose to be there.
Since that is a 15% increase in initial B+ at start up, which is beyond
the 10% margin for the insulation in the hv block, the hv is too high
initially at start up and this starts internal arcing at start up.
Over time these carbon tracks finally cascade and the hard carbon arc
short is started. The problem arises in that the regulator kicks into
run mode in about one second after turn on. The regulator is then
running off the horizontal feedback pulses for regulation. Since this
happens so fast and is only slightly above the x-ray trip voltage, the
x-ray circuit never triggers. Each turn on with standby B+ running
high will cause an arc over. The big problem we found was that if the
smps was not repaired and was the cause of the failure, it most times
would take 6 to 9 months before we would get a call back on the set
being dead. So shop policy had to be verify the smps secondary
voltages on ALL ctc169 sets, cr4118 and cr4116 must be in proper range
and clean looking on the o'scope. Extra 5 minutes of work to guarantee
no future problems.

The cr4118 failure can also cause the B+ to run high as it starts to go
leaky and fail. However I have never seen it fail to the point that
the B+ will run over 150V before the 15V line was too low for the set
to attempt to start up.

It is mainly the 2.2uF capacitor on the standby feedback line of the
smps that goes open that causes this problem. It is a simple matter to
measure the standby B+ voltage on the cathode of cr4116 with the tv
turned off to verify that there is not a problem.

 

[Mark D. Zacharias]

"MaxVT" <maxvt1@gmail.com> wrote in message
news:1120916082.848659.148260@f14g2000cwb.googlegroups.com...

Hello,

Does anyone possess a user or service manual or schematic of the subj.?

Thanks,

Max

I was able to get a PDF of a TA-AX295 which is upposedly the same or
similar. It's about a 6.4 meg PDF. Can you take an attachment of that size?

You may reply to:

mzacharias@labolgcbs.net

and reverse the domain name.

Mark Z.

 

"it turns crazy ?"
"it doesn't work ?"
...... Can you be a little more specific with a better (technical)
discription of the fault(s).
Exactly what codes do you think you need to "fix" the vcr ?
electricitym

 

[Dave Moore]

If it has any black Nichicon caps with the + on the top
or black Rubicon caps with the K on the top, they'll
probably all have to be replaced as they were
made with bad Chinese electrolyte and will leak
and damage adjacent components and copper
traces.

I'm going to compile a list of the the specific
"type" markings on these caps and post them
later.
Perhaps someone has already done this ?, dunno.

Dave

"MD" <I@hate.spam> wrote in message news:42cd5a35$0$2227$a726171b@news.hal-pc.org...
: I have a Mitsubishi VS-60803 CRT Rear Projection HDTV unit. It has this
: problem where when it powers on, the green power light flashes on, then
: shuts off half a second later. No image appears on the screen. There are
: also four evenly spaced clicking sounds: the first two coincide with the
: flashing, and along with the third, there is a quick, high-pitched whining
: sound. The clicking is coming from the vicinity of the flyback
: transformer.
:
: I've opened up the back and made a cursory check, seeing no burned or melted
: parts. What further steps can I take to isolate the problem? Would it
: likely be as simple as replacing the FBT?
:
: Thanks

 

[Dave Moore]

FWIW, I've seen the legendary ' bad toshiba vertical caps'
be either green or brown also


"Rono" <rono@nl.rogers.com> wrote in message news:FKednUcHKcCJh1LfRVn-1Q@rogers.com...
: Check, & replace capacitors near the IC,
: also replace any red caps by the jungle IC,
: & vertical IC. Rono.
:
:

 

[Dave Moore]

<metrix007@yahoo.com> wrote in message news:1120912581.146680.107280@o13g2000cwo.googlegroups.com...
:
:
: Art wrote:
: > Having opened the case and subjecting the platters and heads to nominal
: > atmospheric contaminates will probably render any recovery highly
: > improbable. This is one of the last things you want to do, maybe just to
: > harvest the nice magnets from the inside or if you like the see the mirror
: > finishes on the platters. At this point you are basically FUBARD as far a
: > recovery is concerned.
: > <ceraboy@yahoo.com> wrote in message
: > news:1120873485.440330.16560@o13g2000cwo.googlegroups.com...
: > > You can get the data recovered for several hundred dollars, but it may
: > > take a bit of time to send it in and you are not guaranteed the data
: > > will be recovered in which you still pay the money. You have to ask
: > > yourself, is the data really worth a backup. The fact that you opened
: > > the hermetic case in a non-clean room environment lessens the ability
: > > to recover the data at all and some houses may not even accept the
: > > drive.
: > >
: > > http://www.gillware.com/?campaign=google3
: > >
:
: It would be nice to have my data back, but its not crucial in any way..
:
: My expertise is in computer forensics, if there was any way to get a
: bios to recognise my harddrive, I could then recover what i need, as
: the two files I am after are each less than 25kb in size. Is it
: possible at all to repair or replace the arm and heads, or transfer the
: platters to a different drive?
:
: Thanks


If BIOS won't detect the drive, probably the circuit board
on the drive was defective and there probably wasn't any good
reason to open the HDA assembly.

You could probably buy an identical drive off Ebay just to get
the HDA controller PCB off of it to replace the bad one
on the defective drive.



:

 

[Dave Moore]

I ordered an Aopen MB from MCM awhile back
and even though the packaging had never been opened
before, all of the caps on the motherboard were
swollen.

I was unab'e to find any evidence of prior use and
concluded that the caps went bad from the board simply
sitting on the shelf in a warehouse somewhere.

MCM offered to send me a replacement, but
I figured they'd just send me another board with the same
problem so instead I just kept the board and replaced
all of the caps with hopefully superiorPanasonic
caps from Digkey

Fortunately the board worked and in fact, I just
typed this post on it


"JW" <none@dev.nul> wrote in message news:nppnc1da2fs5kvu13ud0puehh73esgkg5v@4ax.com...
: Just a heads up on Electrolytic Capacitor Leakage on some 875 & 865 based
: products.
:
: http://www.intel.com/cd/channel/reseller/asmo-na/eng/tech_reference/box_desktop/int_inst_info/dsk_factory_notes/193414.htm
:
: Products Affected:
:
: IntelŽ Desktop Boards
: D865GBF, D875BZL, D865GLC, D845EPI, D865PERC, D865GRH, D865PERL, D845GVSR,
: D865PESO, D845GLVA, D865GWV, and IntelŽ Entry Server Board S875WP1-E.

 

[Leonard Caillouet]

Interesting. I never noticed the standby B+ going that high. I'll have to
check more closely. We have several routine checks on the 169 chassis on
any set that comes in that includes the caps in the power supply so the get
changed if they are bad. I often don't check the standby B+ until after the
repair is done so I had not noticed that. We do, however, change lots of HV
dividers in sets where the PS caps are fine. In those cases the B+ is
checked and I have not seen it out of range. I guess the small margin of
safety on the divider is the problem. I have also changed quite a few that
were dne by other shops previously and the grommets were missing or the lead
was not inserted correctly. So the OP should be careful to install it
correctly or be prepared to change it again before long.

You wold think that they would not start the horizontal osc. until B+ is
regulated. But then, you would think a critical part like a high voltage
splitter would be built with a greater safety factor.

Thanks, David.

Leonard

<dkuhajda@locl.net> wrote in message
news:1120957767.594663.21340@g14g2000cwa.googlegroups.com...

High B+ regulation in standby.
The margin for error is very small on the hv in the splitter.
As the capacitors fail in the power supply, the standby voltage will
drift over time up to as high as 165V, versus the 140~145V that is
suppose to be there.
Since that is a 15% increase in initial B+ at start up, which is beyond
the 10% margin for the insulation in the hv block, the hv is too high
initially at start up and this starts internal arcing at start up.
Over time these carbon tracks finally cascade and the hard carbon arc
short is started. The problem arises in that the regulator kicks into
run mode in about one second after turn on. The regulator is then
running off the horizontal feedback pulses for regulation. Since this
happens so fast and is only slightly above the x-ray trip voltage, the
x-ray circuit never triggers. Each turn on with standby B+ running
high will cause an arc over. The big problem we found was that if the
smps was not repaired and was the cause of the failure, it most times
would take 6 to 9 months before we would get a call back on the set
being dead. So shop policy had to be verify the smps secondary
voltages on ALL ctc169 sets, cr4118 and cr4116 must be in proper range
and clean looking on the o'scope. Extra 5 minutes of work to guarantee
no future problems.

The cr4118 failure can also cause the B+ to run high as it starts to go
leaky and fail. However I have never seen it fail to the point that
the B+ will run over 150V before the 15V line was too low for the set
to attempt to start up.

It is mainly the 2.2uF capacitor on the standby feedback line of the
smps that goes open that causes this problem. It is a simple matter to
measure the standby B+ voltage on the cathode of cr4116 with the tv
turned off to verify that there is not a problem.

 

[Art]

I have noticed a few of these chassis having the increased standy B+ and
have serviced the chopper, regulator circuit before returning then to
service. It is an interesting question tho, did the HV block fail because of
the increased B+ or is it just co-incidence? Due to the age of these sets
the caps are going bad anyway and need replacing. Good point David!
"Leonard Caillouet" <lcaillonospam@devoynet.com> wrote in message
news:BR6Ae.31654$up5.29048@lakeread02...

Interesting. I never noticed the standby B+ going that high. I'll have
to check more closely. We have several routine checks on the 169 chassis
on any set that comes in that includes the caps in the power supply so the
get changed if they are bad. I often don't check the standby B+ until
after the repair is done so I had not noticed that. We do, however,
change lots of HV dividers in sets where the PS caps are fine. In those
cases the B+ is checked and I have not seen it out of range. I guess the
small margin of safety on the divider is the problem. I have also changed
quite a few that were dne by other shops previously and the grommets were
missing or the lead was not inserted correctly. So the OP should be
careful to install it correctly or be prepared to change it again before
long.

You wold think that they would not start the horizontal osc. until B+ is
regulated. But then, you would think a critical part like a high voltage
splitter would be built with a greater safety factor.

Thanks, David.

Leonard

dkuhajda@locl.net> wrote in message
news:1120957767.594663.21340@g14g2000cwa.googlegroups.com...
High B+ regulation in standby.
The margin for error is very small on the hv in the splitter.
As the capacitors fail in the power supply, the standby voltage will
drift over time up to as high as 165V, versus the 140~145V that is
suppose to be there.
Since that is a 15% increase in initial B+ at start up, which is beyond
the 10% margin for the insulation in the hv block, the hv is too high
initially at start up and this starts internal arcing at start up.
Over time these carbon tracks finally cascade and the hard carbon arc
short is started. The problem arises in that the regulator kicks into
run mode in about one second after turn on. The regulator is then
running off the horizontal feedback pulses for regulation. Since this
happens so fast and is only slightly above the x-ray trip voltage, the
x-ray circuit never triggers. Each turn on with standby B+ running
high will cause an arc over. The big problem we found was that if the
smps was not repaired and was the cause of the failure, it most times
would take 6 to 9 months before we would get a call back on the set
being dead. So shop policy had to be verify the smps secondary
voltages on ALL ctc169 sets, cr4118 and cr4116 must be in proper range
and clean looking on the o'scope. Extra 5 minutes of work to guarantee
no future problems.

The cr4118 failure can also cause the B+ to run high as it starts to go
leaky and fail. However I have never seen it fail to the point that
the B+ will run over 150V before the 15V line was too low for the set
to attempt to start up.

It is mainly the 2.2uF capacitor on the standby feedback line of the
smps that goes open that causes this problem. It is a simple matter to
measure the standby B+ voltage on the cathode of cr4116 with the tv
turned off to verify that there is not a problem.

 

If any one knows the model number of the remote, then I could look for
one on ebay.

 

Coincidence due to age? Maybe. What I find mostly is the cap will be
marginal. After the set is plugged in a while it all warms up and the
B+ seems to be close enough to the ideal 143V. But when the set is
cold, the B+ is higher. Typical bad capacitor problem.

A 10% increase in B+ on start up is a 10% increase in HV, 28,000 volts
is quite a lot less than 30,800 volts.

They do have the unit regulating at start up. The standby rough
regulator feedback is doing the regulating, when it fails to regulate
on the money, there is nothing that will keep the set from coming on,
until it goes so high that there is a catastophic failure.

So as always, check/replace the capacitors in the smps and cr4118
everytime.

 

[dfwjas]

The sony service rep came by and concluded that the remote related
circuit inside the TV is bad & needs to be replaced. He mentioned that
the cost of replacing the circuit would be $500 + labor. I am not sure
that this is the right diagnosis of the problem as he did not even open
the TV to check the circuit, all he did was tried using a different
remote with the TV - which I had done in the past.

BTW he offered to buy the TV from me for $200 which I refused - what a
scam

At this point I have decided to leave the TV as-is & use it without the
remote. What do you folks think?

dfw

 

[MaxVT]

Thanks for all input, everyone! Now, the saga continues...

I've checked the transformer: one winding produces +19.2v, -19.2v and
(I assume) ground, the other produces 10v and ground.

Continuing to main board, there is a diode bridge and from there 3
regulators: 5v standby, and +15v / -15v controlled with a relay.

A relatively big resistor immediately before the input to 5v regulator
is cracked and the solder has evaporated from its connection. Also,
there is a leaked cap in the -15v circuit.

I can replace the resistor and the cap, however how can I check that
the regulators (7805C, 7815C, 7915C) are OK and the load is not
excessive, so as not to create any additional leaks and explosions?

BTW, I do have electronics knowledge (B.Sc in EE), however zero repair
experience... One has to start somewhere

Thanks,

MaxVT

 

[James Sweet]

I can replace the resistor and the cap, however how can I check that
the regulators (7805C, 7815C, 7915C) are OK and the load is not
excessive, so as not to create any additional leaks and explosions?

Check with a multimeter that they're not shorted, otherwise they have
internal overload protection so you can apply power and measure the output
voltages.

 

[James Sweet]

If BIOS won't detect the drive, probably the circuit board
on the drive was defective and there probably wasn't any good
reason to open the HDA assembly.

You could probably buy an identical drive off Ebay just to get
the HDA controller PCB off of it to replace the bad one
on the defective drive.

This does sometimes work, though the newer the drive, the less likely it is.
I ran a Conner 1.2 gig drive for several years after a board swap.

Opening it was definitly a bad idea, but so long as the platters have not
been touched or anything fooled with inside it then it may still read fine
for a while.

 

[Michael Kennedy]

That's what I thought to start with to start with also. But I found that it
could be activated with an IR diode. I have isolated the spot. It is a
testpoint that leads to a chip on the other side. The testpoint is a small
hole.

I don't know what or why it works, but I wired an IR diode in and volia. The
button is functioning how it should, except you can't do a master reset with
it.

My theory on why it is working is that there is a crack in the chip on the
other side. But since I know nothing about how chips work I don't know if
that is a possible cause.

- Mike

"Not me" <nobody@anywhere.com> wrote in message
news:ff20d11c8s4apah7rapo8nmqv7e0fh4kfb@4ax.com...

On Fri, 8 Jul 2005 02:19:48 -0400, "Michael Kennedy"
Mikek400@nearthlink.net> wrote:

Hi, I bought an ipod with a broken menu button. Well i thoght I'd just
have
to resolder or buy a new switch.. I resoldered the switch with no luck and
then I checked it with an ohm meter and it checked good. Now here is the
Weird part, I was inspecting the board under my desk lamp with it powered
on
and the switch started working, well sort of.

If you shine light on part of the board it closes the circut like you
pushed
the button down!!!??? There is not an optical sensor that i can see
anywhere near there, and it is away from the switch that doesn't work. It
has some smt resistors in the area and some holes that appear to go all
the
way through to a chip on the other side.

So my question is what the heck is going on??? I've never seen anything
like
this before. It is not supposed to be light activated..

I'll put some picures up on my web server when I find my digital camera
charger.

- Mike


How close are you getting with the light? Could you be causing some
sort of thermal effect?

 

[Michael Kennedy]

It won't ask for memory. You have to have memory in the pc for it to do
anything but beep. That's all you'll get without memory BEEEP BEEEP
BEEEP.... If you take everything out except the processor it should
beep..(including memory and vid card) Beeping a good sign and and means the
bios is working.

- Mike

"James Sweet" <jamessweet@hotmail.com> wrote in message
news:Zmlze.14689$Yb4.6535@trnddc08...

"jakdedert" <jdedert@bellsouth.net> wrote in message
news7lze.40466$qm.19724@bignews5.bellsouth.net...

"Choreboy" <choreboyREMOVE@localnet.com> wrote in message
news:42CDDAFF.AC1C4CA5@localnet.com...
Neighbors have a computer that won't work after a lightning strike.
With the video cable connected, the monitor stays black and in the
standby mode. There are howls from the speakers, like feedback. With
the cable disconnected, the monitor will briefly show a notice that
it's
not connected. There are no howls from the speakers although the mic
cable remains connected.

With the power off, I checked the pins of the monitor cable to see that
the grounding pins were grounded and the signal pins were not. One
grounding pin is open, so it seems certain that the monitor is damaged.

The next step would be to try another monitor to see if there's other
damage to the system. In case the computer's video card is damaged,
can
a monitor be damaged by plugging in to it?

'Probably' not, but why not try plugging their monitor into your
computer?
That's extremely unlikely to cause any damage. Then, I'd take
*everything*
out of the neighbor's computer, except the vid card...unplug memory, all
drives including floppy...just leave in the CPU and vid card.



Actually I'd be more concerned about that causing damage than the other
way
around, but realistically either way should be fine.

 

[kip]

Best get those prices under control because us Tech,s do not pay those
prices.

kip
"DBLEXPOSURE" <celstuff@hotmail.com> wrote in message
news:aYCdnR55Yct3EEzfRVn-uQ@rapidnet.com...

New electronics parts and supplies store. Discrete components, shop
supplies, parts and more.

Somewhat still under construction but many items available


http://e-parts.netfirms.com/

 

[kip]

Did you tell him your name was Tucker NOT Sucker.

kip
"dfwjas" <dfwjas@gmail.com> wrote in message
news:1121013026.935499.228370@z14g2000cwz.googlegroups.com...

The sony service rep came by and concluded that the remote related
circuit inside the TV is bad & needs to be replaced. He mentioned that
the cost of replacing the circuit would be $500 + labor. I am not sure
that this is the right diagnosis of the problem as he did not even open
the TV to check the circuit, all he did was tried using a different
remote with the TV - which I had done in the past.

BTW he offered to buy the TV from me for $200 which I refused - what a
scam

At this point I have decided to leave the TV as-is & use it without the
remote. What do you folks think?

dfw

 

[Hugh Prescott]

If your area of interest is computer forensics then you have rendered the
forensic data on the drive null and void. Data recovery is now an extreamly
remote possibility.

Had the drive not been opened it would normally be possible to have a data
recovery house repair the drive and recover the data to a CD.

Last drive recovery for a client was a failed Novell data drive due to a
single head going open. Drive repair was something like $50, data recovery
to a CD was $1,600.

And never trust a drive after a failure, It's not worth it.

And yes I have poped the top on drives with striction and got them spinning
without a clean room. Quick burn to a CD and install a new drive. Sometimes
you are luck, mostly not.

Hugh



<metrix007@yahoo.com> wrote in message
news:1120912581.146680.107280@o13g2000cwo.googlegroups.com...

Art wrote:
Having opened the case and subjecting the platters and heads to nominal
atmospheric contaminates will probably render any recovery highly
improbable. This is one of the last things you want to do, maybe just to
harvest the nice magnets from the inside or if you like the see the
mirror
finishes on the platters. At this point you are basically FUBARD as far
a
recovery is concerned.
ceraboy@yahoo.com> wrote in message
news:1120873485.440330.16560@o13g2000cwo.googlegroups.com...
You can get the data recovered for several hundred dollars, but it may
take a bit of time to send it in and you are not guaranteed the data
will be recovered in which you still pay the money. You have to ask
yourself, is the data really worth a backup. The fact that you opened
the hermetic case in a non-clean room environment lessens the ability
to recover the data at all and some houses may not even accept the
drive.

http://www.gillware.com/?campaign=google3


It would be nice to have my data back, but its not crucial in any way..

My expertise is in computer forensics, if there was any way to get a
bios to recognise my harddrive, I could then recover what i need, as
the two files I am after are each less than 25kb in size. Is it
possible at all to repair or replace the arm and heads, or transfer the
platters to a different drive?

Thanks