Toshiba TV29C90 problem; Image fades to black...

[Michael Kennedy]

"Chrisroberts7577" <chrisroberts7577@gmail.com> wrote in message
news:3c3e10be-60ce-430e-a7e5-6d3f075d95f1@e39g2000hsf.googlegroups.com...
On Aug 12, 11:16 pm, Franc Zabkar <fzab...@iinternode.on.net> wrote:

On Tue, 12 Aug 2008 19:39:13 -0400, "Michael Kennedy"
m...@nospam.com> put finger to keyboard and composed:





"Chrisroberts7577" <chrisroberts7...@gmail.com> wrote in message
news:e0fe2364-0049-47f5-9912-f92b04b58e9d@2g2000hsn.googlegroups.com...
I need help getting help, finding a replacement board, or even finding
the schematic for an AOC (A42HD84) Plasma tv. I believe the main
power supply board (Samsung, LJ44-00092C) is the problem.

When I got the TV there was a blown fuse on the board. See some pics
of the board here:http://chrisroberts7577.googlepages.com/plasmarepair

When the board gets power there is only one voltage correctly present,
all others are non-existent.

Any help or guidance anyone can provide would be greatly appreciated.

The picture you posted doesn't look like a burnt out fuse. It loooks more
like an electrolytic capacitor that exploded. What does the board say in
the
area where you removed this component.

Mike

I thought the red component in this pic
...http://chrisroberts7577.googlepages.com/IMG_3011.jpg/IMG_3011-full;in...

... looked like one of these time delay
fuses:http://web.archive.org/web/20021016114001/http://www.cooperet.com/pdf...

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Frank is correct. Luckily I found the cap of the fuse in the TV. It
must have shot off when the fuse blew. So I was able to pull the p/n
off of it and get a replacement for it easily (Free thanks to free
samples).

-Chris

Ah... I was just looking at the first pic. I can see that you are correct.

Mike

 

[Arfa Daily]

"EADGBE" <hwbosshoss@comcast.net> wrote in message
news:f6b928ff-c3db-40ab-87fb-2f83bc25c24b@k13g2000hse.googlegroups.com...

Thanks, as usual, for all the great info so far.

I forgot to mention that I did try cleaning the laser lens. I used
91% isopropyl alcohol, which usually works pretty well, unless there
is a better method that I don't know about.

IPA is fine, although 'electronics grade' is usually a little purer than
that at 99.7%

Arfa

 

[William Sommerwerck]

"Yianni" <9jir_2006@yahoo.gr> wrote in message
news:1218677883.639830@athprx04...

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:mK2dnTk89dAwWT_VnZ2dnUVZ_jSdnZ2d@comcast.com...

The transducer is probably highly resonant at the operating frequency.
If you change the frequency, output is likely to be greatly reduced.

I don't think the transducer is so high resonant. At least the specific
one.
On the other hand, I would like to try. Do you know which parts to change?

I'm going to be nasty. What needs changing is your attitude.

Why are you wasting our time? You haven't supplied a manufacturer or a model
number, or a place to find a schematic. Why do you think anyone would have
the knowledge to suggest a specific change for an unknown product?

Furthermore, the answers I and others gave were "reasonable" in the context
of the question you asked and the overall design of such products.

If you know so much about the unit, modify it yourself.

 

[William Sommerwerck]

There's probably a pair of power transistors or MOSFETs that's
a power oscillator. If you trace around that area, it could help.
But no guarantees. But assuming it is resonant, that may be
part of what determines the frequency.

Particularly if it's an inexpensive product. It would make sense to have the
circuit oscillate at the natural frequency of the transducer.

 

[Arfa Daily]

"NVT" <nguyen-van-tung@wanadoo.fr> wrote in message
news:48a4682f$0$941$ba4acef3@news.orange.fr...

Hi,
I am looking for datasheet of IC STK 403-100
Thank you

I've sent a copy of a service manual for a JVC which uses it, direct to your
posting address. Hope this helps. If you have any problems receiving it,
mail me direct off-group

Arfa

 

[William Sommerwerck]

The transducer is not as these you referred to the other post. These
transducers are the "professional" transducers. This in the specific
ultrasonic cleaner is more like a buzzer than a conventional transducer.
It's diametre is twice than a conventional buzzer. Of course there is a
small possibility to resonate to a specific frequency, but I think not.

Your ignorance is wide and deep.

"Buzzers" are, indeed, resonant. In fact, most mechanical systems are
resonant. When you combine a mass with a restoring force, you get a
resonance.

 

[Arfa Daily]

<laseranddvdfan@aol.com> wrote in message
news:536c6a0b-431d-42e5-a82a-9a4a051579d5@p25g2000hsf.googlegroups.com...

I have an Onkyo TX-82 stereo receiver.

What happens is that, at random moments during use, the speaker
protection relay may open and cut the sound and then close.

I've tried reflowing all solder joints on the power amp board and
replaced various electrolytic capacitors, but to no avail. The
receiver keeps cutting out at random times.

The receiver seems to amplify normally, even up to the point where the
relay opens.

I'm guessing that the relay itself could be at fault, but how? I
physically tap the relay during use and it doesn't exhibit any faults.

Any suggestions on what could be going on?

Bad joints on the relay coil connections. Bad joints in the power supply
causing one rail to drop out momentarily. Bad joints in the relay control /
fault sense circuit. Resistor on relay delay timing going high / open.
Timing cap int o/c. Genuine problem such as defective speaker or wiring.
Those are the most common problems I come across.

Arfa

 

[DaveM]

<laseranddvdfan@aol.com> wrote in message
news:536c6a0b-431d-42e5-a82a-9a4a051579d5@p25g2000hsf.googlegroups.com...

I have an Onkyo TX-82 stereo receiver.

What happens is that, at random moments during use, the speaker
protection relay may open and cut the sound and then close.

I've tried reflowing all solder joints on the power amp board and
replaced various electrolytic capacitors, but to no avail. The
receiver keeps cutting out at random times.

The receiver seems to amplify normally, even up to the point where the
relay opens.

I'm guessing that the relay itself could be at fault, but how? I
physically tap the relay during use and it doesn't exhibit any faults.

Any suggestions on what could be going on?

You can probably look elsewhere for the fault. I would first suspect that the
circuitry that controls the relay, i.e., the protection circuitry, is
activating.

Some possible reasons that the protection circuitry is opening the relay...
(1) DC offset voltage is appearing at the speaker terminals. Causes... Idle
current set wrong or component failure in the amplifier chain causing the offset
to go haywire.
(2) Temperature compensation circuitry faulty. Causes... defective temperature
sensing component (thermistor, diode, transistor).
(3) Protection circuitry faulty. Causes... component failure in that area.
(4) Anything else that would upset the DC balance in the amplifier.

Things to look for:
Check for DC voltage present at the speaker terminals. If it's more than a few
millivolts, you need to find the reason for it.
Is the DC offset only on one channel (more likely) or both (unlikely)? Use the
good channel to compare voltage measurements along the amplifier chain and try
to isolate the bad stage.
Does the protection relay activate with no audio, or only with audio present?
Do you have a schematic of the unit?
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Experience: What you get when you don't get what you want

 

[Stacey Chuffo]

"ape shall not kill ape" <cerebureaucracy@hotmail.com> wrote in message
news:79db3f92-389d-4b50-9948-7b1df9325c7b@d45g2000hsc.googlegroups.com...

http://cgi.ebay.com/Daewoo-97P1RA3AA0-Remote-Control-DVD-Player-Recorder_W0QQitemZ230167357428QQcmdZViewItem?_trksid=p3286.m20.l1116#ebayphotohosting

Will the above mentioned remote control work for Daewoo 5800 Dvd
Player?

How the fuck are we supposed to know?

 

[Stacey Chuffo]

"Samuel M. Goldwasser" <sam@seas.upenn.edu> wrote in message
news:vdy078hd.fsf@seas.upenn.edu...

I may need a single 22V10-10 or -15 programmed. I thought my PAL
programmer
was working but the burnt PAL behaves strangely in a way that suggests
it may have internal incorrect logic. It also doesn't pass the
programmer's
test wiht respect to the test vectors (but I'm not sure that this ever
really worked properly).

I'll pay for the PAL or send a raw one and the .JED file to anyone who
might volunteer.

Or, if someone has a working programmer they'd like to sell.....

Thanks!

Go to JDR microdevices. They sell that kind of shit.
http://www.jdr.com/ or 1-800-538-5000

--
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.

 

[William Sommerwerck]

Checking for DC in the speaker terminals. Bank A left reads 8.3mV.
Bank A right reads 5.9mV. Bank B left reads 8.4mV. Bank B right reads
6.1mV.

Have you sat there watching the meter to see if the offset jumps up when the
relay opens? (I'm sure you have better things to do with your time!) Some
DMMs have a trending feature that keeps track of the highest voltage.

Arfa's suggestions are a good place to start.

 

[N Cook]

<laseranddvdfan@aol.com> wrote in message
news:420d6f6a-bd8e-4646-9939-e59ea2e243a6@j22g2000hsf.googlegroups.com...
On Aug 16, 8:34 pm, "DaveM" <masondg4...@comcast99.net> wrote:

laseranddvd...@aol.com> wrote in message

news:536c6a0b-431d-42e5-a82a-9a4a051579d5@p25g2000hsf.googlegroups.com...



I have an Onkyo TX-82 stereo receiver.

What happens is that, at random moments during use, the speaker
protection relay may open and cut the sound and then close.

I've tried reflowing all solder joints on the power amp board and
replaced various electrolytic capacitors, but to no avail. The
receiver keeps cutting out at random times.

The receiver seems to amplify normally, even up to the point where the
relay opens.

I'm guessing that the relay itself could be at fault, but how? I
physically tap the relay during use and it doesn't exhibit any faults.

Any suggestions on what could be going on?

You can probably look elsewhere for the fault. I would first suspect that
the
circuitry that controls the relay, i.e., the protection circuitry, is
activating.

Some possible reasons that the protection circuitry is opening the
relay...
(1) DC offset voltage is appearing at the speaker terminals. Causes...
Idle
current set wrong or component failure in the amplifier chain causing the
offset
to go haywire.
(2) Temperature compensation circuitry faulty. Causes... defective
temperature
sensing component (thermistor, diode, transistor).
(3) Protection circuitry faulty. Causes... component failure in that area.
(4) Anything else that would upset the DC balance in the amplifier.

Things to look for:
Check for DC voltage present at the speaker terminals. If it's more than a
few
millivolts, you need to find the reason for it.
Is the DC offset only on one channel (more likely) or both (unlikely)? Use
the
good channel to compare voltage measurements along the amplifier chain and
try
to isolate the bad stage.
Does the protection relay activate with no audio, or only with audio
present?
Do you have a schematic of the unit?
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters
in the
address)

Experience: What you get when you don't get what you want

The relay trips whether or not there is any audio and whether or not
the power amp circuit has any load or not.

Checking for DC in the speaker terminals. Bank A left reads 8.3mV.
Bank A right reads 5.9mV. Bank B left reads 8.4mV. Bank B right reads
6.1mV.

&&&&&

all quite normal

Monitor the main +/- DC rails for changes/imbalance. Monitor the voltage
over any zener diodes associated with the protection circuitry.


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

 

[Arfa Daily]

<laseranddvdfan@aol.com> wrote in message
news:1e0e4198-8130-4217-9be7-7de13d2e0c6e@79g2000hsk.googlegroups.com...
On Aug 16, 9:20 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

Checking for DC in the speaker terminals. Bank A left reads 8.3mV.
Bank A right reads 5.9mV. Bank B left reads 8.4mV. Bank B right reads
6.1mV.

Have you sat there watching the meter to see if the offset jumps up when
the
relay opens? (I'm sure you have better things to do with your time!) Some
DMMs have a trending feature that keeps track of the highest voltage.

Arfa's suggestions are a good place to start.

Right now, I want to figure out what is going on and I have the time
at this moment to do that.

I measured the power and, on the left channel, the offset fluctuates
between a peak of 11.3 mV and 8.3 mV. Is this significant?

Unfortunately, I missed the meter reading right at the moment the
protection relay tripped.



It's hard to say whether or not that is significant. In itself, in terms of
absolute voltage, it is not significant. Imbalances up to about 20mV are not
uncommon, and are nothing for concern. However, the fact that it is
fluctuating may indicate that some component is 'hovering' around its
breaking down point, or that one of the rails is not stable. It is not
really usual for the voltage, whatever its actual value, to fluctuate. Does
your DMM have a peak hold facility as suggested elsewhere? This will tell
you if the midpoint shifts substantially at the time of failure. However,
note that if the relay circuit is 'quick', it might be *too* quick for the
DMM to see the voltage increase, before the relay disconnects it, so really,
you need to be taking any measurements actually at the amplifier output,
prior to the relay.

Does this amp have a set of discrete component output stages, or are they
STK hybrids ?

Monitor the supply rails as well - particularly those to the output stages -
and see if they are moving by a similar amount as the output offset. In DC
coupled amps, a very tiny shift in conditions back in a preamp stage, can
upset the DC conditions so much in the output stages, as to cause a relay
trip-out, which can make them very frustrating to troubleshoot. Use the butt
end of a reasonable sized screwdriver to have a bit of a bash around, to see
if you can provoke the problem at will. If you can, then swap to a biro pen
to pin down the actual area, and possibly, component.

You can also try a hairdryer, and a can of freezer, both sides of the board.
Bad joints which don't readily show up with disturbance testing, are often
surprisingly sensitive to heat and cold. Does the problem seem to get worse
or better the longer the amp is on ? Is it worse when the amp is 'doing some
work' ? All possibly significant factors in arriving at a diagnosis.

Arfa

 

[Arfa Daily]

<laseranddvdfan@aol.com> wrote in message
news:7956f71e-9fee-41a7-b61a-86a80a6722f9@m3g2000hsc.googlegroups.com...

If I may ask first.

Would too high a voltage for the idling current on one of the channels
be a possible cause?

There must be a good reason why the idle current is four times what it
should be. You have suggested elsewhere, that adjusting the pot has
corrected the situation, and appears to have stopped the fault from
occuring. In itself, the idle current being that high, is unlikely to cause
the protect circuit to drop the relay out intermittently. Usually, the only
effect will be that the output transistors on the affected channel, will run
rather hotter than would be considered 'comfortable'. That said, if you had
a 'dicky' pot, it may well be going intermittently effectively o/c, as the
wiper makes and then doesn't. The effect of this could be to shoot the idle
current up way high, which might be enough to trip the protect circuit,
depending on exactly what parameters of the output stages, it is monitoring.

If you have been able to correct the bad idle current to the specified
value, the next thing that you should do is to compare the pot's set
position, or its resistance setting, to the pot on the good channel. If it
is near enough the same, then the most reasonable conclusion is that you did
have a dicky pot, and rotating it has cleared the condition. A further
confirmation of this, would be if the pot had been returned virtually to its
original set point, and the idle current value was now correct. However, if
the pot has had to be rotated a significant distance from where it was
originally set, and is now set at a completely different point / resistance
to the pot on the other channel, then you have a genuine fault, which needs
locating and correcting.

If a preset pot goes intermittent, usually a drop of switch cleaner /
lubricant on the track, and a good scrub from end to end a few times (with
the amp turned off, of course ... ) is enough to produce a long term cure.

Arfa

 

[Arfa Daily]

"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message
news:ialha459fbe4dm40e780iq267kd3ov0soa@4ax.com...

On Mon, 18 Aug 2008 00:56:26 +0100, "Arfa Daily"
arfa.daily@ntlworld.com> put finger to keyboard and composed:

laseranddvdfan@aol.com> wrote in message
news:7956f71e-9fee-41a7-b61a-86a80a6722f9@m3g2000hsc.googlegroups.com...
If I may ask first.

Would too high a voltage for the idling current on one of the channels
be a possible cause?

If you have been able to correct the bad idle current to the specified
value, the next thing that you should do is to compare the pot's set
position, or its resistance setting, to the pot on the good channel. If it
is near enough the same, then the most reasonable conclusion is that you
did
have a dicky pot, and rotating it has cleared the condition.

It stands to reason that rotating the pot fully CCW or CW should not
damage the amp, otherwise not many would have left the factory. If the
trimmer is wired as below, then why not measure the idling
voltage/current at both extremities and verify whether this trips the
relay?

|---|
| |
| V
--|-/\/\/\/\/\---

If neither setting causes the relay to trip, then the problem must lie
elsewhere.

- Franc Zabkar
--

Not disputing the "should" Franc, I was just thinking that if the pot was a
bit touchy, then whacking it from one end to the other with it farting
about, might just result in the magic smoke being released from the outputs.
Just being careful, which you, more than most on here, should appreciate is
a sensible thing to do with a DC coupled amp ... d;~}

Arfa

 

[Arfa Daily]

"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message
news:gu5ia49k5eanhubb6spbirvjemrvpi5bei@4ax.com...

On Mon, 18 Aug 2008 15:44:29 +1000, Franc Zabkar
fzabkar@iinternode.on.net> put finger to keyboard and composed:

Here it is:
http://www.eserviceinfo.com/download.php?fileid=37140

Page 25 appears to be the relevant section.

It appears that the protection circuitry is in two parts. Q551 and
Q651 sense the current in the emitter resistors, whereas Q552 and Q553
sense the DC offset at the amplifier outputs. Both protection circuits
trigger the Protect signal at pin 24 of the LM6405G microprocessor via
Q554, and the uP then trips the relay via pin 30.

Disconnecting R556 will disable the DC offset protection, and
disconnecting R553 and R653 will disable the current overload
protection on the left and right channels, respectively. Disconnecting
each of the three resistors one at a time may help narrow down the
source of the problem.

By my reckoning, you would need a DC offset of 2.7V before Q552 would
turn on, and you would need 1.2A in the emitter circuit of Q552 and
Q553 in order for Q551 to turn on. The latter is much higher than your
out-of-spec 60mA idling current.

- Franc Zabkar
--

OK then, how about this for a scenario. As both pots are now set in about
the same place to get the same idle current, and one of them wasn't before,
it follows that the one which was wrong, had almost certainly been set
wrongly for a long time. This means that the transistors and heatsink on
that channel have been running much hotter than they should have. If it uses
mica washers with heatsink paste, rather than silicone rubber insulators,
the excess heat may have dried the paste out over the years, such that it is
now doing a poor job, and the transistors can get hot enough to start
running away, which creates a large emitter current, which is then sensed,
and causes the shutdown. Even if the insulators are rubber, a close
inspection might reveal that the excess heat has done them no good, and they
have gone hard. Just a thought, as I agree with your thoughts regarding
offdet and current trip points.

Arfa

 

[Mark D. Zacharias]

<biddy67@gmail.com> wrote in message
news:b61351a4-6857-4133-9c2b-84e1f9d93a14@79g2000hsk.googlegroups.com...

I have the KF-60WE610. Bought in Dec 2003. Replaced the first lamp
burn out on Aug 2007. Has burned out again in only 1 year, probably
about 1,000 hours. Replacement lamp does not have either OSRAM or
Philips markings, but is Made in Japan. Lamp was replaced by circuit
city under warranty.

Given that the tv set is 5 years old and a lamp has burned out so
quickly, would it make sense to go ahead and replace the lamp ballast
(driver) as a preventive measure? I'm guessing these are subjected to
a harsh operating environment, degraded, and may have played a part in
the early lamp failure. Do lamp failures decline after ballast
replacement? The part is only $106 at the Sony site. The part
appears to have an upgraded part number, so it is possible that there
have been improvements in its design.

The lamp driver pretty much either works or it doesn't. Examine it to see
that it's plug-in connections aren't charred, and do make sure the fans are
clean. They often get so occluded with dust that the lamp gets insufficient
cooling, shortening lamp life.


Mark Z.

 

[William Sommerwerck]

I don't know why but, after setting the idling current to factory
specs, the amp appears to be stable; the heatsink and transistors
don't run hot and the protection never trips while playing music
through it for 4 hours straight with a pair of Yamaha S55 monitors.
It never worked that well until after the adjustment was done.

There are two ways to go about servicing...

1. Find out exactly what's wrong.

2. Get the device working again.

Most people smart enough to service electronic equipment tend to lean toward
the former. But it's inefficient, and should be reserved for times when it
seems to be really needed.

In your case, it appears that #2 worked (for whatever reason). I would
suppress my curiosity -- your "I don't know why, but..." -- for the time
being and simply enjoy the amplifier.

 

[Dave Plowman (News)]

In article
<a7720beb-e1f9-4481-bd1f-58571ab7f285@i76g2000hsf.googlegroups.com>,
<biddy67@gmail.com> wrote:

What is meant by this statement as it relates to television repair?

Means a clip has probably broken off.

--
*What happens when none of your bees wax? *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[GregS]

In article <a7720beb-e1f9-4481-bd1f-58571ab7f285@i76g2000hsf.googlegroups.com>, biddy67@gmail.com wrote:

What is meant by this statement as it relates to television repair?

MAke it look pretty and neat and sometimes means to route the HV
away from other components, and , or to reinsulate.



greg