Toshiba TV29C90 problem; Image fades to black...

[Chrisroberts7577]

On Aug 12, 4:36 pm, Franc Zabkar <fzab...@iinternode.on.net> wrote:

On Tue, 12 Aug 2008 11:37:37 -0700 (PDT), Chrisroberts7577
chrisroberts7...@gmail.com> put finger to keyboard and composed:

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.

At the risk of stating the obvious, the fact that you are getting only
one voltage (the standby voltage?) suggests that your set is not
coming out of standby.

One thing that strikes me straight away is that the solder joints
around various coils (L465 & L466 & L341 ?) are not shiny. I usually
reflow the solder at all the coils, whether good or bad.

http://chrisroberts7577.googlepages.com/IMG_3017.jpg/IMG_3017-full;in...

The most obvious approach is to trace out the circuit around the blown
fuse, or at least test all the active components in that area. Likely
culprits would be the two MOSFETs on the adjacent heatsink which would
probably be driven by the IR2109 Half-Bridge Driver IC:

http://www.irf.com/product-info/datasheets/data/ir2109.pdf

Another candidate could be an open NTC resistor near the fuse. These
resistors are used to limit the inrush current to the main bulk
capacitor(s).

There must also be a signal (PS_ON ?) coming in via this board ...

http://chrisroberts7577.googlepages.com/IMG_3022.jpg/IMG_3022-full;in...

... that switches on the main PSU. Confirm that this signal is
changing state when you turn the set on, and then check to see that
the output of this board is switching the AC supply.

BTW, AOC is a well known monitor manufacturer.

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

Frank thanks for your help. Here are some answers to your questions.

The TV is going from standby to the ON state fine. I've checked that
small board and it seems to be doing it's job correctly. The LED on
the TV changes colors when I press the on button, you hear a relay
switch, and that's when the single voltage on the main board appears.
The TV will not switch back into the standby state however.

I will try reflowing those solder joints tomorrow if I can remember to
bring the board in to work. I was really disappointed in the quality
of the board when I took a look at it. There is still flux all over
it, like it never got cleaned.

I should be able to check the mosfet and resistor tonight. Hopefully
I can find something.

Thanks for your input.

 

[Chrisroberts7577]

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

 

[PeterD]

On Wed, 13 Aug 2008 08:48:56 -0400, Blattus Slafaly
<boobooililililil@roadrunner.com> wrote:

PeterD wrote:
On Tue, 12 Aug 2008 13:10:58 -0400, Blattus Slafaly
boobooililililil@roadrunner.com> wrote:

What's that green shit in the URL on secure sites? I never saw an
explanation of it.

ink... Same stuff they print magazines from.

I see you don't know either.

Sure I know... Whether I'd reply with the correct answer is another
matter. The topic, discussed in the proper group will quickly tell you
all about HTTPS and certificats. But you are not interested in that,
only in generating a troll, right?
Peter's Troll-o-Meter

Not Troll Troll
0 1 2 3 4 5 6 7 8 9 10
/
/
/
/
/
/
/
O

(Pegged the needle!)

 

[PeterD]

On Wed, 13 Aug 2008 08:49:44 -0400, Blattus Slafaly
<boobooililililil@roadrunner.com> wrote:

Spamm Trappe wrote:
On Tue, 12 Aug 2008 13:10:58 -0400, Blattus Slafaly wrote:
What's that green shit in the URL on secure sites?
I never saw an explanation of it.

So... you were putzing around with your browser and saw some "green
shit" (did you sniff it?) and then fired up your usenet client and
decided that going to *sci.electronics.repair* was the best and most
appropriate place to ask about it?

I know --- rhetorical question.

'I don't know' is much shorter more direct answer.

Idiot is even shorter.

 

[Blattus Slafaly]

PeterD wrote:

On Wed, 13 Aug 2008 08:48:56 -0400, Blattus Slafaly
boobooililililil@roadrunner.com> wrote:

PeterD wrote:
On Tue, 12 Aug 2008 13:10:58 -0400, Blattus Slafaly
boobooililililil@roadrunner.com> wrote:

What's that green shit in the URL on secure sites? I never saw an
explanation of it.
ink... Same stuff they print magazines from.
I see you don't know either.

Sure I know... Whether I'd reply with the correct answer is another
matter. The topic, discussed in the proper group will quickly tell you
all about HTTPS and certificats. But you are not interested in that,
only in generating a troll, right?
Peter's Troll-o-Meter

Not Troll Troll
0 1 2 3 4 5 6 7 8 9 10
/
/
/
/
/
/
/
O

(Pegged the needle!)

You sure it's not your cock meter.

--
Blattus Slafaly ? 3 7/8

 

[PeterD]

On Wed, 13 Aug 2008 18:42:04 -0400, Blattus Slafaly
<boobooililililil@roadrunner.com> wrote:

PeterD wrote:
On Wed, 13 Aug 2008 08:48:56 -0400, Blattus Slafaly
boobooililililil@roadrunner.com> wrote:

PeterD wrote:
On Tue, 12 Aug 2008 13:10:58 -0400, Blattus Slafaly
boobooililililil@roadrunner.com> wrote:

What's that green shit in the URL on secure sites? I never saw an
explanation of it.
ink... Same stuff they print magazines from.
I see you don't know either.

Sure I know... Whether I'd reply with the correct answer is another
matter. The topic, discussed in the proper group will quickly tell you
all about HTTPS and certificats. But you are not interested in that,
only in generating a troll, right?
Peter's Troll-o-Meter

Not Troll Troll
0 1 2 3 4 5 6 7 8 9 10
/
/
/
/
/
/
/
O

(Pegged the needle!)

You sure it's not your cock meter.

Clearly it doesn't show your intelligence, does it?

 

[JeffM]

RF King wrote:

AAA RF Products
[SPAM]
San Clemente, CA

 

[Franc Zabkar]

On Fri, 15 Aug 2008 12:30:37 -0700 (PDT), jrshedden
<jrshedden@gmail.com> put finger to keyboard and composed:

Hi All,

I still enjoy this forum, even though I have to sift through the spam.
It's a real shame.

I have a Supermicro computer with a 'triple redundant' power supply.
That means 3x250 watt modules in a backplane and rated at 500 watts.
You can loose one module and still be in spec.

I lost a module, had it repaired under warrantee, and lost the the
same module again. It is an Ablecom Model SP 252-TC and I can find
nothing on it, including the card edge connector pinout. It looks very
well made and it I see quality components crammed inside. Supermicro P/
N is PWS-0035(M). Some research indicates it may have been made by
LiteOn.

The module will run for 30 seconds, then shut down for 20, then
repeat. An 'amp clamp' on the input shows about an amp when it's up,
and less than 100 mA when it's down, so I have to figure out why it
decides to give up and retry.

I could really use the edge card pinout of this type of supply and any
hints as to this type of symptom to save me reverse engineering time.
I'm thinking thermal, and if I can coax the supply into operation on
my bench, freeze spray will probably indicate the problem in short
order.

I am aware of proper safety procedures.

Thanks in advance!

Jim S.

All I could find were the ratings of the outputs:
http://www.supermicro.com/support/resources/pws/

The obvious thing to check when you suspect thermal problems is the
fan.

Otherwise, with the unit powered down, can you probe for continuity
between the backplane pins and known voltages on the motherboard (eg
PCI slot) and peripherals?

http://pinouts.ru/Slots/PCI_pinout.shtml
http://pinouts.ru/Slots/IndustrialPCI_pinout.shtml

I've never worked with a redundant, hot swappable PSU, so I don't know
if what I'm asking makes any sense.

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

 

[Jerry G.]

Normaly, the code sets will match to some degree. For newer or changed
options there may be different codes, and therefore these functions
will not work.

Sometimes I have seen in the same manufacture and different
manufactures to have the codes crossed between their different models.
A button on the remote that would change the channels on one model
would be calling up a menu on another model.

The other thing to look at is that sometimes the manufactures will
contract to different assemblers to make their products. These
different assemblers may use their own complete code set, and
therefore thei codes will not be compable.

In the end, you will not really know until you try the remote and see
for yourself.


Jerry G.

__


On Aug 15, 8:22 pm, ape shall not kill ape
<cerebureaucr...@hotmail.com> wrote:

http://cgi.ebay.com/Daewoo-97P1RA3AA0-Remote-Control-DVD-Player-Recor...

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

 

[Jerry G.]

I have not worked on that particular supply. I found that on most of
the supplies that I have serviced, they had caps that failed or became
thermo sensitive.

What I can suggest to get an ESR meter and test all the caps. Heat the
module up with a heat gun so that it is warm when testing the caps.
All the caps that read too high in ESR should be changed.

If the fault is more complicated, the supply will be very difficult to
service without the schematics and a source for the proprietary parts.
In the modern supplies they use a lot of SMD technology with very
specialized IC's, custom made transformers and inductors and devices.

As for myself, I found that the majority of times these supplies are
not worth to service. You can end up spending many hours and a lot of
money on parts. In the end you may have a supply that you cannot have
some specialized parts you need and you spent a lot trying to fix it.


Jerry G.


__


On Aug 15, 3:30 pm, jrshedden <jrshed...@gmail.com> wrote:

Hi All,

I still enjoy this forum, even though I have to sift through the spam.
It's a real shame.

I have a Supermicro computer with a 'triple redundant' power supply.
That means 3x250 watt modules in a backplane and rated at 500 watts.
You can loose one module and still be in spec.

I lost a module, had it repaired under warrantee, and lost the the
same module again. It is an Ablecom Model SP 252-TC and I can find
nothing on it, including the card edge connector pinout. It looks very
well made and it I see quality components crammed inside. Supermicro P/
N is PWS-0035(M). Some research indicates it may have been made by
LiteOn.

The module will run for 30 seconds, then shut down for 20, then
repeat. An 'amp clamp' on the input shows about an amp when it's up,
and less than 100 mA when it's down, so I have to figure out why it
decides to give up and retry.

I could really use the edge card pinout of this type of supply and any
hints as to this type of symptom to save me reverse engineering time.
I'm thinking thermal, and if I can coax the supply into operation on
my bench, freeze spray will probably indicate the problem in short
order.

I am aware of proper safety procedures.

Thanks in advance!

Jim S.

 

[Franc Zabkar]

On Sun, 17 Aug 2008 20:58:49 -0700 (PDT), laseranddvdfan@aol.com put
finger to keyboard and composed:

Would it be okay for me to e-mail you a PDF of the service manual?

Yes. I'll upload it to eserviceinfo for the group, if that's OK,
otherwise I'll put it on my web site.

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

 

The manual has been uploaded to you.

However, it has been sent using a different e-mail address than
"laseranddvdfan@aol.com."

 

[Franc Zabkar]

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

 

Forgot to follow the directions on your sig regarding sending a
message to your e-mail.

The PDF has been re-sent.

 

[Franc Zabkar]

On Mon, 18 Aug 2008 16:34:42 +1000, Franc Zabkar
<fzabkar@iinternode.on.net> put finger to keyboard and composed:

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.

Sorry, that should be Q508 and Q507, not Q552 and Q553.

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

 

On Aug 18, 2:34 am, Franc Zabkar <fzab...@iinternode.on.net> wrote:

On Mon, 18 Aug 2008 15:44:29 +1000, Franc Zabkar
fzab...@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
--
Please remove one 'i' from my address when replying by email.

I guess the offset is fixed instead of adjustable. And, I'm guessing
that I'm most likely wrong but, does the idling current adjustment
have any relation to and significant effect with the DC offset?

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.

And, when setting R607 to where the test lead shows 7.5mV on R ch. and
doing the same for R507 for L ch., the resistance reading were, more
or less, ended up being the same on both pots.

But, when I set R607 to a setting that ends up reading 100mV at the
test point, the heatsink gets kind of toasty and the protection kicks
in within a few minutes.

 

[jrshedden]

Hi,

Thanks for the 2 replies. I hope I'm properly posting so you both can
see this. Am I correct that a 'Reply' is to all and a 'Reply to
Author' is in response to a particular post?

Franc:

Thanks for the pinouts. There are 3 backpanes in the server. Once is
the motherboard I/O expansion (PCI-X and PCIe on this one). The second
is the SCSI backplane where up to 7 disk drives plug in. The third is
the power supply backplance (Supermicro calls it the 'power
distributor') where 3 identical 250 watt power supplies slide in from
the back of the machine and connect via edge card connectors. Each
power supply has its own power input and its own fan, so the server
has 3 power cords. When the supply goes down, its fan stops because it
probably runs off it's own 12 volts, but it is going strong when the
supply is up and the exhaust temperature matches the other 2 within 3
or 4 degrees F.

Jerry:

I built the Dick Smith ESR tester, and I will check all the caps when
heated. I'm taking your advice and replacing the supply, but I will
probably hack around the module to see if I get lucky. It will take
some luck or an inordinate amount of time without schematics.


Solution:

ACS Industrial services would fix the module ($250 minimum) and
Supermicro would sell me a refurbished 760 watt triple redundant (3
modules + backplane or power distributor) for $300 or $330 (I forget).
It's ordered and on the way. Too bad the &60 watt modules are not
compatible with the old backplane.

If I figure out the module problem I will repost the result.

Thanks for the help.

Jim

 

On Aug 18, 4:59 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"Franc Zabkar" <fzab...@iinternode.on.net> wrote in message

news:gu5ia49k5eanhubb6spbirvjemrvpi5bei@4ax.com...



On Mon, 18 Aug 2008 15:44:29 +1000, Franc Zabkar
fzab...@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

The transistors do, indeed, use mica insulators with heatsink paste.

Having replaced capacitors and redoing solder on the board, I took it
upon myself to clean out the old thermal paste off the transistors,
mica, and heatsink and used fresh paste.

 

On Aug 18, 7:29 am, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

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.

I also tend to lean on the latter.

As the saying goes, if it works then it's not broken. If it's not
broken, don't fix it.

 

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.
Arfa

As for how R607 had been set wrong before, I have a very wild guess
about that.

I bought the amp used as a present to a friend, but in the midst of
testing, I found that the receiver had problems with intermittent
power loss. Turned out to have been cold joints on the secondary
power supply block. I think what could've happened was that whoever
owned the thing before I bought it might have tried to "fix" it by
tweaking the potentiometer. What doesn't support this, however, was
that it seems only R607 had been altered. The other pots, such as
R507 and the pots on the preamp circuit do not appear to be a altered
as the tuner and other parts of the preamp section appear to work
properly. Usually, a really bad weekend tech may just tweak anything
indiscriminately until he thinks he fixed it.

I think it makes more sense that R607 has drifted in value somehow.