Hitachi 37LD9000 Inverter tripping, Story in pictures

[jango2]

Hitachi 37LD9000 Inverter tripping, green led on, sound ok, no
picture.
Pics contain textual narration.

http://i596.photobucket.com/albums/tt46/jango_2/Image1.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image2.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image3.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image4.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image5.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image6.jpg
Jango

 

[PeterD]

On Wed, 25 Nov 2009 22:10:44 -0800 (PST), jango2
<crow_slapper@yahoo.co.uk> wrote:

Hitachi 37LD9000 Inverter tripping, green led on, sound ok, no
picture.
Pics contain textual narration.

http://i596.photobucket.com/albums/tt46/jango_2/Image1.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image2.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image3.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image4.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image5.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image6.jpg
Jango

I would not leave that stryofoam in there, it could present a fire
hazard.

 

[Allahbux]

On Nov 25, 10:10 pm, jango2 <crow_slap...@yahoo.co.uk> wrote:

Hitachi 37LD9000 Inverter tripping, green led on, sound ok, no
picture.
Pics contain textual narration.

http://i596.photobucket.com/albums/tt46/jango_2/Image1.jpghttp://i596.photobucket.com/albums/tt46/jango_2/Image2.jpghttp://i596.photobucket.com/albums/tt46/jango_2/Image3.jpghttp://i596.photobucket.com/albums/tt46/jango_2/Image4.jpghttp://i596.photobucket.com/albums/tt46/jango_2/Image5.jpghttp://i596.photobucket.com/albums/tt46/jango_2/Image6.jpg
 Jango

 

[jango2]

I would not leave that stryofoam in there, it could present a fire
hazard.

Wasn't planning to, just a temp fix till i get appropriate feedback
and find a solution, Thanks anyway Mr. Darby

 

On Thu, 26 Nov 2009 07:25:07 -0800 (PST), jango2
<crow_slapper@yahoo.co.uk> wrote:

I would not leave that stryofoam in there, it could present a fire
hazard.


Wasn't planning to, just a temp fix till i get appropriate feedback
and find a solution, Thanks anyway Mr. Darby
I can see three approaches.

The first is a brute force approach. It depends on sufficient space
between the perforated shield and the back of the TV. Judging by the
styrofoam experiment, a rectangular 'can' of that depth could be
constructed and the back shield modified so there is additional
clearance between the transformers and the (extended) shield.

The second is more elegant and more work to achieve. Inverter
controller ICs monitor a number of parameters, including output
voltage, CCFL current, and even drive current. Determine which
parameter is causing the shutdown. Then analyse the circuit to
determine if the setting is overly conservative, components have
drifted, or a component (driver?) is marginal for this application.
The solution might be as simple as changing one resistor, or as
complex as redesigning the driver circuitry.

The third is simple - check with Hitachi and determine if there is any
modification kit to resolve this problem. I don't hold a lot of hope
that there is, but ...

PlainBill

 

[jango2]

Thanks for respnding Bill

Brute force
hammer n punch?
i have clearance between back cover n shield
5 mm displacement? Wht if I cut another hole through?
smd filter caps on board too?
no schematics for inverter available, no marking on caps

How does the black patch and foil work anyways
How do i word this innocently to Hitachi to get them to hep?

 

On Fri, 27 Nov 2009 07:40:20 -0800 (PST), jango2
<crow_slapper@yahoo.co.uk> wrote:

Thanks for respnding Bill

Brute force
hammer n punch?
Well, I was thinking of something like a sheet metal nibbler (drill

hole in sheet metal, tip of nibbler goes through, nibble out opening
of any desired size ande shape). In this case, 'brute force' meant a
solution which avoided the sensitivity to metal without actually
repairing the design defect.

i have clearance between back cover n shield
5 mm displacement? Wht if I cut another hole through?
smd filter caps on board too?
There is a hole in the inner shield, I'm guessing it's about 5 cm x 7

cm. I would cut a rectangular hole 6 cm x 8 cm in the perforated
shield. Next, build a shallow rectangular pan 6 cm x 8 cm by 5 mm
deep with a 5 mm outer rim. Finally, attach the pan over the opening
you cut.

no schematics for inverter available, no marking on caps

How does the black patch and foil work anyways

I don't have a clue.

How do i word this innocently to Hitachi to get them to hep?
Why be innocent? I would start out assertive - "What is the reference

number for the service note, change order, or repair kit to solve the
inverter shut down problem on a 37LD9000 TV?"

PlainBill

 

[Franc Zabkar]

On Wed, 25 Nov 2009 22:10:44 -0800 (PST), jango2
<crow_slapper@yahoo.co.uk> put finger to keyboard and composed:

Hitachi 37LD9000 Inverter tripping, green led on, sound ok, no
picture.
Pics contain textual narration.

http://i596.photobucket.com/albums/tt46/jango_2/Image1.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image2.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image3.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image4.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image5.jpg
http://i596.photobucket.com/albums/tt46/jango_2/Image6.jpg
Jango

The datasheet for the Rohm BD9890FV inverter controller states that "a
strong electromagnetic field may cause the IC to malfunction":

http://www.rohm.com/products/databook/video/pdf/bd9890fv-e.pdf

However, the above warning may be a general one, as it occurs
alongside other general warnings including "mounting failures, such as
misdirection or miscounts, may harm the device".

What if you tried shielding the BD9890FV IC inside a metal box ???

Or what about a grounded metal plate above it, and a plate below it on
the underside of the PCB?

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