Musical surprise

[TerraHertz]

So, another day, another street-tossed large screen TV to disassemble. I like these very thin LCD side-backlit screens, and pick them up when I see them on the kerb. I have three or four (of their guts) now, with a project in mind to make a thin 'light table' using the side-illumination optics and LED drive electronics these provide.

The sticking point, is making a simple controller from an Arduino, to provide power on-off and LED lighting level control to the power supply board. Via whatever serial coms the TV uses between the main video board and the power board.

This is one I picked up on Monday. The usual - fractured LCD glass making interesting but useless patterns when turned on. Meaning the backlighting is working fine so go straight to disassembly.
Then turn it on again as bare boards on the bench, to see if the power board has a 'default LEDs on' mode if the main board is disconnected.

This one doesn't, but then... big surprise. After at least a minute it figures out it has been left on without a video source. Suddenly it starts playing music! A lengthy ambient piece, quite pleasant. Also the backlight LEDs fade up and down in brightness, matching the music.

What's good about that, is it means the LED brightness control serial line will be exercising continuously. All the better to protocol grab.

Speaking of which, it's about time I bought a modern small, relatively cheap lunchbox scope. One with various serial protocol capture and decode features built in. What models do people recommend? (He asks, hoping to avoid days and days of hunting and reading specs.)

[Zero999]

I wonder if the audio amplifier is any use for a project? The speakers, tend to be pretty crappy, so no good in anything requiring decent sound quality, but fine for basic sound effects.

Regarding the oscilloscope, if it needs to be portable, go for the Owon SDS7102, with a battery. It isn't as good as the Rigol DS1054, which is a little more expensive, but I find the portability more of an advantage.

[TerraHertz]

I wonder if the audio amplifier is any use for a project? The speakers, tend to be pretty crappy, so no good in anything requiring decent sound quality, but fine for basic sound effects.

If you needed a speaker driver amp with only digital audio input, perhaps. Looks like that area of the PCB could be cut free and used by itself. The IC:
  TI TAS5707
  20-W STEREO DIGITAL AUDIO POWER AMPLIFIER WITH EQ AND DRC
  https://www.ti.com/lit/ds/slos556b/slos556b.pdf

Regarding the oscilloscope, if it needs to be portable, go for the Owon SDS7102, with a battery. It isn't as good as the Rigol DS1054, which is a little more expensive, but I find the portability more of an advantage.

Actually for something like a scope, I'd avoid batteries. Just one more thing to go bad.  Don't need portability, it will always be used on a bench or close to power.
So far I can't see a list of serial protocols for the Rigol DS1054. I haven't paid much attention to new Rigol/Hantek scopes (or HP/Tek for that matter), but I do recall reading something about a model that could capture and decode many different serial bus protocols.  Sometime in recent years. That's a major attraction for me.

Btw the TV was a TCL   model 50P6US.   Having a quick skim of the user manual  (dl'd) just reminds me of why I avoid owning a TV these days.

[tunk]

No expert, but for an inexpensive DSO, you could look at the Hantek
2000 series which comes with RS232/UART, I2C, SPI, CAN, LIN decoding.
http://www.hantek.com/products/detail/17182

[tautech]

THz, will a 2ch DSO be adequate ?
Have a look at the 200 MHz SDS1202X-E.....SPI, I2C UART, CAN and LIN decodes as standard....and BTW don't let anyone tell you you can't decode SPI with a 2ch DSO as Clk Timeout settings allow expressly this.

[TerraHertz]

THz, will a 2ch DSO be adequate ?

Yes, quite. I already have lots of scopes, but they are all old and big. And I generally take the position 'if I can't get a service manual with schematics, then I'm not buying it.' Hence my not having any modern test gear.

But I currently have some spare cash, so I'm making a list of nice things to buy. A modern small scope with 'virtual phosphor' style display is at the top. (I hate jaggy displays.)
'Decoders' is a requirement because it's cool, and saves mucking around with big logical analyzers.
And because I _thought_ I have a current need - getting a TV LCD backlight power board under control.

Have a look at the 200 MHz SDS1202X-E.....SPI, I2C UART, CAN and LIN decodes as standard....and BTW don't let anyone tell you you can't decode SPI with a 2ch DSO as Clk Timeout settings allow expressly this.

Ha ha, no one has, and I wouldn't have known. Never used SPI... so far.
But anyway...
Thanks for the suggestion. It and the Rigol DS1054 are under consideration.  I need to read the 'scopes matrix' thread.
I'll still buy such a scope soon but am no longer in a rush, because I hit the jackpot with this 'plays music' scrapped TV. The LED supply controller IC turns out to use an analog brightness control signal!

LED backlight switchmode supply chip, is a 16 pin SMD. Markings:
  OZ9976AGN    <--- This is the part number
  CJ6L26.1N
  1747A1

Pretty much the only search result was this nightmare site:
http://html.datasheetbank.com/datasheet-html/142223/ETC/1page/OZ9976GN.html?lang=en
Have you ever seen a more messed up 'catalog'? (And the PDF download doesn't work.)
The IC manufacturer is http://www.o2micro.com/
Their current catalog pdf does not include the OZ9976. Nor do they seem to have any actual datasheets online.
But the datasheetbank mess does say:

From page 8 of the stupidly dysfunctional online cat:

OZ9976 FEATURES
• Offline Inverter Controller (IPB)
• Supports both fixed and variable frequency applications
• Half-bridge or push-pull topology
• Directly drives pulse transformers
• Dedicated pins for Analog and LPWM dimming
• User-defined minimum operating frequency
• User-defined striking frequency range
• Open-load, over-voltage, and under-voltage lockout protection
• User-defined striking and shutdown delay timers
• Soft start function
GENERAL DESCRIPTION
The OZ9976 is a high efficiency, Pulse Width Modulation (PWM) controller designed
for off line LCD backlight application. It achieves high efficiency power conversion
with minimal switching loss using Zero Current Switching (ZCS) technology. OZ9976
applications can operate under fixed or variable operating frequency with ZCS tech-
nology.
The minimum operating frequency can be set by either an external RC network or
operate in self-oscillating mode. The intelligent operating frequency management
circuitry extends Cold Cathode Fluorescent Lamp (CCFL) lifetime and offers design
flexibility

It appears the word "offline" is code for 'no micro involved', ie analog & PWM control inputs.
Fingers crossed I can use a pot for brightness control.
There is a basic application schematic:


Can anyone find (or have) an actual datasheet for the OZ9976AGN ?  I think I can manage without it, but still it would be nice to have.

[tautech]

There is a download link hidden away not that that dumb datasheet is of much use anyway. 
Attached.

[TerraHertz]

Here's the reply from O2Micro to my inquiry about a datasheet for the OZ9976.

As all of our datasheets are considered confidential, we are unable to provide it to all.

This is what I'd expected. Presumably they sell only to consumer appliance mass manufacturers. And they probably have some kind of confidentiality clauses in contracts. "It's all secret" kind of thing. Even though it's just plain stuff like LED backlighting power circuitry.

[amyk]

They certainly do seem a bit "IP-crazy" if this bit of very strange text in one of their catalogs is any indication...

* NOTE: The OZ9928, OZ9966, OZ9972/72A, OZ9976, and OZ9977/77A/77B are inverter controllers specially designated for use in televisions or applications with
multiple lamps, are warranted and licensed for use in these or any other appropriate applications, and are sold with a license to all relevant O2Micro patents. Sale
of all other O2Micro inverter controllers are subject to the following restrictions: (i) the product is not warranted, indemnifi ed, or licensed for use in televisions or
applications with multiple lamps; (ii) sale of the product and license to O2Micro inverter controller patents are expressly conditioned upon not using this product in a
television or applications with multiple lamps; (iii) by using the product, you agree to notify customers of the limited scope of the license and sale; and (iv) use of the
product in a television or applications with multiple lamps is expressly prohibited, is a material breach of such sale, and violates any express or implied license to any
O2Micro patent. All sales are subject to O2Micro’s conditions and terms of sale and use.

Of course if they do have patents, those should be public anyway