Musical surprise - Page 1
Forum section: electronics / general

author: TerraHertz
author_rank: Super Contributor
timestamp: March 17, 2021, 10:25:40 am
content: 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.)

author: Zero999
author_rank: Super Contributor
timestamp: March 17, 2021, 10:57:57 am
content: 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.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 17, 2021, 12:07:27 pm
content: Quote from: Zero999 on March 17, 2021, 10:57:57 amIf 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 TAS570720-W STEREO DIGITAL AUDIO POWER AMPLIFIER WITH EQ AND DRChttps://www.ti.com/lit/ds/slos556b/slos556b.pdfQuoteActually 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.

author: tunk
author_rank: Super Contributor
timestamp: March 17, 2021, 01:30:23 pm
content: No expert, but for an inexpensive DSO, you could look at the Hantek2000 series which comes with RS232/UART, I2C, SPI, CAN, LIN decoding.http://www.hantek.com/products/detail/17182

author: tautech
author_rank: Super Contributor
timestamp: March 18, 2021, 07:24:36 pm
content: 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.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 21, 2021, 04:40:03 am
content: Quote from: tautech on March 18, 2021, 07:24:36 pmYes, 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.QuoteHa 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 numberCJ6L26.1N1747A1Pretty much the only search result was this nightmare site:http://html.datasheetbank.com/datasheet-html/142223/ETC/1page/OZ9976GN.html?lang=enHave you ever seen a more messed up 'catalog'? (And the PDF download doesn't work.)The IC manufacturer ishttp://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:QuoteIt 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.

author: tautech
author_rank: Super Contributor
timestamp: March 21, 2021, 06:59:03 am
content: There is a download link hidden away not that that dumb datasheet is of much use anyway.Attached.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 23, 2021, 11:40:17 am
content: Here's the reply from O2Micro to my inquiry about a datasheet for the OZ9976.QuoteThis 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.

author: amyk
author_rank: Super Contributor
timestamp: March 24, 2021, 12:33:26 am
content: They certainly do seem a bit "IP-crazy" if this bit of very strange text in one of their catalogs is any indication...QuoteOf course if they do have patents, those should be public anyway