How to make LVDS test under 99 cents

[Peter Chiu]

How to make LVDS tester under 99 cents.

I feel a little cold out here........No problem.... Let's ...R..O..C....K....

Background music: John Lennon
https://www.youtube.com/watch?v=fi7gs9MuNbc

Instead of buy another junk...and all I want to know is...TV has LVDS signals ............YES or NO.......That's ALL..I don't care how many pairs.. LVDS signals TV has..........so...... that's find out..... HOW.......have ...FUN....

JUNK:
http://www.ebay.com/itm/LED-LCD-Pane...-/111081281772

http://www.ebay.com/itm/LVDS-Panel-T...-/271543998313

............................I hate all that cables..... i already burn two LCD screens by putting wrong LVDS cable......^%#%$&*%......






Figure 1 illustrates a typical LVDS transmitter. This transmitter consists of <<<<<<<<<a current-mode driver, which provides around 3.5 mA of current through the transmission lines of the differential pair. >>>>>>>>>>>>At the receiver, a 100 Ω termination resistor is used to match the impedance of the transmission line that connects the receiver to the driver. Closely matching the impedance of this termination resistor with the impedance of the transmission lines reduces harmful signal reflections that decrease signal quality. The termination resistor also provides a path between the complementary signal paths of the system. The high input impedance of the receiver causes the 3.5 mA current coming from the driver to flow through the 100 Ω termination resistor, resulting in a voltage difference of 350 mV between the receiver inputs. As the path for the current within the driver changes from one path to another, the direction of the current flowing through the termination resistor at the receiver changes as well. The direction of the current through the resistor determines whether a positive or negative differential voltage is read. A positive differential voltage represents logic-high level, and a negative differential voltage represents logic-low level.

The standard defines the input voltage range of the receiver, VIN, to be 0 to 2.4 V. This input voltage range is significantly larger than the range of expected voltages from the driver. This difference provides the ability to absorb and reject common-mode noise, noise that is present on both lines of the differential pair, and allow for offsets between the driver and the receiver


reference:
http://www.ni.com/white-paper/4441/en/


This is the one..... we gonna use....

a current-mode driver, which provides around /////////3.5 mA///////// of current through the ////////transmission lines ///////of the differential pair.

My first thread .....I don't know how to correct the misspelling on the top..
Should be:::How to make LVDS ....test.er...... under 99 cents.

[Peter Chiu]

Re: How to make LVDS test under 99 cents

The increase in applications using LVDS has led to a growing need to test LVDS-based applications. One approach to test LVDS devices uses a device with a dedicated FPGA that can be programmed to generate or analyze test patterns for a device under test. Using this approach, a test developer with expertise in programming FPGAs must program the device to generate or acquire the desired test pattern. This approach offers flexibility in that the functionality of the tester can be modified by reprogramming the FPGA to perform the desired operations. However, there are significant challenges with this approach. FPGA designs are typically application specific and require significant investment in correctly using them in the field. Requiring many man-hours to design, develop, test, validate, and implement, an FPGA may not be an efficient use of test engineering resources.

Another approach to designing an LVDS test system is to use a modular instrument solution based on an open standard, multivendor platform such as PXI. With PXI modular instrumentation, you automatically benefit from the low cost, ease of use, and flexibility of PC technology. Recently, the releases of the PXI-6561 and PXI-6562 digital waveform generator/analyzer devices by National Instruments have provided a modular solution for testing LVDS devices. Familiar industry-standard measurement and automation software such as LabVIEW and LabWindows/CVI can be used to control the PXI digital waveform generator/analyzer devices to implement the desired test. Time-saving software tools such as the NI Digital Waveform Editor can be used to edit existing test patterns and create new test patterns as well as view acquired digital waveforms. New waveforms can be created using fill patterns for common test patterns such as pseudorandom bit sequence (PRBS), reducing the amount of time and expertise required to design and program a quality LVDS test system. Furthermore, because these devices share a common Synchronization and Memory Core (SMC) architecture, they can be tightly synchronized with each other, to form a scalable solution in which channel count can be conveniently expanded as necessary.

https://cdn.badcaps-static.com/pdfs/...c068d64d67.pdf

We don't have that kinda of money .........How should we do ....get a loan.....or
We just try to give life to the junks in landfill.......

Ok waveform is up to 200-400m hz .....from I read is up to 1g hz..(bits /s).....HF means money...
http://www.ni.com/modularinstruments/
http://www.ni.com/vms/
http://www.ni.com/virtualbench/ .......... I real love this one......

[budm]

Re: How to make LVDS test under 99 cents

"I hate all that cables..... i already burn two LCD screens by putting wrong LVDS cable......^%#%$&*%..... "
Why did you not study first? Simple logic, start using what you learn in school. LOGIC AND COMMON SENSE IS YOU BEST TOOLS.
Again I hate to burst your bubble, the pinout of the LVDS connectors are not standardized, you need to get the LCD panel spec to get the pinout or the mother board diagram to find out which the function of each pin.
You should at least download a LCD panel spec and main board circuit to at least understand what it needs to function and how it function before rtying to test, otherwise you will end up damaging VERY EXPENSIVE T-CON board or the panel if the T-CON is integrated into the panel assembly.
Differential signal sending and receiving is nothing new, it has been used in other application for decade, in this case for TV, it is just LOW VOLTAGE DIFF SIGNAL.
In case you did not study the basic of signal transmission and receiving, differential signaling is used for noise immunity in Ethernet, RS-485, CAN and USB. It is also used in professional audio system. OP-amp has diff input.

This is what you can do when you have an info:
https://www.badcaps.net/forum/showth...ght=t-con+hack

My suggestion, try to understand how thing works first so you will know how to solve the problems and know how to modify it to do something else.

[Peter Chiu]

Re: How to make LVDS test under 99 cents

Believe or not ....same model NO....but different LCD screen Panel....late, I found out from shopjimmy they use 4 different penals......make this world much complicated...

[budm]

Re: How to make LVDS test under 99 cents

You just found that out?

That is common practice for TV manufacturers and panel maker, they can make the same model but different versions will have different connection and most of all the running Voltage, version one may use 5V, version 2 may use 12V, different pin assignment.
I spent lots of time doing research and reverse engineering.

[Peter Chiu]

Re: How to make LVDS test under 99 cents

The device.... we try to built is foolproof..... Just like Ur remote controller close to the cable RED LED blinks and ...Beep.. Beep... and U know LVDS is working ...U can't test unplugged LVDS cable...no current.....

But for under 99 cents is.... U got to have same junks as I do.....


First we junk one speaker take the copper coil.... U could use all ...but I like take out some of the coil out just leave about 2-3 mm look more nice....then U have ..........a current detector......

Tips:
kept rest the cooper wires .....Best jumper wires to fix broken tiny circuit board....
Case 1:
I did fix one 73'LED tv with broken remote power board ....the TV won't come on ..SORRY.....I did charge them...$450....and I show them what I need to do ....need to use my Stereo microscope to solder....they say no problem....until now, I till feel guilty.....but If I broken the screen I need to pay them $3000.00..... at that time..and I don't think my insurance will pay for it.......And I am at (second opinion) anyway....


Next see if U can find any OP AMP........

[budm]

Re: How to make LVDS test under 99 cents

"U can't test unplugged LVDS cable...no current....."
You can look just at either + or - of diff signal to see it is present or not, no need for current loop, what are trying find is the signals are present or not, but the key part about LVDS for the T-CON IS THAT THERE ARE 4 LVDS signals! and sync signals, for all four LVDS signals to failed at the same is very not likely unless the LVDS signal IC is dead due to no VCC or completely failed IC.
You want to learn? Use your scope to look at either + or - of the diff signal with ref to GND and see it for yourself.
Have you ever look at the circuit to see how it function?
Another clue for you, signal HARMONICS!
You have scope, right?
Assignment for you, get a working TV, spec sheet of the LCD panel , then remove one LVDS signal one at at time, all at the same time, sync signals one at a time, all at the same time and see what effect you will see on the screen and tell us what you see so we do not waste our time in this thread.
Is that logical to you?

[Peter Chiu]

Re: How to make LVDS test under 99 cents

this one has 5 pairs LG_50PC5DC_50PC5D_PA-73E

but..... now I work on LED LCD LG 55ln5400 has 10 pairs LDVS (51Pin LVDS Connector) 10 bits (10 pair signals) on flat cable ..... Tom only have this one newer LG_LA21B_55LS5600-UC_[SM].....................over Page 34

Which I try to do is ( look the mother board is small.) just use as a test Jag
I will make adapter to switch to Samsung or other brands.....I think newer LED LCD screen all has at least 10 pairs LVDS signal...Hard to find any Data....I don't want burn any screen again.....
http://www.ebay.com/itm/NJYMST6M30-V...-/271123027434
http://www.ebay.co.uk/itm/FI-RE51-LV...-/271204538983
A 5 pairs B 5 pairs then switch because some tester say 55' can display only half the screen..

I would like to test each one as Ur suggestion.
Don't worry, I will find older 32' TV and find out ...

The last picture ...we need to change HDD for customer HP desktop (windows 7)

[Peter Chiu]

Re: How to make LVDS test under 99 cents

LG_LA21B_55LS5600

P703 LVDS connector FI-RE51S-HF-J-R1500

(Vcc) 48 49 50 51
(ground) 52 46 45 44 43 42 37 34 26 21 18 11

8 pairs LVDS signal (10 bit)


same pinlay out to
pinouts of LC470WUD-SBT1 LCD panel:

This type LVDS cable is suitable for panels ≥ 26”, for resolution 1920*1080 HD LCD panels.
Compatible with LG, AUO, CHIMEI, Sharp panels.
Panel size (inch)
Brand
Model no.

AUO T370HW04 V4
LGD LC370WUN-SAB1
LGD LC370WUN-SBD1
LGD LC370WUN-SBA1
SHP LK400D3LA14
AUO T420HW02 V0
AUO T420HW04 V2
AUO T420HW04 V0
AUO T420HW04 V001
AUO T420HW04 V7
AUO T420HW04 V8
AUO T420HW06 V3
AUO T420HW06 V2
AUO T420HW06 V1
CMO V420H1-L05
CMO V420H1-L07
CMO V420H1-L11
CMO V420H1-L15
CMO V420H2-L01
LGD LC420WUN-SAA1
LGD LC420WUN-SBD1
LGD LC420WUE-SBA1
LGD LC420WUN-SBA1
LGD LC420WUN-SBD2
LGD LC420WUN-SCA1
SHP LK460D3LA28
LGD LC470WUN-SAA1
LGD LC470WUE-SBA1
LGD LC470WUN-SBC1
LGD LC470WUN-SBC2
SHP LK520D3LZ18
52<, /D, IV>
SHP LK520D3LZ13
55
LGD
LC550WUN-SCA1

http://www.njytouch.com/products/150-en.html

Thank you, UR research and reverse engineering.

I will order this to play around...I got new toy.....
http://www.aliexpress.com/store/prod...861122957.html
TIPs:
I put some leds if match the vcc and ground pin maybe ok to test with...

[budm]

Re: How to make LVDS test under 99 cents

This is one of the place I use to get LCD panel spec:
http://www.beyondinfinite.com/library.html
http://www.spectrah.com/product/

As you can see there are lots more than 3~4 companies that make LCD panels.

[Peter Chiu]

Re: How to make LVDS test under 99 cents

Thanks for Ur informations:

Compaq laptop LVDS test report:

background music:
https://www.youtube.com/watch?v=rNsgHMklBW0


Panel No: B156XW02 V2

a TFT LCD panel,
a driver circuit, and LED backlight system. The screen format is intended to support the 16:9
HD, 1366(H) x768(V) screen and 262k colors (RGB 6-bits data driver) with LED backlight driving circuit. All input signals are LVDS interface compatible.

(EDID).......Extended display identification data
is a data structure provided by a digital display to describe its capabilities to a video source (e.g. graphics card or set-top box). It is what enables a modern personal computer to know what kinds of monitors are connected to it.

reference data :



Sorry , my LVDS connector fired (burned)( and only have DC12v).....I can't do it .....any more.....Wuu....(*^(%^(^%)*..........If this is 120' TV at customer's home .....they call 911 right away....

[budm]

Re: How to make LVDS test under 99 cents

"Sorry , my LVDS connector fired (burned).....I can't do it .....any more.....Wuu....(*^(%^(^%)*..........If this is 120' TV at customer's home .....they call 911 right away...."
Did you verify the VCC and GND pin out first?

[Peter Chiu]

Re: How to make LVDS test under 99 cents

I did and I copy the AUO LVDS pinout held in my hand ,VCC PINs38...39..40 on right corner which has a big hole now. Don't worry. Wanna lean gonna pay for tuition.

[budm]

Re: How to make LVDS test under 99 cents

What is the VCC voltage you fed the T-CON?
It requires TWO power supplies: VDD and VLED, and correct power GND pins (VSS GND, and VLED GND).

[Peter Chiu]

Re: How to make LVDS test under 99 cents

I did come to office Sunday afternoon.
Do the lab but pictures real bad,because I look like monkey one hand on scope other hand on camera and need to push the menu button.

RCA 40LA45RQ
panel No.:V400H-L10 Rev c8

http://www.ame.cz/LCD-panel-40-V400H...379_10699.aspx

I did have some harvest (Look the pics) when I push the menu button... the waveform change....the waveforms more dense.

What I'm Trying To Say: By that diffidence waveforms....... can we detect and invent (The non contact LVDS waveform tester).

[Peter Chiu]

Re: How to make LVDS test under 99 cents

This is 15.4" LED LCD screen for laptop
Vdd= 3.3V
VLED= 12v

I did unplug the LVDS cable to do next project .....and I did saw the waveform then I moved the probe and happened....... but near the pin-out of V is no connection(NC)

[budm]

Re: How to make LVDS test under 99 cents

When you use the scope, since we have high Voltage for the CCFL that radiate noise like crazy and you scope will easily pick up the high voltage, and the signals we are trying to see is in mV range, you should look at the signal when the backlights are on and then try it again without having the backlights on (by either disconnect the cable to the inverter board or disable the BL-ON signal).
Also use the video source that changes the scene all the time instead if still image, look at the score and the image on the screen then you should see the change on the scope when the Video images change.
BTW, the scope probe Ground lead should also be as short as possible.
You can try connecting the scope probe GND lead to the tip of the scope probe and move the probe around, you will see that the scope will pick up the radiated signals, that little loop will act as an antenna loop, that is why the GND lead has to be as short as possible.

http://emcesd.com/tt070199.htm

[Peter Chiu]

Re: How to make LVDS test under 99 cents

What I'm Trying To Say: By that diffidence waveform....... can we detect and invent (The non contact LVDS waveform tester).

Nobody want built from OP AMP. So I think another way...

A current detector+ESR meter (modified)......I will give U answer tomorrow.

I gonna use this one
http://www.geocities.ws/podernixie/ESR/index-en.html

http://electronics-diy.com/electroni...ic.php?id=1010

Look here .....CIRCUIT DESCRIPTION ... maybe I can modify something..

If I push menu button , the 1 MA meter move a bit ........

Old Tips : ESR meter is a good coil ring tester( we used ESR meter to test tv deflection yoke)

[budm]

Re: How to make LVDS test under 99 cents

All we want to find out is that there are activities form the main board or not since once in a while we get the TV/monitor what shows no image on the screen even though all the Voltages (12V, 1.8V, 3.3V, 5V, etc) on the T-CON are present so we just need to find out if the main board even sends out any LVDS signals or not.

[Peter Chiu]

Re: How to make LVDS test under 99 cents

The main board or T-con sometime has test-point can test,but 4k or higher resolution tv .....bit/s rate is up to GHz ...100m hz scope would not see too clear . And the connector is too tiny to probe them.

[Real case] : 55' Samsung LED TV won't can on , unplug power cable to mother board , back light come on, change mother board and T-con still not work , open the LCD screen ......clean the water stains still not work.......dog TV.....both scope and LVDS tester won't help, too.....

If someone make a handheld device that can converts high resolution down to low resolution to a 3" LCD screen..... will be great...I could finish my troubleshooting in 10 min instead of waiting the parts came....