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Electronics DIY LVDS controller - all soldered, no video?

Discussion in 'Modding' started by PsychoI3oy, 23 May 2004.

  1. coorz

    coorz Miffed

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    I'd say crosscheck the grounds with a multimeter, see which scheme matches.
     
  2. PsychoI3oy

    PsychoI3oy Minimodder

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    doh, therein lies another problem, my multimeter blew it's fuse testing the mA of a rechargable drill battery (obviously higher than 350mA) when i was thinking of using it to power the ccfl inverter.

    but that does sound like the safest bet, thanks
     
  3. SteveyG

    SteveyG Electromodder

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    :eyebrow: Never connect an ammeter across a power supply. Rechargable batteries have a particularly low impedance which is why you blew your fuse...

    However, since you're only wanting to use the continuity tester, just temporarily wrap some wire round the fuse holder. I suggest you check continuity between each of the pins of the IC and the pin on the connector it is meant to be connected to. Remember to remove the wire from the fuseholder to prevent you causing damage should you attempt to measure the current that your multimeter wires can carry before glowing orange :duh:
     
  4. woodshop

    woodshop UnSeenly

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    by lacking i ment that the pcb seemeb a little to simple to work (from all the stuff i've herd about controlers csting 200-600 bucks. i mean it's one chip and no caps ot resistores or nothing.

    (but what do i know!!) i hope you get this thing working. subscribed (forgot the last time thats why my reply took so long.
     
  5. PsychoI3oy

    PsychoI3oy Minimodder

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    ok, i was a bad boy. i didn't feel like going to radio shack for a replacement fuse, so i just shoved a piece of desoldering braid in there with the fuse to short it. the multimeter now works :)

    i tested both voltage differential between case ground and pins on the VESA header, and resistance between case ground and pins.

    labeled here as (top row) y1-y13 and (bottom row) as z1-z13 (as in this lovely ascii diagaram):

    Code:
    ------------------------------------------------------------ -----
                  Y1               J2                  Y13
                 +---------------------------------------+
                 | .  .  .  .  .  .  .  .  .  .  .  .  . |
                 | .  .  .  .  .  .  .  .  .  .  .  .    |
                 +---------------------------------------+
                  Z1                                    Z13 (pin missing)
    ---------------------------------------------------------------------
    (stolen from here: http://www.epanorama.net/documents/pc/vga_feature.html)

    pin -> ground voltage:

    y1-y9 & y11-13: 0v
    y10: 2.5v

    z1-3 & z8-10: 0v
    z4-z6: 2v
    z7: 5v
    z11: 3v
    z12: 5v

    pin -> ground resistance:
    y1-y12: ~2k ohms
    y13: 0 ohms

    z1-3: 0 ohms
    z4-7: ~2k ohms
    z8-10: 0 ohms
    z11: ~2k ohms
    z12: 0 ohms


    meaning.... the pinout in the above link is probably accurate, though i'm not sure why the voltages vary on z7, z12 and z13, but those are specifically not used so i don't care. and looking at the response above pointing this link out:http://inf33-www.informatik.unibw-muenchen.de/infothek/computer/tutorial/eprmhtml/eprm/268.htm , if the pins are numbered 2 4 6 8 across the top row (y in my case) then the top pinout on that page is also accurate.

    egads, why can't people just standardize how they label pins?

    anyway, i'm off to rewire the connection between the video card and chip, hope i didn't fry anything.

    oh, one last thought. on a flat ribbon cable, the pinout would be such that the cable will be data/ground/data/ground/etc. except the middle pins (enable internal stuff). i know high speed SCSI and ATA and ethernet use ground between signals to prevent crosstalk. does anyone see anything wrong with me using a rounded floppy cable instead of the flat one i've already mangled? the data lines won't be seperated by ground, but the floppy cable i have is longer and shielded (and UV blue, IIRC) and would just be easier cause then i could rip the other cable off and not have to use it.

    i'mma start desoldering then check back here to see what anyone has to say...


    edited to add: this post was typed out about 15 minutes before i actually hit send, i had clicked preview and forgot to actually send it, so my shorting of the fuse in my multimeter etc was a crosspost with the suggestion above


    edited a second time to add: well i'm a tard, the above question about flat vs round cable is moot, the flat cable i was using is missing a couple wires (which were previously N/C but now that i have the real pinout, are rather important)

    rounded chopped floppy it is...
     
    Last edited: 9 Jun 2004
  6. PsychoI3oy

    PsychoI3oy Minimodder

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    i'd say the biggest reason the spensive controller cards cost so much is that they have to support a wide range of lcd's and i believe most of them are also video cards in and of themselves. this is why they have so much circutry on them.

    in this case my card is taking from another video source and converting to lvds and only has to work with the lcd I have, which happens to have the sister chip to mine inside it. my card would most certanly not work with any lcd that didn't have a TI FlatLink LVDS reciever chip inside it, and probably wouldn't work with some of the ones that do.

    make sense?
     
  7. woodshop

    woodshop UnSeenly

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    makes sense. so if i got you right from what you just said is when you removed the lcd tou sook the chip that did the conversion from the videocard in the lappy to something the lcd could understand. so what your now trying to do is reconstruct what was on the lappy mobo on another pcb.. correct. So basicly when this works you will just use your second video port to get the screen.
     
  8. PsychoI3oy

    PsychoI3oy Minimodder

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    basically :)

    i'm sure the reality is much more complex than that, but wen it comes down to it, i'm just connecting outputs to inputs and praying.
     
  9. PsychoI3oy

    PsychoI3oy Minimodder

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    well, to save myself the typing, i'll just copy and paste from the chat room i'm in:

    <PsychoI3oy> should this work at this point, i'll have a nice (albiet backlight-less) 13 inch tft for my celeron box
    <PsychoI3oy> should it not work, i fear i may have a smouldering pile of electronics
    <PsychoI3oy> no idea
    <PsychoI3oy> :)
    <PsychoI3oy> ok, bbiab
    <someone else> get the fire extinguisher handy
    [15 minutes later]
    <PsychoI3oy> hrmm
    <PsychoI3oy> how bout neither?
    <PsychoI3oy> no smoking pile
    <PsychoI3oy> no video on the lcd
    <PsychoI3oy> same thing it was displaying before, the slightly aqua screen with odd white dots along one side
    <PsychoI3oy> hooked up a normal monitor to the video card and it's still working on VGA out, at least
    <PsychoI3oy> tied 'enable internal sync', 'enable internal video', and 'enable internal dot clock' to +5v, ground, and left them unconnected
    <PsychoI3oy> no dice
    <PsychoI3oy> tied 'enable' on the chip to +3.3v, 5v, and ground, and unconnected, no dice
    <PsychoI3oy> and as many combinations of those 2 as i care to remember
    <PsychoI3oy> nada
    <PsychoI3oy> as if the chip wasn't even turned on/sending signal
    <PsychoI3oy> now, i don't know if it is turned on
    <PsychoI3oy> i don't know if it's fried
    <PsychoI3oy> i don't know if it's getting data from the video card
    <PsychoI3oy> and i really have no way to test any of these things
    <PsychoI3oy> oddy combinations of those 2 as i care to remember
    <PsychoI3oy> nada
    <PsychoI3oy> as if the chip wasn't even turned on/sending signal
    <PsychoI3oy> now, i don't know if it is turned on
    <PsychoI3oy> i don't know if it's fried
    <PsychoI3oy> i don't know if it's getting data from the video card
    <PsychoI3oy> and i really have no way to test any of these things
    <PsychoI3oy> odd

    well i pretty much said it up there. i hooked everything up the way i think it should be, according to my schematic and the correct VESA pinout, and tried a few things, and nothing's working.

    about the only other thing i could test at this point is the video card, i have a voodoo3 3500tv with a vesa header on it, but i don't feel like digging for the big purple pod thingie to connect it to a normal monitor.

    any suggestions? anyone?
     
  10. star882

    star882 What's a Dremel?

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    Hook up a regular monitor for debugging, then try playing with the settings in the XF86config file.
    Use http://www.linux.org/docs/ldp/howto/XFree86-Video-Timings-HOWTO/index.html for a guide.
    BTW, if a timing you tried is such that neither the monitor nor the panel works, jump back to the command prompt with Ctrl+Alt+F1.
    Note: Since each timing period must be manually set, XFree86 3.3.6 is probably the best to play with.
     
  11. PsychoI3oy

    PsychoI3oy Minimodder

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    heh, i'm not even close to there yet, i'm still trying to get it to show the bios post telling me the hard drive isn't plugged in. if i'm lucky i might be able to get a framebuffer console or something, but getting X up and running on it is a far way off. though that does bring up the question, does the VFC even start shooting video out at that early stage of the game? i'd think so cause the original purpose was internal passthrough for other cards, such that you'd have the monitor plugged into another card. but who knows, maybe i'll try it with everything plugged in and actually get to a linux console (doubt i bothered enabling framebuffer console, i tried to make the kernel as lean as possible, IIRC) and see if it works there.
     
  12. star882

    star882 What's a Dremel?

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    The problem is, the default configuration used by the BIOS most likely doesn't have the right timings.
    So therefore, you would have to edit the ROM on your card (good luck!) or forget about using the LCD until X comes up.
    BTW, I can help you with the inverter if you post nice high resolution pictures of both the front and the back. A shot of the cable end itself won't hurt, either.
     
  13. PsychoI3oy

    PsychoI3oy Minimodder

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    i actually had a brainstorm about what to connect the mysterious 4th pin of the CCFL to, i think it needs to go to +5v or +3v to turn on the transistor that the power goes through. anywho, that's nearly a moot point as the lcd don't work, but i have a friend with a high sensitivity digital multimeter that he may let me borrow this weekend, so i can tell wether or not i'm getting signal from the VFC (i could have blown it when i had it wired wrong) and if so, wether or not the chip is transmitting lvds signals, etc.

    but that will have to wait till tomorrow, friday, or this weekend, etc.

    but thanks for the offer, i'll throw some hi res (and hopefully not blurry) pics of the inverter board up tonight or tomorrow.


    the other thing i was thinking, if i did blow this chip and/or the lcd itself, I do have a (fully functional) nearly identical laptop to the one i got this screen out of (only processor speed is higher, and this one actually has a hard drive and ram and working keyboard, most of which scalped out of the laptop this LCD came out of) and if this whole theory about using the lvds chip is actually practical, i could make a second circuit board (better this time) and redo everything with the second chip, lcd, and cable.

    but i haven't given up on this one yet (though i do have a plan for the backlight diffuser if i don't get it working :idea: ) and thanks for all the support guys
     
  14. star882

    star882 What's a Dremel?

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    Open up the other laptop, then turn it on and probe the circuits (do this for the inverter first, as it's much easier).
    This will make things much easier.
    Oh, and even if the LCD doesn't work, you can still take out the CCFL and inverter and use it as a case light.
     
  15. PsychoI3oy

    PsychoI3oy Minimodder

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    will do tomorrow, bedtime now (work sucks)

    oh, and i might use the (white) ccfl from the laptop and the inverter, but what i really want is the diffuser screen that takes the single CCFL and spreads it across the whole screen.... for something else in my main case.... linked below.... i'll let you figure it out (hint, it'd be an orange ccfl that i'd be diffusing)
     
  16. Nezuji

    Nezuji What's a Dremel?

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    Hi,

    Sorry for reviving such an old thread, but I was looking for just this sort of info and where else should Google turn it up but at bit-tech.net!

    Anyway, I've been reading about home-made LCD projectors lately, and looking lingeringly at my poor old Armada 7400 that I've killed slowly over the years, but which still has a fully working screen. Problem is, in order to make a projector out of it, I've got to get the LCD itself out of the screen cover. Does anyone know if this is this possible? There are two screws below the LCD panel; I've removed them but the enclosure won't be opening without quite a bit of force. The fact that there are screws there at all seems encouraging to me, but I still suspect that the screen is intended to be replaced whole as one big unit.

    I've also got a question about the inputs. On the schematics linked to in this thread (very useful!), it looks like -- with three high-frequency ADCs and a little glue logic -- I could plug a VGA signal straight into this puppy. Am I being naive?

    Any help or comments appreciated!

    Nezuji :)
     
  17. Sea Shadow

    Sea Shadow aka "Panda"

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    Ok regarding the removal of the LCD, look for rubber pads on the frame encasing the LCD, they like to hide the screws behind there, also look for circular pieces of plastic that look like they were just stuck in the frame around the LCD, there are likely screws behind those too. Hope that helps :thumb:
     
  18. Nezuji

    Nezuji What's a Dremel?

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    The two screws I removed were originally hidden under little rubber pads. I couldn't see where any other screws might be hidden, but I'll have another look tonight in case I missed some. Thanks for the advice.

    Nezuji :)
     
  19. Nezuji

    Nezuji What's a Dremel?

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    EDIT: I take no responsibility for you ruining any equipment or suffering any injury if you attempt anything I've outlined here or in any subsequent posts. It is up to you to take any necessary precautions at all times.

    On the offchance that this helps anyone, I gave up being delicate (trying to keep it usable in its original form) and just went as forcefully at ripping the thing apart as I dared (didn't want to break the LCD). I found that:

    a) The lighter grey section on the lid is just stuck on and comes off relatively painlessly. Behind it is a largish hole covered with (presumably) EM-shielding foil. This might be helpful in the later stages of getting the panel out of the case.

    b) The other screws were hidden on the inside of the lid (the viewable side). Around the LCD, there's edging which looks like a solid piece, but is actually just a thin plastic sheet (the part with "Compaq Armada 7400" printed on it) glued in the same way as the bit on the outside. The best corner to start prying it off from is probably the top right. Underneath the plastic in that corner, there's a 1-1.5cm margin of solid case where you can get some good leverage with something thin (I used a simple pocket knife blade) without risking damage to the LCD.

    I'll try to borrow a digicam from a friend and take some shots of however far I get (I have a habit of giving things up before finishing them :p)

    Nezuji :)
     
    Last edited: 6 Jan 2005
  20. peterfnet

    peterfnet What's a Dremel?

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    Hello all,

    I'm looking to revive this topic. Many things have changed since our last attempts.

    first of all, TI now barely recognizes the SN75LVDS84, but does for the SN75LVDS83. There is a datasheet for the 2nd that is provided by TI. The first does not.

    They both are Flatlink(tm) Transmitters.

    I will be doing some personal development and research on this. Who knows, if this works out, I'll use this for my Electrical Engineering Senior project.

    Maybe i will be just talking to the wind, but if you're at least still reading this topic, let me know!! :worried:
     
    Last edited: 7 Jul 2006

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