Did I ruin two SXGA+ cables? No: it's the motherboard.

[automobus]

I bought a very beat-up T23 to tinker with. It was described as having a bad screen, and it was cheap, so I thought maybe I could fix it and make a profit. But what a mess it became!

It turns out the panel worked fine, but the picture was pink. I now know that the CCFL backlight is all but dead, but at the time I thought it could be the screen, the cable, or the GPU. This T23 was filthy and cracked everywhere, so I began stripping it and cleaning almost every part. After cleaning it a bit and reassembling it, I find a "white" (pink in this case) screen (every pixel is clear, backlight on). I decided I needed a known good unit, to start testing individual parts.

What I knew so far:
Hitachi screen: works?

So I buy a T23 with SXGA+ and wireless. It has a good LG screen (the first has Hitachi), bright and white. I tested both inverters: both are fine. Then I swapped-in the Hitachi panel from T23#1: still pink, conclude that its backlight is shot, but the pixel matrix is still good.

What I knew so far:
Hitachi screen: works, old backlight
LG screen: good

I have the screen from a VAIO Z1 around. Something went bad on the motherboard (either bridge or Radeon, a lot like what I read about T40). It has a perfect screen, so I try to replace the exhausted Hitachi with the Z1 screen. It is a Toshiba-Matsush_ta SXGA+ panel, and it looks just like the LG panel (screw holes and connector match). I connect the screen to T23#2, and results in a clear backlit white screen (like the Hitachi panel connected to #1). So I say "must not be compatible", and begin replacing the original screen.

What I knew so far:
Hitachi screen: works, old backlight
LG screen: good
TMD screen: "white screen of death" therefore "must not be compatible"

I was going to pack-up T23#2, with its good grade-B screen and everything. It seems to be working well, and I wanted not to break anything in it. Only, I think I already did. I replaced its LG screen, and: "white screen of death". Oh no, I am worried.

I proced to try many combinations of the three screens, two cables, two bases. "White screen", every time.

Where I am now:
Hitachi screen: works? old backlight
LG screen: works?
TMD screen: works? compatible?

Did I ruin two SXA+ cables in one day? Are they that delicate? I stayed up late last night, spending over four hours searching the forum for "LCD cable". Based on what I read, it seems most cables break at the bend, in the laptop fold. There is not that much information out there about broken cables. Both pass visual inspection: I was not using any sharp tools, neither cable is ripped anywhere (that I can tell). Or did I break the connector on all three panels?

What should I do next?

[rkawakami]

My gut feeling says that the LCD cables are probably fine... the problem is with the motherboard. My understanding is that you must use an SXGA+ cable with an SXGA+ screen and an XGA cable with an XGA screen. Mixing them up apparently can cause some damage to the motherboard (blown fuse or other component). I've never used the "wrong" LCD cable when swapping panels on T2x systems but I seem to recall reading in one of the threads here that doing so can be bad. Same goes for using just any old LCD panel. There is a possibility that even though the number of pins and spacing are the same between panels, it's no guarantee that the signals are the same.

[automobus]

Both T23 are SXGA+ units, with SXGA+ cables and SXGA+ screen. Before I bought the perfectly good T23#2, T23#1 developed "white screen". I never connected T23#1 to the VAIO TMD screen (also SXGA+). Yet both ThinkPad original screens, when connected to T23#1, have the "white screen" problem.

Does anyone have an anecdote about damaging LCD cables, or knowledge in general about them? I spent hours last night reading threads that mention a LCD cable, but there really was not much knowledge to be found. Are broken cables common at all?

And a question about the panel connectors: The Hitachi and LG panels were both presumably ordered to spec by IBM, so of course they have the same connector, same position, same pinout. But if the TMD panel (from a VAIO) also has the same connector in the same place, is there not some industry standard behind it? Why would TMD make a screen that fits the same physical requirements as the competition, but use a different electrical pinout?

[rkawakami]

I don't know for sure that a single interface standard exists for a particular screen resolution, given identical: 1) number of pins, 2) pin spacing and 3) the type of connector being used.

[RealBlackStuff]

Look at the mess between T4x and T6x models.
Physically identical screens/connectors, EXCEPT on some T6x LCDs there's a small EEPROM.
A lot of T6x LCDs on eBay are 'compatible with', which means in reality: physically fit, but no eeprom, so do NOT work.
Why would life be any easier in other series?
If T23 LCDs would work in T30, that'd be great. Unfortunately they only FIT... Same with R3x/T3x.
Funny though, R4x works in R5x/T4x, and A3x works in T4x. And T6x works in T4x.
There's no rhyme or reason...

[singbad]

I've replaced quite a few XGA LCDs but I never came across a broken flex PCB cable. I've seen connectors with bad contacts (I damaged one myself) and defective LCDs of course. A white screen could mean a missing voltage or ground contact. But my experience is limited to XGA LCDs in the T30. Things may be different with SXGA.

I'm modifying T30 displays. I've found a way to replace the 298mm-LCDs custom made for IBM by regular 299mm-LCDs. 299mm wide, not diagonal. I just strip the antenna stuff and remove 4 mount posts that are molded into the sides of the display cover. Any $1 LCD from ebay will fit, provided it's 14.1" XGA. The necessary 21mm to 25mm 20pin adapter cables cost me much more ($5 at PCHub)

Best regards,
singbad

[automobus]

I've replaced quite a few XGA LCDs but I never came across a broken flex PCB cable. I've seen connectors with bad contacts (I damaged one myself) and defective LCDs of course.

Thanks!
How do you know if you broke a connector? The very thin circuit board on the LCD has no good test points.

[singbad]

How do you know if you broke a connector?

...bending, moving, applying pressure.

Maybe I had done too much soldering to the connector. I used to make 22mm/25mm adapters myself before I saw them at PCHub. This was my first approach:
http://ftp.nuclear.free.fr/img/LCD/20to30pin.jpg

Then I found I need an additional cable rather than just the adapter since the IBM cable is to short and sits in the wrong place. I decided de-soldering the 20pin connector from the IBM cable and the base connector from the donor display cable. Then I connected the lose wire ends (or the flat cable, depending on display assembly manufacturer) to the end of the IBM cable and fixed my solderwork with epoxy.

http://ftp.nuclear.free.fr/img/LCD/microsoldering.jpg

The pinout of these connectors is always the same scheme (from right to left on photo):

Vcc Vcc Gnd Gnd -Sig1 +Sig1 Gnd -Sig2 +Sig2 Gnd -Sig3 +Sig3 Gnd -Clk +Clk Gnd [ignore the rest...]

Later I found these LCD cable converters at PCHub. I ordered some cables with 20pins/22mm to 20holes/25mm, 100mm cable length.

For those willing to solder: The 20holes/25mm connector is JAE FI-S20S. This is a connector with crimp contacts. It should come pre-wired since microcrimping is much more tricky than microsoldering, at least to me. JAE makes an "LVDS Development Kit":
In order to help support prototype development JAE has introduced a range of FI kits which consist of 2 x crimp socket housings with pre-crimped 300mm leads. The number of leads included is appropriate to the number of contacts in the housing.

Seen for $14 at Digikey and RS Anybody seen something similar or single pre-wired connectors for less?

Best regards,
singbad

[automobus]

My gut feeling says that the LCD cables are probably fine... the problem is with the motherboard.

It is the motherboard.

The not-compatible screen is (TMD) Toshiba M a t s u s h i t a LTD141EM1X. This panel, connected to a T20-family ThinkPad, will blow fuse F4 on system board / planar.

I have planar / motherboard 30L2228 FRU 26P7997.

Fuse F4 is in front of display connector pin 56, tiny, black, marked only "N". Thank you very much, RealBlackStuff, for helping me. He directed me to document "Thinkpad T4x Board Fuses" theboardroom.info/T4x_Fuses.pdf. Apparently, this is SCHURTER USF 0603, Surface Mount Fuse, 1.6 x 0.8 mm, Super-Quick-Acting FF, 32 VAC, 32 VDC, 2 A (http://www.schurter.co.uk/var/schurter/storage/ilcatalogue/files/document/datasheet/en/pdf/typ_USF_0603.pdf).

2015-06-19: Ray teaches me, fuses F4 & F5 are Littelfuse 434002 2A/32V fast blow.