Clevo P1xx series LVDS soldered, why?

Can anybody explain to me why the 4th and 5th pin on the LVDS connector are soldered together?

Whats the reason behind this? Why not leave it as is?

 

Depends on what kind of LVDS cable it is, but it's probably just shorting 2 ground connections together (in case it's not run on the PCB or vice-versa).

 

Not a LVDS cable, the actual slot on the PCB.

 

Yes, but the slot just routes the traces to the cable, the lines effectively continue in the PCB is the way to think of it.

 

I've seen these soldered pins now and then too, but it's quite rare. The panel manufacturer did this, so if you look up the panel's specification sheet then you'll know if it's indeed combining voltages or grounds, as Stooj mentioned, or whether it's grounding one of its function pins, disabling the feature in a rather crude manner. Make sure to count using the soldered pins on the connector, not the wires; the first and last wire are usually unpopulated (reserved for factory use).

edit:
A photo would make things clear for anyone that hasn't seen this before. Have a few old LVDS panels lying around, but none had any of its pins soldered together.

 

If it's a solder bridge then it's often done on the PCB. Achieves the same thing.

Typically it's only done to accommodate changes they weren't aware of when the PCB was printed (ie a new panel with different pin-out), or even a mistake in the original run. It's cheaper to bridge the connection than re-do all the PCBs.
Chances are it's a new panel or new pin-out that got used as the LVDS connector specs I've seen are all different and somewhere around 30% of the pins either do nothing, "reserved for future use" or ground links.

 

EDIT:

 

Ah, but that's the motherboard side; the pin arrangement will be different from that of the panel. It's probably for the same reason Stooj has mentioned, except relating to a motherboard in this instance. You'd need the mb schematics to find out their purpose or use a multimeter set to resistance and measure between the soldered pins on the mb and each pin on the inserted cable at the lcd end. When it drops to zero then you know the matching pin of the lcd and once again the panel specs will tell you their purpose.

There's one other possibility; modern pcb soldering is done on an automated production line and with automated testing (that's what the exposed copper dots on the pcb are for). Here's a complete cycle with smd, through-hole, a manual step and the final testing stage:



If there's a small soldering error (such as bridged pins) anywhere in the process then no one would find out or even care as long as the automated tester said ' all systems are go'. This would be the case if these particular pins are both voltage, both ground or one of them's a non-functioning pin. A motherboard is quite large and such mostly-cosmetic defects are rare, but if you take a smartphone apart then there's quite often one or two components soldered askew. Any board that didn't pass the test would've been repaired manually or trashed, but those with small defects will happily exit the factory and end up in the hands of a consumer.

 

It's not an error, since all P1xx clevo models have this.

 

Hmm ... then it's not a random, one-off error, but something that was fixed after the pcb's design was completed. A simple bridge would've been far more cheaply solved in the board than with a manually-added blob of solder.

Did find the comment that goes with this addendum, but it's in Chinese (of course):

Roughly:

It's pins 7 and 9 that are soldered together, but if you want to know their original purpose then you'll have to use that multimeter trick. Then you'll know which pins they correspond to on the display and the function that was shorted.