GW Instek LCR-821 LCR Meter Display Issue.......

[Smokey]

I scored a GW Instek LCR-821 LCR Meter from the ebays...

Product page (discontinued)  = https://www.gwinstek.com/en-US/products/detail/LCR-800
DataSheet = https://www.gwinstek.com/en-global/products/downloadSeriesDownNew/13514/766
Manual = https://www.gwinstek.com/en-US/products/downloadSeriesDownNew/13505/769

...It appears to be working except for a few lines on the LCD display that are out:


A quick teardown showed no obvious problems and reseating the display ribbon cables had no effect.

The display itself is a pretty big big module with a sticker and the following part numbers:
"13031101D129"
"LMBHAT014G18CS"

Searching the last number turns up what looks like the same thing from an aliexpress seller for $62
https://www.aliexpress.us/item/3256803247659429.html


So that's the story and the extent of the research I've done so far. 
What do you think?  What would cause just a few lines like that to go out?  Any hope of fixing this one, or should I just try the aliexpress replacement and see what if anything shows up in the mail?

[KungFuJosh]

The original LCD on the Hioki 3532-50 that I'm repairing also had a few lines missing, and a bad backlight. The easiest thing to do is to replace the LCD, assuming you get a good replacement.

If the seller's feedback is good enough, it's probably worth a shot for $62 as long as they accept returns if it doesn't work.

[nctnico]

It is possible there are a few bad solder joints on the display module's board (the row driver chips) or that the conductive rubber contact strips between the board and the screen itself are no longer making contact. What you can try is to take the display module apart and clean de PCB and conductive rubbers with alcohol. Just make sure to have room on a clean desk to lay out all the parts of the display.

AFAIK this display module is pretty much self contained so any problem with the display module is most likely from the display module itself.

[Smokey]

... Just make sure to have room on a clean desk to lay out all the parts of the display....

...you ask a lot of this poor engineer....

[Smokey]

wow.  that was fast... Bing search already indexed this thread.. so my bing search for "LMBHAT014G18CS" points me back here as the top result...

[Smokey]

PSA:  Don't take apart a "LMBHAT014G18CS" display module

Well that didn't go as planned.  There is definitely a seriously high pin-count zebra strip along the top of the display... but..

There is also this strange really thin cable on one side that appears to have been bonded to a row of pads on the display board.... I'm pretty sure this isn't going back together...   
I'm actually not sure how they even assembled it since you sort of have to drop the board straight down to get the metal tabs to allign, but this cable would need to be folded over.

[KungFuJosh]

Well that didn't go as planned.

That's also my experience with repairing bad LCDs. 🤣

Replacement is soooooooo much easier, as long as an equivalent product is available.

[Smokey]

... I guess I could solder about 1000 kynar wires between the cable and the board.. good thing I have a clean area of bench ready

[KungFuJosh]

Start now, and you might be half done by the time the new LCD comes from China. 😉

[Smokey]

wow.  I reassembled the display and it actually does something! 

unfortunately that something is having even more dead rows than it did when I started

I guess I'll take one more shot at aligning everything.

[Smokey]

..well I'm not ahead.. but I'm not as far behind as I was a minute ago.
More dead lines than when I started but not as many as the worst go.

I'm pretty sure what I thought was "bonding" of some sort was actually just the traces from the flex ribbon that delaminated and stuck to the PCB.  You can see through the transparent ribbon where the traces came off.  Old and crusty....  Since the traces came off the flex ribbon there was nothing really to solder to even if I wanted to point to point repair it.

So the moral of this story is, seriously don't take apart a "LMBHAT014G18CS".

[Kean]

According to Google (and Dublin Zoo):

On average, zebras live for approximately 20 years in the wild, and up to 40 years in zoos

It sounds like Zebra contact strips in LCD modules have a similar lifespan.
I've found that cleaning them rarely helps, and lining them back up during reassembly can be super tricky.

[Smokey]

According to Google (and Dublin Zoo):

On average, zebras live for approximately 20 years in the wild, and up to 40 years in zoos

It sounds like Zebra contact strips in LCD modules have a similar lifespan.
I've found that cleaning them rarely helps, and lining them back up during reassembly can be super tricky.

  Just have to wait for some scientist to genetically engineer their relatives back from extinction:
https://en.wikipedia.org/wiki/Przewalski%27s_horse

The thing that's not working in this display is not the zebra strip.  That looks fine.  It's the strange ribbon cable like thing that's being used like a zebra strip.  Why oh why not just two zebra strips?  The world may never know.

[Kean]

The thing that's not working in this display is not the zebra strip.  That looks fine.  It's the strange ribbon cable like thing that's being used like a zebra strip.  Why oh why not just two zebra strips?  The world may never know.

Ah yes, I think I know what you are talking about now.  I recall seeing those thin flex ribbons in some LCD modules and cheap calculators.

Buy a new (old stock) module and hope it works...

[Smokey]

I need an actual camera for my microscope.. Sorry for the crappy picture..

You can see the real zebra strip on the top (that's fine), and the crappy delaminated ribbon cable on the right.  The dark lines are actually the rubber showing through where traces used to be.