Author Topic: LCD got frostbites?  (Read 7115 times)

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Offline max666

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LCD got frostbites?
« on: March 28, 2015, 09:40:56 pm »
I want to fix this LCD for a friend of mine, but I'm also rather puzzled on what happened to it. (It's the remote of a telescope autotracking)
My first guess was damage due to freezing. He said temperature couldn't have been lower than -18 °C tops and no longer than an hour.
Have you guys ever seen anything like this?

The broken off corner seems to me to have been already there since manufacturing (bad case design). Also there probably wasn't any notable pressure or percussive stress on the display, because the case and protective plastic glass are scratch free.

Now to the problem at hand, where to get it. Do you guys know where I can find something that matches:
128 x 64 (or very close, I've given up counting after the 20th failed attempt  :scared:)
Module Size - 69,2 mm x 49,9 mm x 2,64 mm (5 mm thick with the backlight)
Viewing Area - 60 mm x 33 mm
Transflective / Transmissive
30 pin flatflex (0,5 mm pitch)

I've taken a look around RS and Mouser and only on Mouser I've found one that I think comes fairly close:

Newhaven Display NHD-C12865BR-FSW-GBW

Pin configuration looks to be right. Should I go with this one? Suggestions? (Never baught anything from Mouser)
 

Online Ian.M

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Re: LCD got frostbites?
« Reply #1 on: March 28, 2015, 10:16:00 pm »
The damage looks typical of excessive pressure on the face of the display. 

It doesn't have enough conductors in the flat-flex cable to be a passive display so it must have an integrated chip-on-glass or chip-on-flex display driver.   Basically you need either an exact replacement or you need to find a datasheet for the damaged display so you can try to find one with a compatible display driver.
 

Offline wraper

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Re: LCD got frostbites?
« Reply #2 on: March 28, 2015, 10:27:46 pm »
It likely to have the same/compatible controller (st7565), however you need display without backlight. If you buy one with backlight with intention to remove it later, buy green/grey positive lcd. It will work without backlight too. Don't buy blue LCDs, you won't see almost anything on them without backlight. Isn't there any marking on the LCD?
« Last Edit: March 28, 2015, 10:39:33 pm by wraper »
 

Offline wraper

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Re: LCD got frostbites?
« Reply #3 on: March 28, 2015, 10:45:20 pm »
If there is no any marking, it is worth at least to check if the power pins are the same. Check where traces on the pcb go and compare them with the datasheet of replacement candidate .
 

Offline max666

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Re: LCD got frostbites?
« Reply #4 on: March 28, 2015, 11:46:41 pm »
hmm ... ok, so you guys think it was pressure on the face of the glass. It certainly is a possibility, I've just ruled it out because of the pristine look of the plastic window, but maybe that was premature. Most LCD's are also rated to -20 °C, so I guess damaging by cold is rather unlikely.

The only marking on the LCD is LCD174A FP-1 on the flatflex, which got me nowhere.

I've checked VDD and VSS, they check out. The data lines look good and also the five capacitors to the power supply are where they supposed to be. I didn't check the rest of the miscellaneous pins, but to me that looked suspiciously good.

I can't figure out whether the Mouser Newhaven Display NHD-C12865BR-FSW-GBW is one of these (don't know what they are called):

or simply one of the standard ones, but with blue instead of black font colour:

Since it will be mostly used when it's dark, I'm not sure how much it matters. Also the Mouser one is only 0,9 mm higher, so I could probably fit that in with the original backlight.
 

Online VK5RC

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Re: LCD got frostbites?
« Reply #5 on: March 28, 2015, 11:51:13 pm »
As a comment, I would tend to replace what was there regarding backlit LCD or not, for night time work dark adaptation of eyes can be very important.
Whoah! Watch where that landed we might need it later.
 

Offline wraper

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Re: LCD got frostbites?
« Reply #6 on: March 29, 2015, 12:33:19 am »
I can't figure out whether the Mouser Newhaven Display NHD-C12865BR-FSW-GBW is one of these (don't know what they are called):

or simply one of the standard ones, but with blue instead of black font colour:

Since it will be mostly used when it's dark, I'm not sure how much it matters. Also the Mouser one is only 0,9 mm higher, so I could probably fit that in with the original backlight.
These displays certainly won't work. They have completely different controller.
 

Offline wraper

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Re: LCD got frostbites?
« Reply #7 on: March 29, 2015, 12:41:03 am »
Mouser display is:
Transflective   
Fluid Type:   STN Positive

So will work without backlight, however it is out of stock.
 

Offline max666

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Re: LCD got frostbites?
« Reply #8 on: March 29, 2015, 12:46:29 am »
Oh right, the stock!
Quote
Factory Lead Time:    16 Weeks
Damn it!
And since we're at it
Quote
Minimum: 64
  :palm:

Like I said, I'm a n00b to Mouser ...
 

Offline wraper

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Re: LCD got frostbites?
« Reply #9 on: March 29, 2015, 12:55:27 am »
Loook for something else with st7565 controller an 30 pins.
 

Offline wraper

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Re: LCD got frostbites?
« Reply #10 on: March 29, 2015, 12:59:21 am »
BTW, unless you going to spend significant money on parts, shipping cost from mouser will be a killer.
 

Offline mikron

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Re: LCD got frostbites?
« Reply #11 on: March 29, 2015, 07:02:25 am »
Three months ago I bought a meter on Ebay and received it with some damages due to bad packaging. The LCD had a number of black spots similar to yours, apart from that it was still working.
Fortunately it turned out that these spots were caused by small amounts of water (condensation?) between the glas and the polarizer layer of the display. They disappeared without any effort on my part - but it took months.
 

Offline bktemp

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Re: LCD got frostbites?
« Reply #12 on: March 29, 2015, 09:26:15 am »
I have seen similar damages several times. If you apply pressure on a small point you get those organic looking pattern. It is impossible to repair, but the lcd is still usable.
As far as I know the orientation of the liquid crystals gets messed up. Those are aligned during manufacturing. When applying an electric field the orientation changes but goes back after the voltage is removed.
Applying a lot of pressure the orientation can change without an electric field. Maybe this is also possible due to extreme temperatures. Since the molecules are large chains it effects surrounding molecules, generating those patterns.
 

Offline max666

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Re: LCD got frostbites?
« Reply #13 on: March 29, 2015, 10:56:14 am »
Loook for something else with st7565 controller an 30 pins.
wraper, you're a genius!
If you know the controller designation, then searching for that makes finding appropriate displays a breeze.

http://www.buydisplay.com/default/2-6-inch-spi-serial-graphic-lcd-128x64-nt7538-controller-black-on-white  :-+
 

Online Ian.M

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Re: LCD got frostbites?
« Reply #14 on: March 29, 2015, 11:51:21 am »
I'd like to know how wraper knows your display has a ST7565 controller.

 

Offline wraper

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Re: LCD got frostbites?
« Reply #15 on: March 29, 2015, 11:55:01 am »
I'd like to know how wraper knows your display has a ST7565 controller.
I don't know, just seem to be likely. Moreover OP checked pinout and power pins seem to be the same.
 

Offline max666

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Re: LCD got frostbites?
« Reply #16 on: March 29, 2015, 12:27:05 pm »
I'm not familiar with COG display controllers, so I don't know how many different 128 x 64 controllers there are.
But a tedious parametric search on RS and Mouser only spit out one possible candidate based on size, dimensions, resolution and that one has a 30 pin flatflex and the pinout appears to be the same and that one is a ST7565R. Additionally wraper said a ST7565 controller seems likely, so that's good enough for me.

For US$6.71 plus shipping, I'm going to cut this short and simply try it.
 

Online Ian.M

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Re: LCD got frostbites?
« Reply #17 on: March 29, 2015, 12:31:18 pm »
I agree its a worthwhile gamble.
 

Offline bktemp

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Re: LCD got frostbites?
« Reply #18 on: March 29, 2015, 05:56:06 pm »
There are a lot of lcd controllers capable of 128x64, but most of them have a similar instruction set and are software compatible.
Since the old display still works, you can measure the voltages on C8-C12. If it is positive, a display with ST7565R might work. If it is negative, you need a display with a different controller (ST7565S or ST7565V uses negative voltage).
 

Offline max666

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Re: LCD got frostbites?
« Reply #19 on: March 29, 2015, 09:09:10 pm »
Thanks bktemp.

The pcb follows this circuit:


and pins V1-V5 (respectively C8-C12) do have positive voltages relative to ground Vss.
 

Offline miguelvp

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Re: LCD got frostbites?
« Reply #20 on: March 30, 2015, 04:19:25 am »
I have a DMM that I left outside while it was sub 0 (Fahrenheit) and had the same problems, but months later it's back to normal, didn't even noticed when it came back.

So probably is a condensation issue that fixes itself.
 


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