LCD got frostbites? - Page 1
Forum section: electronics / repair

author: max666
author_rank: Frequent Contributor
timestamp: March 28, 2015, 09:40:56 pm
content: 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)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 mmTransflective / Transmissive30 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-GBWPin configuration looks to be right. Should I go with this one? Suggestions? (Never baught anything from Mouser)

author: Ian.M
author_rank: Super Contributor
timestamp: March 28, 2015, 10:16:00 pm
content: 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.

author: wraper
author_rank: Unknown
timestamp: March 28, 2015, 10:27:46 pm
content: 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?

author: wraper
author_rank: Unknown
timestamp: March 28, 2015, 10:45:20 pm
content: 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 .

author: max666
author_rank: Frequent Contributor
timestamp: March 28, 2015, 11:46:41 pm
content: 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 isLCD174A FP-1on 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 MouserNewhaven Display NHD-C12865BR-FSW-GBWis 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.

author: VK5RC
author_rank: Unknown
timestamp: March 28, 2015, 11:51:13 pm
content: 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.

author: wraper
author_rank: Unknown
timestamp: March 29, 2015, 12:33:19 am
content: Quote from: max666 on March 28, 2015, 11:46:41 pmThese displays certainly won't work. They have completely different controller.

author: wraper
author_rank: Unknown
timestamp: March 29, 2015, 12:41:03 am
content: Mouser display is:TransflectiveFluid Type: STN PositiveSo will work without backlight, however it is out of stock.

author: max666
author_rank: Frequent Contributor
timestamp: March 29, 2015, 12:46:29 am
content: Oh right, the stock!QuoteDamn it!And since we're at itQuoteLike I said, I'm a n00b to Mouser ...

author: wraper
author_rank: Unknown
timestamp: March 29, 2015, 12:55:27 am
content: Loook for something else with st7565 controller an 30 pins.

author: wraper
author_rank: Unknown
timestamp: March 29, 2015, 12:59:21 am
content: BTW, unless you going to spend significant money on parts, shipping cost from mouser will be a killer.

author: mikron
author_rank: Contributor
timestamp: March 29, 2015, 07:02:25 am
content: 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.

author: bktemp
author_rank: Super Contributor
timestamp: March 29, 2015, 09:26:15 am
content: 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.

author: max666
author_rank: Frequent Contributor
timestamp: March 29, 2015, 10:56:14 am
content: Quote from: wraper on March 29, 2015, 12:55:27 amwraper, 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

author: Ian.M
author_rank: Super Contributor
timestamp: March 29, 2015, 11:51:21 am
content: I'd like to know how wraper knows your display has a ST7565 controller.

author: wraper
author_rank: Unknown
timestamp: March 29, 2015, 11:55:01 am
content: Quote from: Ian.M on March 29, 2015, 11:51:21 amI don't know, just seem to be likely. Moreover OP checked pinout and power pins seem to be the same.

author: max666
author_rank: Frequent Contributor
timestamp: March 29, 2015, 12:27:05 pm
content: 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.

author: Ian.M
author_rank: Super Contributor
timestamp: March 29, 2015, 12:31:18 pm
content: I agree its a worthwhile gamble.

author: bktemp
author_rank: Super Contributor
timestamp: March 29, 2015, 05:56:06 pm
content: 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).

author: max666
author_rank: Frequent Contributor
timestamp: March 29, 2015, 09:09:10 pm
content: Thanks bktemp.The pcb follows this circuit:and pins V1-V5 (respectively C8-C12) do have positive voltages relative to ground Vss.

author: miguelvp
author_rank: Super Contributor
timestamp: March 30, 2015, 04:19:25 am
content: 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.