LCD 7 segment display - Replacement - Page 1
Forum section: electronics / repair

author: 2X
author_rank: Frequent Contributor
timestamp: February 25, 2025, 08:16:40 pm
content: Hello,I have the below LCD 7 segment display with four digits. Do you know If I can find a replacement and if yes… where?Also,One from the two displays on the back have a PCB where I can’t understand what it is (I don’t have much experience with LCD displays... specs and brands). Does anyone knows what is this PCB?I found the below that seems similar.. could anyone with more experience on LCDs check it?Manufacturer Part No: LCD-S401C52TRhttps://uk.farnell.com/lumex/lcd-s401c52tr/numeric-lcd-display/dp/1535928

author: edavid
author_rank: Super Contributor
timestamp: February 25, 2025, 08:24:29 pm
content: Quote from: 2X on February 25, 2025, 08:16:40 pmLooks like a backlight.QuoteSeems fine if the pinout and voltage match.

author: 2X
author_rank: Frequent Contributor
timestamp: February 25, 2025, 08:31:58 pm
content: Quote from: edavid on February 25, 2025, 08:24:29 pmI checked the pinout and the working voltage and both are the same.Do you know or can you imagine what I have to connect in order the backlight to open?

author: edavid
author_rank: Super Contributor
timestamp: February 25, 2025, 08:38:04 pm
content: Quote from: 2X on February 25, 2025, 08:31:58 pmIf it's LED, probably 5V, but you might need an external current limiting resistor, so be cautious. Can you look from the side and see if there are surface mount LEDs under the LCD panel?There is a small chance that it's an EL backlight, which would need something like 80VAC.How old is the LCD and where did it come from?

author: 2X
author_rank: Frequent Contributor
timestamp: February 25, 2025, 09:58:03 pm
content: These LCDs are from a control panel of a Fendt 250V 1991 tractor. I dismantled the white panel and seems that have tiny LEDs embedded on this white sheet/PCB… I have never seen something like this. I used 1K and 330 ohm resistor with 5V supply but no light.Also, I tried to measure each of them with a multimeter on diode mode (EEVBlog 121GW) but no one light. The guy who gave me this told me that the tractor when he bought it the LCDs didn’t have light and he gave it to a repair shop and the technician soldered LED from the side in order to have illumination on night.

author: 2X
author_rank: Frequent Contributor
timestamp: February 25, 2025, 10:27:50 pm
content: Quote from: edavid on February 25, 2025, 10:17:00 pmUnfortunately I don't know what voltage supply the LEDs because the cables from the white panel were cut. Do you know if there is any panel like this to buy? Strange thing is when I measured each single LED with multimeter in diode mode no one LED illuminated... maybe something happened and all LEDs burned out (rare phenomenon all LEDs to burn out)... I don't know.Thanks for your time and your replies.

author: quag
author_rank: Newbie
timestamp: February 26, 2025, 11:22:46 pm
content: Quote from: 2X on February 25, 2025, 08:16:40 pmLooks similar to EDC190 LCD to me.It's available from many sellers on AliExpress.

author: 2X
author_rank: Frequent Contributor
timestamp: March 01, 2025, 08:47:45 pm
content: I tried to light some LEDs with the multimeter in diode mode... each LED where illuminated it shown Vf=~2V. Some LEDs I believe are "at the edge of short-circuit" because sometimes the LEDs that I tested with the multimeter flickering and sometimes continuously illuminated. I thought to remove them and solder SMD LEDs 0402 package (I will post photos when I will do it).If anyone knows where I could find a new one panel backlight so thin like mine please tell me.The dimensions of the below doesn't fit in my PCB:EDC190 LCD backlight Blue White Yello Colorhttps://www.aliexpress.com/item/1005004015314165.html?spm=a2g0o.cart.0.0.30d038daqmlyDN&mp=1&pdp_npi=5%40dis%21EUR%21EUR%201.23%21EUR%201.23%21%21%21%21%21%402103956b17408619433633703eef14%2112000029217071661%21ct%21GR%21138459962%21%211%210EDC190 40PIN TN Positive 4 Digits Segment LCD Display Panel 3V Digital Tube Clock Displayhttps://www.aliexpress.com/item/1005003178474441.html?spm=a2g0o.cart.0.0.30d038daqmlyDN&mp=1&pdp_npi=5%40dis%21EUR%21EUR%203.74%21EUR%203.18%21%21%21%21%21%402103956b17408619433633703eef14%2112000024523829174%21ct%21GR%21138459962%21%211%210

author: quag
author_rank: Newbie
timestamp: March 02, 2025, 09:20:53 am
content: Quote from: 2X on March 01, 2025, 08:47:45 pmI don't remember seeing anything like that for sale. Side illuminated, like those bundled with EDC190, are prevalent.There are electroluminescent backlight sheets that may be cut to size, seehttps://www.eevblog.com/forum/repair/el-backlight-replacement/But they require 100VAC or so to work - inverter needed. Not the best solution.

author: 2X
author_rank: Frequent Contributor
timestamp: March 02, 2025, 09:23:51 am
content: Quote from: quag on March 02, 2025, 09:20:53 amThanks for your time and your replies.

author: quag
author_rank: Newbie
timestamp: March 02, 2025, 10:42:49 am
content: Quote from: 2X on March 02, 2025, 09:23:51 amI know how hard search for suitable replacement can be.