Analytical Scale dead display - Page 1
Forum section: electronics / repair

author: Rutherford
author_rank: Newbie
timestamp: November 01, 2024, 11:40:01 pm
content: Hello,I have an analytical scale but this morning the LCD was doing weird things (displaying the top and bottom but not the middle segment), and just not responding to input. After I turned it off and on again, the display stopped working at all.Does this look like a CCFL failure mode? I'm tempted to change it out, but very skeptical it will do anything and worried it might be the LCD itself. I think I might be able to use the rs232 port as I see there's a bit stream there. Anyway, I'll end my rambling with some photos, and will update with any findings.I might do a nice photoshoot because the load cell is something to behold (everything is made in Switzerland), truly marveled with the engineering behind it. It might not work, but it's well-made no doubt. Any tips or comments are very welcome.EDITED for PI

author: kmm
author_rank: Regular Contributor
timestamp: November 04, 2024, 07:18:10 am
content: Losing a region of the display sounds like a whole row array driver chip is out rather than a backlight issue. I'd expect backlight would be intermittent, nothing, or a dim gradient starting from the edge where the CCFL is, and a bad "zebra strip" interconnect usually leaves one or more dead rows of pixels rather than a whole region. Shining a bright light on a LCD panel will usually at least reveal if there's an image even if the backlight is out, might need to look from multiple grazing angles.I'm not finding a datasheet for this module but plugging in LMBFAT410G2CD turns up a couple vendors that at least have them up supposedly for sale, so that might be an option if the LCD actually died. I can only see part numbers on the actual row/column driver chips not the controller (likely the rectangular flatpack IC nearest the BS62LV256 SRAM), but it looks like a pretty typical sort of 20-something pin interface for a graphic LCD module so there might be other ones that are at least adaptable. From what I gather the geometry is 320x240 mono.Worth checking the system power rails for sanity and hitting all the contacts with deoxit just to rule that stuff out, especially since you mentioned it wasn't responding to input (keypad doesn't seem to be integral to the LCD module from the look of it, suspect keys are just scanned by the 80C32). Just re-seating all the connectors may help, possible it got jostled during shipment and something was intermittent.Looks like this balance uses a power brick of some sort, that might be something to check to make sure you're not giving it something like half (or double...) the line voltage it's expecting, and also just checking that it's producing the expected output voltage(s). Manual I found for what looks like this overall model class says it wants 12V AC or DC, so it sounds possible the power brick may just contain a transformer in at least some regions. With used gear they also may have provided a brick that isn't original and may be undervolting it close enough to make it work but not close enough to be stable, or overvolting it but not enough to instantly kill it.

author: Rutherford
author_rank: Newbie
timestamp: November 04, 2024, 09:42:12 pm
content: Hello, thank you for your reply. I will try your recommendations. From what I can gather, this is in fact a 5.1" 240x128 display, some of the documentation I found online for this model stated this.Drivers of interest:LC7931D dot-matrix LCD driver.LC9400D dot-matrix LCD driver.LC7942ND dot-matrix LCD driver.LT1183 driver for the CCFL and the LCD contrast.I've found some interesting displays that might be compatible, I'm inclined to try the SP14N003, but then again I might be wrong.https://www.aliexpress.com/item/32916206837.html

author: graphtronics
author_rank: Contributor
timestamp: November 19, 2024, 03:32:37 am
content: HiIf you were to declare the brand, model and serial number, some help might be available.