7 Segment display issue - Page 1
Forum section: electronics / general

author: slybunda
author_rank: Regular Contributor
timestamp: February 01, 2024, 09:22:09 pm
content: Hi all, this is the 2nd car charger that has had some segments fail to turn on now. not sure if its just bad quality display or something else in them that causes this to happen.iv attached a pic of the display with some segments not lighting up. is this fixable as in does it need a new display or some other fix?thanks

author: EPAIII
author_rank: Super Contributor
timestamp: February 02, 2024, 12:55:27 am
content: Repair? Here's what you are up against.First, what I/we are up against in answering. You have provided no information beyond the close-up photo of the bad display. Brand name would be nice to know. The model number too. A photo of the entire device also. And what does it cost? Well, since this is the second failure of this model, what about the cost of a DIFFERENT make and model that you can buy? I ask that because there is a very good chance that repairs would be more expensive than just replacing it with a new, and hopefully better one.OK, for repairs:A schematic would be very helpful. This means that the OEM must supply that. I would bet they do not.Are PARTS available? The parts are very likely to be either proprietary or only available in the CoO, probably China.The tone of your post seems to be, what is the likely cause of this problem. This is a good question for someone who HAS repaired a large number of that MAKE and MODEL. I can say this because I have been that person for certain pieces of equipment. And I can also say that what breaks on one device may not be what breaks on another, no matter how similar they may be. I doubt that such a person exists, in the entire world and including in the factory that made your charger. Such devices are not normally repaired.So, getting such an "educated guess" on this particular device is highly unlikely. What I can say about bad displays is the most common reason for them is the connections between the display and the PCB which is driving it. Often the display is not mounted on that PCB so some kind of cable or other connections is needed. And one type of connection that I have seen fail is a strip of alternating conductive and insulating, rubber layers that is sandwiched between the two parts which have matching pads on them. This often occurs when a liquid is spilled on the device and it makes it's way around the display to that connection sandwich. If, upon disassembly you find such a connection sandwich, then careful cleaning with 91% alcohol may fix the problem. Do be careful to not allow the alcohol to flow everywhere as that could cause some additional problems. Cotton swabs dipped in the alcohol would be a good way to use it.If another method of connection is used, then some pressure on the connectors or wiggling of the wires can help diagnose a problem. Of course this must be done while the device is operating so if it uses mains power great care must be taken. And if you feel at all uncomfortable with that, then do not attempt it. You can try just re-seating the connectors with the power plug disconnected.Beyond that there is very little I can offer without more information.

author: berke
author_rank: Frequent Contributor
timestamp: February 02, 2024, 09:04:46 pm
content: Quote from: EPAIII on February 02, 2024, 12:55:27 amProbably a good guess. If you misalign those two parts some segments can get disconnected (appears off), other segments could get a double connection and appear brighter than other segments.

author: tooki
author_rank: Super Contributor
timestamp: February 04, 2024, 12:08:38 pm
content: Quote from: EPAIII on February 02, 2024, 12:55:27 amWhat a strange rant to go on, especially the “tone” comment.I would have left it at “you need to provide a lot more information and context, please.”Quote from: EPAIII on February 02, 2024, 12:55:27 amThat is clearly an LED display. I have never even heard of an LED display using an elastomeric zebra strip, never mind seen it in the wild.

author: tooki
author_rank: Super Contributor
timestamp: February 04, 2024, 12:10:20 pm
content: Quote from: berke on February 02, 2024, 09:04:46 pmAside from the fact that I think it’s extraordinarily unlikely that an LED display would use a zebra strip, every LCD I’ve ever seen with a zebra strip has some sort of bracket to hold the LCD in place, in correct alignment with the PCB. That’s kind of a basic requirement for designing such a display.

author: m k
author_rank: Super Contributor
timestamp: February 04, 2024, 01:56:45 pm
content: My guess is a bad display.Reasoning is that '8' is ok and parallel connection need many pins.Fast blinking is also a very old thing.It can still be a connection problem, but inside of a display part.

author: slybunda
author_rank: Regular Contributor
timestamp: February 04, 2024, 04:01:44 pm
content: It's a generic cheapo unit from AliExpress, the first one that had the display issue and was a plastic unit. New one i got is an aluminium housing and thats gone iffy too.I will probably take it apart and get some photos up.