Hello everyone! I am trying to fix a faulty 7-segment 2 digit LED display. Several segments do not light up on the left digit. The only marking I see on it is HGA4023HB-1. It’s 8 pin, and only along the bottom. Any ideas for a replacement part?

 

Welcome to AAC!

From the HGA prefix, I'd guess that it's common anode. Count the number of pins, see if you can verify whether it's common anode or cathode. There might be some parts that are designed to be multiplexed (i.e. share segment pins, but have separate digit cathodes/anodes), but most will be separate.

The size should be standard.


You might be able to check polarity in-circuit with a diode checker. If not, remove it from the board and test.

 

It’s 8 pin, and only along the bottom. Any ideas for a replacement part?

I missed this part. It must be a custom display because it takes at least 9 pins for a multiplexed display like this:

 

Looking at the pin connections to the controller, it looks like a 4x4 multiplex affair with each digit divided into 2 sets of 4 segments. Never seen one like that before and the Google is silent on the part number. Maybe made only for Asian markets or a special with a custom part number.

 

Thank you all for your help. This one is a bit dicey... I might desolder it and hope there is some sort of a schematic underneath, but I doubt it. I guess since it‘s multiplexed, the missing digits can’t be due to a dry solder? But it could be caused by a problem with the MCU? Sorry for the rookie questions, I haven’t done diagnosis since college!

 

I agree with JohninTX on the 4 x 4 multiplexing. (I had not thought of that. I was thinking that one pin was selecting one digit when low and the other when high but looking at the 4 current limiting resistors points to JohninTX's conclusion.) I think it is possible that the fault could be external to the display. If you make a note of which segments do not work you could test the display removed from the unit using a 470 ohm resistors and a power supply with the same voltage as the supply the chip. You would first have to measure the voltage across one of the 470 ohm current limiting resistors so you would know the polarity for testing.

Les.

 

This isn't rocket science. It's a 4023 model [H]igh efficiency [G]asp/[G]reen common [A]node 2-digit 7-segment display. It's pinout will probably match a 4022 or 4024 if you look around, and you can look at other colors. You might also see if a MAN6410 (Fairchild) matches.

Desoldering it and use a diode-tester on your meter- it's easy to see what pins tie to what segments, and polarity whether anode or cathode common.

IMPORTANT: What are the dimensions of the display- that can help you match with an alternative. MAN6410:

 

This isn't rocket science.

But the display in question has only a single row of 8 pins.

 

Hello,

What if the display is a "inteligent" display with a decoder build in?
Then you would have four pins for the value, a pin for the dot and a pin for wich number to display.

Bertus

 

Here is another source for reference. Not much detail but... https://www.aliexpress.com/wholesal...12140647&SearchText=2+digit+7+segment+display

 

Thank you all for your help. I was finally able to desolder the display and check the pinout.

It’s a multiplexed display:
Pin 1 is common cathode for 3 segments (1st digit, abc) with pin 5 anode.
Pin 2 is common cathode for 4 segments (1st digit, defg) with pin 6 anode.
Pin 3 is common cathode for 3 segments (2nd digit, abc) with pin 7 anode.
Pin 4 is common cathode for 4 segments (2nd digit, defg) with pin 5 anode.

From what I’ve found, it’s also called a G/H multiplex. I’ve found one equivalent here (second 8-pin):
http://www.snowdragonledhk.com/new-two-digit-40.htm

Anyone have an idea where I could purchase a replacement part? Because of the layout, I don’t see how I could use a standard display as a replacement, even by rewiring it.

Any help appreciated!
Justin

 

Hah! Called it.
That said, I’ve never seen one like like that. I don’t think you can rewire a standard one, either. You MIGHT be able to re-map the segments using some external logic that decodes the 4 common lines to select a corresponding subset of segments and routes the 4 bit data to them then ORs the pairs of ‘digit’ selects from the controller to the common of the new display. Hmmm..

A multiplexer with that selects between 2 4bit channels might do it. One of the 2 digit original commons would select the group of segments to route the 4bit data to. The two commons would be or’ed to drive the new single digit common. Repeat for the other digit. The details are somehow obvious (h/t Signetics 25120)

or a little microcontroller..
or roll your own little PCB with SMT LEDs and light pipes...