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New fangled LED display

hafcanadian

Our Ninja CE200 coffeemaker's control module display began acting like its LEDs weren't making solid contacts.  While some came on, others didn't, so I couldn't be sure of what I was setting when adjusting time parameters on the clock. The usual culprit for such behavior is the display contact interface, with a gentle alcohol scrub of the contacts and "zebra" strip being the commonly advised resolution.  

With some difficulty and delay, I finally got the control pad module out of the bottom of the machine so I could get at the circuit boards and display.  Much to my chagrin, the display is not what I've encountered before, nor are there "fixit" videos found on YouTube for this format.  The only comment on iFixit forum was that there was a problem on the board.  Well, yeah... the display connects to the board.  I guess they were thinking the LED assembly itself isn't the issue.  

But it's a different sort of display and doesn't use a zebra strip or wire loom.  It appears to have two rows of six straight wires, 12 altogether, that are soldered directly through the board.  There is a black plastic shell protecting the long wires between the display and the board, with four feet glued or heat-melted to the board.  I can't get at the structure under the white display face to see how its assembled, with hope to find a cleanable short zebra (or two), because I can't tell how it goes together.  I don't want to start prying on something and risk damage.

Does anyone recognize this sort of display assembly and have suggestions on how to rectify the faulty LED power-up?

Display with unit plugged into power:

image

Display with no power:

image

image

image

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  • 0


    Hi,

    That's an LED display (information on it is here: http://sunnyled.net.cn/shows/103/12.html  ) known more precisely as a 7-segment Common Cathode Display and they very rarely get damaged so it's much more likely to be an issue elsewhere, such as a broken solder joint. They don't use zebra strips, they are more common on LCD, not LED displays. Personally I would not remove the LED display yet.

    However, by visually looking at the display issue, you may be able to make a good guess what the issue is.
    Is the display intermittent, or does the display consistently show the same issue? Does the issue affect all four digit positions, or just one or more particular digits?

    The important board views are all out of focus; it would be good to see a detailed, well focussed image of both sides of the boards.

    It is likely that a solder joint may need re-melting. It is also possible there is a driver transistor or chip fault, but a good description of the fault (whether it's intermittent, or consistently one digit that is faulty) will help narrow down further.

  • 0 in reply to shabaz

    Hopefully these images will be of some help:

    (Click on each to enlarge)

    both boards, components side

    image

    both boards, track side

    image

    small board, components side

    image

    small board, track side

    Do ZD1 and 
    ZD2 look okay to you?  They and some other spots look "burned" or melted maybe, when you zoom in?

    The angle and lighting of the photo are deceiving;  in person all looks bright and clean, except for that slight

    wrinkling of the black component surfaces

    image

    large board, components/switches/LED side

    image

    large board, track/solder point side, LED end

    image

    large board, track side, LED end;   limit of camera macro focus

    image

    large board, track side, opposite end from LED

    image

  • 0 in reply to hafcanadian

    It's hard to tell, but you can test the Zener diodes like any other diode, using a multimeter, probably in-circuit i.e. without desoldering, to see if it conducts in one direction. 

    There aren't many components so if you've examined the surface mount parts especially near the switches etc in case they have cracked with too much pressure on the buttons, you could re-melt the solder (and apply a bit of flux or solder) to some/most of the joints. This could also apply to other parts of the board since it can be easily flexed by accident when installing/removing from the enclosure.

    Otherwise, if some segments are permanently unlit, you may need to probe with (say) an LED and resistor, to see if you can get it to light from the microcontroller output or not, and if it does light, then trace the paths and see what's the cause.

Reply
  • 0 in reply to hafcanadian

    It's hard to tell, but you can test the Zener diodes like any other diode, using a multimeter, probably in-circuit i.e. without desoldering, to see if it conducts in one direction. 

    There aren't many components so if you've examined the surface mount parts especially near the switches etc in case they have cracked with too much pressure on the buttons, you could re-melt the solder (and apply a bit of flux or solder) to some/most of the joints. This could also apply to other parts of the board since it can be easily flexed by accident when installing/removing from the enclosure.

    Otherwise, if some segments are permanently unlit, you may need to probe with (say) an LED and resistor, to see if you can get it to light from the microcontroller output or not, and if it does light, then trace the paths and see what's the cause.

Children
  • 0 in reply to shabaz

    My Fluke 365 doesn't have a dedicated diode option, but my old craftsman does.  Not certain about testing in-circuit, but the results for the 3 Z diodes were:

    ZD1:  0.65 one way and 1.17 the other;

    ZD2:  0.65 one way and 1.17 the other;

    ZD3:  0.67 one way and the other way it slides quickly up from about 1.9 to 3.0 and flashes.

    The LCR Research tweezers I foolishly bought a couple of years ago have a diode setting, but they are way over my head to be trying to use.  I think one issue is they put a resin coating of some sort over the board surfaces, and it's difficult to get meter tips through it to a clean contact, even with the pointy LCR tips.  When I try using that I get the diode symbol with a line through it and "damage" for a reading in both directions on all three Z diodes.  The other regular diodes on that small board return readings in one direction and "open" in the other, so I assume they are okay.

    The wife got fed up with the disassembled coffeemaker on her dining table, and finally plopped it on my garage workbench where it's languished for a couple of weeks, in my way.  So I reckon I must resolve to my lack of electronics skills on this one, put it back together (if I can remember what goes where after many weeks), and get along with a relatively unreadable screen.  I may call Ninja techs' phone number that I obtained and see what they say.  If they're like Keurig that sent free new parts for our 5 year-old K-cup coffeemaker, Ninja  might be amenable and send me new boards... yeah, right.