Need help with grapic eq / spectrum analyzer schematic

Discussion in 'The Projects Forum' started by sandiegoman, Sep 9, 2013.

  1. sandiegoman

    Thread Starter New Member

    Sep 9, 2013
    I have a great graphic eq / spectrum analyzer that I am trying to reduce to a 5 x 5 pattern and putting the LEDs on 3' leads.

    So I need to remove 3 bands, and 1 led from each column. I don't have a very good schematic, I could not find one online, but one did come with the kit I ordered off of Ebay.

    Here are scans of the schematic and parts list.

    I would like to change all the 3mm LEDs to 8mm Straw Hat Wide Angle White LED - Ultra Bright LEDs using 100-120ma and 3.2 - 3.6v.

    I can't believe it, but they actually light up dimly when I swapped 1 row of them out, I would just like for them to have the max brightness.

    I think what might actually be driving the LEDs is the CD4028BF. That seems to have plenty of power, but I am not 100% sure that is the role of that IC. It looks like the lm3915 is switching the negative on and off and the cd4028BF is providing the + voltage. There is a 10k resistor between each of the pins and a bc337 transistor:

    Collector-Emitter Volt (Vceo): 45V
    Collector Current (Ic): 0.8A
    hfe: 100-250 @ 100mA
    Power Dissipation (Ptot): 625mW
    Current-Gain-Bandwidth (ftotal): 210MHz
    Type: NPN

    which then runs to the LED columns.

    I am not sure if that will help. It seems to me the problem is with the transistor. I ran a jumper on the 10k resistor that was between the transistor and the LED columns and that actually dropped the brightness so I didn't think that was the problem.

    Any help would be greatly appreciated! Thanks!

  2. sandiegoman

    Thread Starter New Member

    Sep 9, 2013
    You can disregard this post. Seems to be a sink issue with the LM3915, so I am using a different board for now. If you want to check out my progress, you can see it at