Variance of Zener Diodes?

Discussion in 'General Electronics Chat' started by hihoslva, May 5, 2008.

  1. hihoslva

    Thread Starter New Member

    May 5, 2008
    Hi all - glad to find this resource.

    I know little about electronics but I'm a tinkerer. So when my LCD TV cut out on me I made it my mission to fix it myself.

    It is a power supply issue, requiring the replacement of 3 blown capacitors and a shorted zener diode. However, I cannot [locally] find the correct diode value of 27v/1w.

    Since they are cheap, I purchased both a 24v/1w and a 30v/1w zener. Through research, I've learned that I can safely change (raise) the voltage value of the capacitors I need to replace (from 16v to 25v) and may even wind up with a more reliable device when done.

    Can the same be done with the zener diode? And if there is an allowable variance here, which diode should I use; the 24v or 30v?

    Thanks for any and all advice!

  2. SgtWookie


    Jul 17, 2007
    I suggest that you replace it with a 1N4750A, 27V 1W Zener. carries them for as little as $0.05 each.
    Make sure you order the right mounting technology. View the datasheets.

    While there are tolerances in electronics, some voltages need to be pretty close depending upon the circuit design. You're considering replacing a part that is a voltage regulator with other parts that have a voltage more than 10% different than the original part, which is not good.

    Considering what it might cost you to replace your LCD TV, the part with the correct value is an amazing bargain indeed, even if you pay extra for overnight shipping.

    But since you're a tinkerer, if there's room, you might consider using a 12V and a 15V Zener in series, which also works out to 27V. This will decrease their individual power dissipation by roughly half. Besides, you can order several of each, and have some useful values for building your own power supplies for projects.
    1N4742A 12V
    1N4744A 15V

    It is perfectly OK to use capacitors that have voltage ratings higher than originally specified, as long as they will fit in the space. It's the capacitance rating and construction of the capacitor that is important.
    Last edited: May 5, 2008
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    I might also suggest that the replacement capacitors have some headroom. Running a 25 volt capacitor on a 27 volt line is not good practice. Go up to 35 volts at least.
  4. hihoslva

    Thread Starter New Member

    May 5, 2008
    Thanks so much for the great, fast replies. In all likelihood I'll be placing an order from Mouser today!