Projector TV problem

Discussion in 'General Electronics Chat' started by lowly5, Mar 28, 2008.

  1. lowly5

    Thread Starter New Member

    Jan 17, 2008
    Im working on a 42" projection TV, the brand says StudioSeries and unfortunately I have no schematic. When I press the power button a red led turns on and off then after a few times if just goes off. The voltage on the AC to DC converter is about 328vDC and it stays constant when the led goes off. There is no voltage reading at the fuse when the led is blinking or when it goes off, what sould I check next? I would think the next step is to check for a shorted capacitor or check the regulator again what do you advice? Im new to the field and I am trying to get experience so any advice is greatly appreciated thank you all.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    It's irritating, but schematics are generally not provided with electronic equipment of any sort these days.

    You could read up on SMPS operation to see what might be going on. Be extremely careful, though. The input is not isolated from the line, so that high DC voltage is also very lethal. The charge on the input capacitor is also lethal after the line cord is disconnected, so you have to ask yourself if the risk is worth it.
  3. SgtWookie


    Jul 17, 2007
    I've used Sams PHOTOFACT schematics for a number of years. Fortunately for you, they are available online now as E:facts for less than the printed versions. They're more than just schematics; along with component specifications they also show voltage levels and waveforms at various points in the circuits.

    Here is their website:

    They cover a lot of different makes and models, but not absolutely everything. Sometimes it takes a while for them to publish a PHOTOFACT on a new piece of equipment.

    About a year ago, I downloaded an E:fact (cost $10) for one of my TV's that had blown a HV cap, and along with it a Zener diode and a resistor. There wasn't enough left of the diode or resistor to tell what they were. Put in the new parts, checked voltages, put it back together and it's still working fine a year later.

    (I have no other relationship with Sam's Technical Publishing other than being an occasional consumer of their products)
  4. lowly5

    Thread Starter New Member

    Jan 17, 2008
    I just wanted to thank you again for reading my question I really appreciate your help and advice. Thank you