New Here - Trying to ID component

Discussion in 'General Electronics Chat' started by superdart, Jun 23, 2009.

  1. superdart

    Thread Starter New Member

    Jun 23, 2009
    I am working to repair a power supply board for a Pioneer DVL-700 Laser Disc player. No formal board level education, so please bear with me.

    I located a faulty diode, which was located at D252 on the attached image. I have desoldered it, and the only marking on it is "C30". It comes up only as a Zener Diode whenever I try to do searches on it.

    Can someone help me out here? It is physically identical to the Diode located at D255.

    This diode was burned up, as well as a resistor that was causing a dead short.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    It is a standard diode - a zener has a different symbol. The fun part is guessing about the current and voltage. It looks like you have room to stand a component up vertically. You might try something like a 1N4004. That is 400 volts and one amp. It's only good for a 60 Hz rectifier, though.

    If that is rectifying a switch mode supply, then a Schottkey diode with fast recovery will be needed. That will be low voltage, so a 60 volt diode good for an amp should be plenty. That is pure guesswork, though.
  3. bertus


    Apr 5, 2008

    When you can get hold of the schematic, you can look it up in the schematic.
    The symbol used is a standard diode symbol as beenthere said.

  4. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    Can you see on the back how the components are connected? You may be able to see how the component fits into the circuit if you can recreate part of the schematic.
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Same goes for me..if the diode is burnt then schematic tracing is the way if no schematic is there.

  6. superdart

    Thread Starter New Member

    Jun 23, 2009
    Thanks for the fast response. From what I have found online the schematics are all but impossible to get for this player.

    I can easily see the paths on the back of the board however. I'll post more pics when I get home.
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Contact Pioneer they have good tech support, and can probably fax you a copy of that page from the repair manual.

    C30 as a zener is 30v, I really doubt it was a 30v zener in that package and that part of the PCB. Does that laserdisc player even have a 30v or 24v supply?
  8. superdart

    Thread Starter New Member

    Jun 23, 2009
    More pics of the board (front and back).

    AFAIK there is nothing in the 24-30V output range on the power supply.

    I can try to get a hold of Pioneer. I also need to locate a replacement Diode P/N UKV46N, it is shorted and was causing the on board 3A 125V fuse to pop as soon as I applied power to the board.
    Last edited: Jun 23, 2009
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    You dont show where that large diode came from? That's NOT good.

    Re the other diode I think you got problems. Transformer T251 is a SMPS that generates a number of supply rails. Its oscillator is Q252 driving the power transistor Q251. There is an obvious negative voltage rail see D254 driving C253, which supplies neg voltage to the anode of the dead diode D252 which I am starting to think WAS a 30v zener. It was definitely a zener (as is D255) as theres no need to generate a neg rail and connect that to 2 anodes of signal diodes.

    I would suspect Q252 of being blown and replace it, and test Q251 or maybe just replace it. If that is shorted the strain may have taken out your big PSU diode. Check the fusible resistor R252 and check/replace the yellow fuses, especially F210 which powers this whole SMPS supply.

    The main purpose of this whole SMPS seems to be generating 2 AC voltages which it sends to pins 3 and 4 of conn 204 and the negative rail also sent to pin 5 of con204. I'm guessing this is to drive a VFD display on the front panel? That sort of stuff is nice to know and you could have described the fault, or at least what the connectors were attached to...