Connect with us

REQ: Emerson 19" tv TC1993 no power

Discussion in 'Electronic Repair' started by Jan, Feb 19, 2004.

Scroll to continue with content
  1. Jan

    Jan Guest

    Need info on low voltage regulator str 30130.

    Any advice appreciated.
    TIA
    Jan
     
  2. Sofie

    Sofie Guest

    Jan:
    If it is not putting out regulated B+ @ 130 V DC it is most likely
    faulty..... obviously the other supporting circuitry can cause a B+ faults
    like shorted loads (always look for a bad HOT), bad pre-regulator diodes and
    filter, faulty base drive/reference, open resistors, etc. The STR 30130 is
    usually a fairly reliable unit as long as it is heat sinked well and the
    solder connections aren't cracked or dry.... or there isn't a fault before
    or after the chip.
    Pin 1 Common
    Pin 2 Base
    Pin 3 Input
    Pin 4 Output
    Pin 5 n/c

    Best Regards,
    Daniel Sofie
    Electronics Supply & Repair
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     
  3. Jan

    Jan Guest

    Thank you for your input.

    I am first year EE student and appreciate your efforts.

    I have no voltage out of the regulator.

    There is a relay that is not energizing and I assume that;s because
    there is no high voltage.

    A viscious circle.

    How to continue?

    No schematic .

    Thanks again

    Jan
     
  4. Sofie

    Sofie Guest

    Jan:
    Slow down a little.... there is a lot of successful troubleshooting and
    repairing that can be done without a schematic. Take some time and trace
    the circuitry with your eyes..... checking different components with your
    DMM.
    There is no high voltage because there is no regulated 130 v B+ coming out
    of the chip and there are a lot of reasons that there is no voltage coming
    out of the chip....... is there "raw" B+ at pin 3 ? (~ 150 V) of the
    regulator chip as referenced to pin 1? Did you check for shorted parts and
    components in the circuitry after the chip? (see my previous reply post with
    suggestions) Do you have a replacement chip that you can install?
     
  5. Jan

    Jan Guest

    Thanks for the advice .

    I have been doing some eyeballing with mag glass also and cannot see
    any open traces etc.

    Volt reg chip has 0 volts on pin 3.

    Volt reg chip pin 3 goes to the relay contact through a resistor that
    is not open.

    I also have obtained a capacitor esr tester and I am in the process of
    testing some caps in the power areas.

    Hot appears to test ok out of circuit using meter diode testing bce;
    but I have no reference to compare. base collector 520 ohms and base
    emitter 49 ohms; I believe this is because of diode internal.

    I will be obtaining an HOT and volt reg chip on Monday and will keep
    you informed of my progress.

    Thanks Jan.
     
  6. Sofie

    Sofie Guest

    Jan:
    You might check for a 3 terminal regulator chip.... maybe a 7805 or
    7806.... on the board that supplies standby voltage to the syscom chip....
    sometimes near and around the VCR circuitry.... if there is no standby B+
    going to the syscom chip then it won't energize the relay when the power
    button is pressed.
     
  7. Jan,
    One end of the relay coil connects to the standby power supply, the
    other end to the relay switching transistor. The standby supply powers
    the microprocessor, relay switching transistor and relay coil. When
    the power button is pressed the microprocessor turns on the relay
    switching transistor supplying 5 volts through a resistor to the base.
    The relay closes and provides input to the STR30130. Look to see is
    the base of the relay switching transistor getting its forward bias
    when the power button is pressed.
    Gordon Gaskell AAS
    Home Electronics of Havre de Grace, Maryland
     
  8. Jan

    Jan Guest

    Thanks for the info Gordon.

    I checked the voltage at the base of the relay switch transistor.

    This was measured as .5 volts.

    I also replaced the HOT and the volt regulator on spec.

    I believe the relay is not picking up to supply voltage to regulator.

    Cannot trace where the relay is fed from.

    Thanks

    Jan
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-