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Sharp Microwave powers down after 40 seconds, need assistance

Discussion in 'Electronic Repair' started by electroninja, Jan 7, 2005.

  1. electroninja

    electroninja Guest

    Test results:

    Tested the zener diode during operation cycle:

    Voltage at inital unit plug-in to AC line was 2.24 volts DC
    Voltage during run runcycle and at shutdown was 2.23 volt
    Conclusion: Would not appear diode was fault solution

    Comments?
     
  2. electroninja

    electroninja Guest

    Test results:

    Tested the zener diode during operation cycle:

    Voltage at inital unit plug-in to AC line was 2.24 volts DC
    Voltage during run runcycle and at shutdown was 2.23 volt
    Conclusion: Would not appear diode was fault solution

    Comments?
     
  3. NSM

    NSM Guest

    | Sam
    |
    | I'm ready to test the diode voltage--DC voltage setting correct?

    Yes.

    N
     
  4. NSM

    NSM Guest

    | Test results:
    |
    | Tested the zener diode during operation cycle:
    |
    | Voltage at inital unit plug-in to AC line was 2.24 volts DC
    | Voltage during run runcycle and at shutdown was 2.23 volt
    | Conclusion: Would not appear diode was fault solution

    That's VERY low for a zener. Not impossible, but I wonder if it is a zener?
    Also, you can't deduce from your test that the zener is good or bad. At this
    point I would try to test it out of circuit.

    N
     
  5. electroninja

    electroninja Guest

    NSM--Ich versuche Ihre Antwort.
     
  6. I usually expect a zener to fail shorted.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
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  7. It varies. :)

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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  8. Any hint of what it connects to?

    There are 2.3 V zeners but that would be unusual.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
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  9. James Sweet

    James Sweet Guest

    Me too, though I have seen them go open before, as well as change value or
    become leaky.
     
  10. electroninja

    electroninja Guest

    Gents: My computer wiz is standing by me and tells me that because of
    the way your messages are input to the system that many are imbeded not
    sequential as I had thought. I had missed the discussion about zener
    not zener, and OP says short, etc. I will try to keep up.

    I don't know if the zener is shorted or not--only that 2.3 volts was
    the reading across it--and it is a diode--and the circuit board lists
    it as Z02 vs Dxx as for other diodes on that same board. During my
    research on zeners today, the lowest voltage value I found was 3.3
    volts. So at what value do you recommed I start? Seems odd to me that a
    control board would use 3.3 volts to drive a relay circuit. Thoughts
    please?

    Do zener diodes have any markings on there cases to give any indication
    of their voltage rating or wattage?
     
  11. NSM

    NSM Guest

    | Gents: My computer wiz is standing by me and tells me that because of
    | the way your messages are input to the system that many are imbeded not
    | sequential as I had thought. I had missed the discussion about zener
    | not zener, and OP says short, etc. I will try to keep up.
    |
    | I don't know if the zener is shorted or not--only that 2.3 volts was
    | the reading across it--and it is a diode--and the circuit board lists
    | it as Z02 vs Dxx as for other diodes on that same board.

    That sure sounds like a zener. Can you measure the resistance forward and
    backwards with power off?

    | During my
    | research on zeners today, the lowest voltage value I found was 3.3
    | volts. So at what value do you recommed I start? Seems odd to me that a
    | control board would use 3.3 volts to drive a relay circuit. Thoughts
    | please?
    |
    | Do zener diodes have any markings on there cases to give any indication
    | of their voltage rating or wattage?

    Yes, but there's no simple standard IME. 3.3 volts is typical for power to a
    computer chip, though low for a controller like this.

    N
     
  12. electroninja

    electroninja Guest

    What voltage would you recommend I start at--3.3, 4.3, 5.1, 5.6 or
    higher? Also, Je ne sais pas ce que signifie IME?

    Thanks
     
  13. NSM

    NSM Guest

    | What voltage would you recommend I start at--3.3, 4.3, 5.1, 5.6 or
    | higher? Also, Je ne sais pas ce que signifie IME?

    http://40single.com/acronyms.html

    ....
    IIRC If I recall correctly
    IMCO In my considered opinion
    IME In my experience
    IMHO In My Humble Opinion
    IMNSHO In my not so humble opinion
    IMO In My Opinion
    ....

    Sorry, at this point I can't suggest a voltage. It's really a matter of
    experience and looking at what clues there are.

    N
     
  14. electroninja

    electroninja Guest

    Thanks, I'll remove the diode and give the circuit a quick voltage
    test.
    Any chance I could damage the LC4061 by pulling the diode and putting a
    VOM in the circuit? Ever heard of Queens University in Kingston, ahe?
     
  15. NSM

    NSM Guest

    | Thanks, I'll remove the diode and give the circuit a quick voltage
    | test.
    | Any chance I could damage the LC4061 by pulling the diode and putting a
    | VOM in the circuit?

    I would not do that.

    | Ever heard of Queens University in Kingston, ahe?

    Kingston ON?

    N
     
  16. DON'T do that. It could end up with much much greater voltage on the
    circuit and blow something out.

    What does the top of the zener connect to?

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
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  17. electroninja

    electroninja Guest

    Sam, your question was:

    Q. What does the top of the zener connect to?
    A. One end traces to a 25V electrolytic cap--other end traces to a 4
    pronged rectangular chip (S1VB ?) and eventually to the 32 pin on a
    38870L25 processor.

    In-circuit diode test:

    1. VOM attached diode leads--ohm meter reading started low and rose to
    1.6 meg ohms

    2. Leads were reversed and test repeated--initial reading neg number
    but rose to 1.38 meg ohms

    Diode is made of clear glass, black painted line around the circum at
    on end, has markings 180 or 18D on its casing--will have to remove to
    get clear image of # markings--

    Diodes glass body is cloudy--not shiny like others on the board
    Proposed Action: Remove diode and head to electronics supply store
     
  18. electroninja

    electroninja Guest

    Update:

    Zener removed and resistance check done with VOM on 2000K
    setting--zener measured 1.94 meg ohms in one direction and above 2 meg
    ohms in the other

    Diode case marking is 20B1--can someone interpret before I talk the
    Radio Shack sales rep

    Thanks
     
  19. Might be 18 V but only a guess at this point.
    Forget Radio Shack. They will be worse than useless.

    Need more details on circuit. If the end with the bar (cathode) comes
    from + on a 25 V cap, that could be a clue that it might be something
    like 18 V but not yet time to risk one like that.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
    | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

    Note: These links are hopefully temporary until we can sort out the excessive
    traffic on Repairfaq.org.

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name is included in the subject line. Or, you can
    contact me via the Feedback Form in the FAQs.
     
  20. electroninja

    electroninja Guest

    Sam,

    Just reviewed your paper on "Basic Testing of Semiconductor Devices..."
    and as a result retested diode. Analog readings were 4.7K and 2.7K
    ohms--still bad I assume.

    Will attempt to better trace circuit--also I've noticed Radio Shack has
    really changed from the old days--where is Allied Radio when I need them
     
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