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Please help with component Identification

Discussion in 'Electronic Design' started by Stan, Feb 15, 2007.

  1. Stan

    Stan Guest

    Hi, I posted on here a few days ago but so far have no response. I now
    have photo's available at http://www.stanleyes.ndo.co.uk/ .

    If anyone can ID this component i'd appreciate it.

    There is more info in my previous posting "Help Component ID, TVS??"

    Thanks
    Stan
     
  2. Surely it is R802, a resistor?




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  3. Baron

    Baron Guest

    It looks like a spark gap surge suppressor !
     
  4. Tom Bruhns

    Tom Bruhns Guest

    I'd guess it's a MOV -- metal oxide varistor -- or a close relative,
    that as you suspect, is a transient voltage suppressor. The symbol on
    the PC board bottom looks right for that to me. I have no idea about
    ratings. You might do a search of MOV/TVS manufacturers to see if any
    have components packaged and labelled that way.

    Cheers,
    Tom
     
  5. I'm going off the bottom of the board. The Z801 is the MOV (big red blob).

    The glass casing is odd.
     
  6. Tom Bruhns

    Tom Bruhns Guest

    Hi HJS,

    Have another closer look. When I look at it, it seems clear (bottom
    of board picture) that Z801 is further from the relay than R802. On
    the top of the board, the "big red blob" is the one closer to the
    relay. Therefore, I conclude that the glass-encased guy is the MOV,
    or whatever. Either that or work has gotten to me and I've gone blind/
    crazy/both.

    Cheers,
    Tom
     
  7. Robert Baer

    Robert Baer Guest

    It is clear that R803, drawn as a resistor, is the "red blob" has the
    looks and size of a MOV suppressor and that Z801, drawn as a suppressor
    (looks like the removed device) appears more like a glass encapsulated
    resistor which appear to be rather rare.
    Methinks the placement of the parts are bass ackwards.
     
  8. No, the big red blob is clearly an MOV. I suspect the Z801 ID was moved
    because it couldn't be printed where needed. The glass case is
    characteristic of a diode or zener, but the inside looks like a carbon film
    resistor. Confusing.

    Doesn't the R802 ID below line up with the removed unknown part?



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  9. Stan

    Stan Guest

    Tom & HJS

    Tom is correct, Z801 is the label for the mystery glass cased
    component. It is labelled both top and bottom of the board and is
    furthest from the relay. Just to be pedantic..you seem to be
    mistakingly referring to R802 which is not in the photo's, i think you
    mean R803. Also, unless i'm very much mistaken R803 (the big red blob)
    is not a MOV but a PTC Thermistor (Posistor). I have removed this from
    the PCB and at room temperature it has a resistance of 8Ohm. If i
    leave it sat on a heater for a while and retest it had changed to
    80Ohm. I believe this 10x range is what you would expect from a
    Thermistor/Posistor.( I guess this blows the theory that the red blob
    is a MOV and the labels have been switched.)
    I think this is pretty standard degauss circuitry, On activating
    degauss, relay RL801 closes allowing AC current to flow through the
    degauss coil, current flows through the circuit causing heating in the
    thermistor, this causes the thermistor resistance to gradually
    increases reducing the current flow.... Its just this Z801 i'm not
    sure about, it could be functioning perfectly OK but i'm not used to
    observing sparks in a component even if they are small and contained.
    As you can see on the bottom of the board, the mystery Z801 is
    connected across one pair of NO relay contacts. I think this makes it
    likely the device is some kind of suppression device.

    Robert

    Please note the photo's were taken before i removed any components
    from the board so the chances that the two components have been
    switched are minimal. Also note that the pad layout's match the
    components, Z801 pads are in line to match the mystery glass
    component, R803 has offset pads matching the offset legs of the
    thermistor.

    Baron

    Was your suggestion tongue in cheek? No offence if not, but the name
    sounds too close a match to my previous description for it to be true.
    I hope i'm wrong, but searching for "spark gap surge suppressor" on
    google returns very few hits.

    My thoughts are that it could be:

    1. A bipolar TVS. But the glass casing is unusual, i can't find
    anything similar on TVS manufacturers websites.
    2. A resistor, again in unusual packaging. If its burnt out the
    voltage could be causing the sparks seen jumping across the inner
    cylinder.
    3. Dare i say it "spark gap suppressor"? Who manufacturers such
    devices?

    Thanks everyone, any more thoughts are gratefully received.
    Stan
     
  10. John

    John Guest

    For search terms, try gas discharge and/or gas plasma suppressors

    Raychem, Tyco, Littlefuse.

    Maybe this will get you going: http://www.mouser.com/catalog/629/457.pdf

    Good luck!

    John
     
  11. But all of those look like what they are!



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  12. Rich Grise

    Rich Grise Guest

    It doesn't look like any MOV I've ever seen. Actually, it looks like
    a multilayer chip capacitor (MLCC?) in a glass envelope.

    I have no idea how to read the stripes, however. )-;

    Thanks,
    Rich
     
  13. Rich Grise

    Rich Grise Guest

    That pretty much takes care of that - it's a MLCC in a glass package.
    Maybe designed to be very lossy, like a whole snubber in one 2-pin part.

    Cheers!
    Rich
     
  14. it looks like a carbon film resistor in a glass package. That is very
    bizarre.


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  15. It doesn't look like anything I've ever seen. Until it is ID'd you've got
    me.



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  16. Eeyore

    Eeyore Guest

    Did you not see the legent on the reverse of the pcb ?

    I imagine it must be some kind of breakdown diode.

    Graham
     
  17. Guest

    It's a Sg-Gap sg99b3en.
     
  18. Robert Baer

    Robert Baer Guest

    I think that is what i said, that the red thinggie is truly a MOV,
    but if you look at the designations at tbe bottom of the board where
    there are *no* "space limitations", the R and Z designators are
    bass-ackwards.
     
  19. Robert Baer

    Robert Baer Guest

    I agree, that glass encapsulation is rare and unusual.
    The "most recent" glass encapsulated resistors i saw was about 30 or
    so years ago, and those were Victoreen gigohm and up resistors for
    ionization chamber electronics and similar very low current tube devices.
     
  20. Robert Baer

    Robert Baer Guest

    ?? A search on all of that or either half gave nothing.
    Whazzit?
     
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