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How to measure High tension of a FBT. . .

Discussion in 'Electronic Repair' started by Starflex, Mar 29, 2007.

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  1. Starflex

    Starflex Guest

    Hello!
    If you read the post below (sorry for two post....), I have a E500 Sony
    monitor.
    I have replaced the varistor that regulate hte high tension of the
    FBT...because the previous is quite "cooked"....
    So, now I must regulate the high tension to the valour of 27 kV.
    I don't have the high tension probe for my meter (they are quite expensive,
    and I don' t want purchase their....).
    There is any safe method (for example, using a voltage partitor, or
    something other!) to measure this voltage with a standard meter?
    Thank you!
     
  2. You could build a voltage divider, but to do it safely it would require more
    effort and cost than the probe.

    Used units are out there ... ebay?
     
  3. Starflex

    Starflex Guest

    I think...
    27KV requires a good isolation...
    Uhmm...only the high voltage probe...very difficult to find for my Protek
    608...
    I can search, probably, a full meter ...but I use it only this time..
    probably, the cheapest solution is to ask help to an alectric laboratory.. I
    think that probably is the better solution, finally....
     
  4. Sofie

    Sofie Guest

    Starflex:
    Gosh.... I would forget about a dedicated, add on, HV probe for your
    Protek.... instead, get a stand alone high voltage probe with meter and
    ground clip... brand new around $60 - $70 from MCM and used ones are VERY
    very much cheaper on Ebay.... it appears that you have not tried an Ebay
    search yet??? .... or a google search yet???? .... Lots of stuff to
    look at regarding HV probes.
    And, as a very FIRST resort since you are on the SCI.ELECTRONICS.REPAIR
    newsgroup you should have FIRST gone to the REPAIRFAQS that discuss HV
    probes... safety, design and so on.... there is even a sample circuit there.
    I found this article in just a minute or two. Go to this link:
    http://www.repairfaq.org/REPAIR/F_hvprobe.html

    and the following two Ebay items in less than a minute:
    (I searched for "high voltage probe" ..... obviously)
    http://cgi.ebay.com/Leader-high-voltage-meter-probe-LHM-80B-n-r_W0QQitemZ270
    104401076QQcategoryZ25411QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    http://cgi.ebay.com/40-KV-HIGH-VOLTAGE-PROBE-400-MA-DC-NO-RESERVE_W0QQitemZ2
    50098396960QQcategoryZ50971QQrdZ1QQcmdZViewItem

    If you can pick up a used Ebay HV Probe for just a few bucks it would most
    likely be much cheaper and much safer that building your own.

    Best Regards,

    Daniel Sofie
    Electronics Supply & Repair
    - - - -
    - - - - -



    snipped:
     
  5. Guest



    Go to the website for this newsgroup at
    http://www.repairfaq.org/
    there, with a little search time you will find what you are looking
    for.

    Also there are alot of cheap used high voltage probes on ebay all the
    time, many of them do not require a meter or scope to hook up to, they
    have their own meter built in, much handier and safer?

    electricitym
     
  6. spam

    spam Guest

    Let's see... a piece of plastic pipe about two feet long... a hundred 1
    meg resistors soldered in series... 100 megohms... one end connected to
    ground, the other to 27 kV... that's a current draw of only 270
    microamps... and the voltage across the resistor connected to ground
    will be only 270 volts.
     
  7. James Sweet

    James Sweet Guest


    I found a probe on ebay, but in a pinch you can build one out of a bunch
    of 10 meg resistors in a piece of 1/2" PVC pipe filled with mineral oil.
    Shouldn't cost you more than 10 bucks to make.

    Another option is to measure one of the other voltages produced by the
    flyback, usually there's several and they follow the HV pretty closely.
     
  8. JANA

    JANA Guest

    You need an HV probe or a stand alone HV meter for testing CRT high tension.
    You will not easily or feasibly be able to build your own. There are some
    very serious safety issues involved if you were to try to build your own. If
    you are going to be in the business of servicing TV sets and monitors, then
    you will have to buy the necessary tools to do the job.

    --

    JANA
    _____


    Hello!
    If you read the post below (sorry for two post....), I have a E500 Sony
    monitor.
    I have replaced the varistor that regulate hte high tension of the
    FBT...because the previous is quite "cooked"....
    So, now I must regulate the high tension to the valour of 27 kV.
    I don't have the high tension probe for my meter (they are quite expensive,
    and I don' t want purchase their....).
    There is any safe method (for example, using a voltage partitor, or
    something other!) to measure this voltage with a standard meter?
    Thank you!
     
  9. Ray

    Ray Guest

    I would be very leery about the accuracy of a probe bought on Ebay. The
    voltage divider resistors in these probes are very fragile, sort of a
    glasslike construction.
    If the probe gets dropped, or banged the resistors can get hairline cracks,
    and the readings will be way off.
     
  10. Jim Yanik

    Jim Yanik Guest

    Too much load. The Fluke HV probe is 1000 Megohms,rated to 50KV,IIRC.
     
  11. Starflex

    Starflex Guest

    Sofie wrote:
    [snip]

    Hi Sofie, and many thanks for your reply.
    Before searching in Google, I prefer to ask to a "real man" if it is safety
    or not: this is "my first monitor" and I'm not very sure of what I can do or
    not.
    I have already search on Ebay about High Voltage meter, about two weeks
    ago...
    Yes, the price that I can find -especially for used item- is very low...but
    I live in Italy..and there is the shipping cost!! :)
    Consider that, if i choose an economical shipping, it cost about 20
    dollars..and it requires VERY OFTEN three months (!!). In the better chance,
    it arrive in "only" 8 weeks.
    If I choose, instead, a faster shipping, the cost is higher...40 dollars.
    So, the total cost is quite high, for a item that probably I'll use once in
    my life..!
    I'm not a "repair man", I don't work in a laburatory: I'm only a student, of
    course, with the passion for those things..but only a passion...and the
    CRT's monitor are almost dead...
    Thank you for the link about the FAQ's: I don't know that this newsgroup had
    the faq's...!
    So, finally...thank you for your reply, and sorry for the "stupid" question!
     
  12. Starflex

    Starflex Guest

    ....some sellers don't sent to Italy, or the shipping cost is too high, if I
    want to receive it in a resonable time.... :-(
     
  13. Starflex

    Starflex Guest

    I had seen many items, but I have a doubt..and I've found a seller that can
    ship it to Italy for only 25 $, S&H included.
    I had seen that all the items included the meter (probably, a galvanometer),
    but it is quite little.
    I think that is very difficult to read a valour of 27kV, +- 0,1 kv.
    Is only my imprerssion, or it is really correct..?
     
  14. Ray

    Ray Guest

    It is no harder to read 27 kv on a meter than to read any voltage on any
    other meter. Usualy around 27 kv would be in the most accurate area of the
    meter.
    But, it would be good to test the meter against a known voltage.
    We used to have 4 or 5 of these, but kept one locked up as a standard to
    check against.
     
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