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Capacitance Meter Recommendation

Discussion in 'Electronic Repair' started by Nomen Nescio, Jun 26, 2005.

  1. Nomen Nescio

    Nomen Nescio Guest

    I'm just starting the process of bringing back from the dead a very old
    1950's RCA color television. The CTC-7 chassis is very ugly looking, with
    over 75 paper capacitors. There are also two Sprague can-type
    electrolytics, 3 caps in each can. Will have to make something to replace.
    Powering on is out of the question until I can replace numerous components.

    I want to buy a capacitance meter to check both the caps that I'm replacing
    and the replacement parts I will install. I've been looking at a BK
    Precision 810c Capacitance Meter. Or maybe I'll buy a Fluke 177. But then
    I read this from a post in 2002:

    "don't expect the Capacitance measurements (of a DMM) to equal that of even
    the cheapest C meter. Even on the "expensive" meters." Paul Grohe,
    sci.electronics.basics

    My concern is that the capacitor checker function built into a
    multi-purpose DMM isn't as good as a stand-alone capacitance meter. Is
    there any truth to this statement?
     
  2. John Bachman

    John Bachman Guest

    Nearly everyone who is into restoring old radios or TV's (myself
    included) replace all of the paper caps with polypropylenes or mylars
    and all of the electrolytics with new ones. If one of them is still
    good, it is likely to fail soon, so why not just replace them all?

    Do that and you do not need a meter as the new caps are surely good.

    But, if you really want a cap meter I can offer the ESR60 which
    measures ESR and value at US$149.00. See
    www.anatekcorp.com/testequipment/atlasesr60.htm for details.

    John
    The Electronic Repair Center at www.anatekcorp.com
     
  3. If you want to verify electrolytic capacitors, you have to be able to
    check the ESR.

    Tom
     
  4. Nomen Nescio

    Nomen Nescio Guest

    There are only three electrolytics in the entire set, one has already been
    replaced. The remaining caps are paper, mica, and ceramic. From my
    reading up on caps, it's the paper ones that need replacement. Over the
    years some of the paper caps have been replaced with orange drops. So I
    don't have to do all of them. Still, it's a literal bird's nest of wires
    on the underside of the chassis. Seems like back in the 1950's, the way a
    TV was designed (or maybe it was just RCA) such that one component wouldn't
    short out another, was to simply bend the leads so that nothing touches.
    Frightening! The TV may also have transformer problems, although the
    flyback looks very clean, with no signs of arcing.

    At one time I was very good at troubleshooting an AN/SPS-10 surface search
    radar, so I'm confident I'll be able to get this thing showing a color
    peacock once again. My main focus will be to get the power supply area
    cleaned up. After that I'll work on the deflection circuits. Only when I
    can get some kind of raster will I then turn to the video and color areas.

    I've read about the ESR meters, just never used one before. And don't
    quite understand how it could work with a cap in circuit, as other
    components would effect the values of the component under test (like an
    inductor in parallel with the capacitor).
     
  5. Nomen Nescio

    Nomen Nescio Guest

    According to the specifications for your meter, the minimum Capacitance
    measurement range is 1uF. How would this meter work for paper capacitors,
    when all of the fixed paper capacitors in my set are all under 1uF, with
    the smallest being .0018uF and the largest being .47uF. Just doesn't seem
    the appropriate product for my application.
     
  6. Guest

    Why not tuen on the set and see what happens. The vacuum tube color
    sets, which I worked on in the 50's to go thru college, were very
    forgiving of temporary overloads, etc. If you are familiear with
    tubes, you understand there is much more margin than with transistors
    as far as temporary overloads are concerned.

    H. R.(Bob) Hofmann
     
  7. John Bachman

    John Bachman Guest

    First we have to establish that we are talking about two very
    different applications: old TV/radio restoration and ESR.

    When your TV was designed no one worried much about ESR, it just was
    not an important characteristic of capacitors, electrolytic and
    otherwise. So ESR measurement is not a big deal in those situations.
    I only mentioned it thinking that you might have other applications in
    which ESR measurement would be useful.

    You are correct in that ESR is affected by other components in the
    circuit. Most ESR measurements are made on electrolytic filter
    capacitors, not frequency sensitive circuits. In those case, the ESR
    can be measured in-circuit as long as the meter does not forward bias
    any semiconductors in the circuit. Not a problem with 50's TVs :)

    John
     
  8. John Bachman

    John Bachman Guest

    See my post to your other question.

    Yes, the ESR60 will not measure the value of the paper capacitors you
    are dealing with.

    John
     
  9. Nomen Nescio

    Nomen Nescio Guest

    Believe me, this set ain't in power-on condition. I was told that the set
    was broken, hadn't been turned on in years, sat in an unheated garage for
    years, and the power cord was snipped off. Upon a visual inspection, the
    horizontal output tube was up to air (getter all white), and the chassis
    was only partially bolted in place, bolts finger tight, another bolt
    rolling around loose inside, along with several tube shields. The main
    power transformer has leaked a dark brown goo down on the chassis (the
    chassis sits vertically on its side), with the video board all gunked up.
    The CRT board took a nice hit, cracking the neck socket. Fortunately the
    wires to the socket are all intact, and the vacuum is still there. Believe
    me, there have been many hands in this set, with many modifications from
    the schematic I've obtained. The CRT is a 21FBP22, replacing the original
    21CYP22. The old man who used to own it must have been in love with the
    thing, because it appears the CRT has been exchanged twice from when it was
    purchased in 1957. Looks like around the mid 1970's the repair shop told
    the guy to give it a decent burial, because that's when the repair tags
    end. They probably didn't want to work on it anymore.

    So anyway, I'm going to give this my best shot. Have a whole bunch of caps
    on order. Once I get the power supply cleaned up, I may attempt to fire it
    up (only talking figuratively here:) and see if I can get raster....
     
  10. Dolemite

    Dolemite Guest

    Don`t know much about TV`s,but how good would a 1950`s TV picture look
    compared to say, a new HDTV? just wondering wouldn`t it be a lot more worth
    repairing a broken HDTV or plasma TV? were TV`s built a lot better in the
    50`s?
     
  11. Ken Weitzel

    Ken Weitzel Guest

    Hi...

    Memories, my (must be young) friend, memories :)

    Gee, even reading about it brings 'em back. Had forgotten
    about those boiling hot shields on the if's :) And trying
    to find the key to put hot tubes back in the tuner. And
    squeezing wax paper caps gently with a pair of long nose to
    test them.

    And cleaning tuner contacts... and fine tuning the fine
    tuning... and real solid wood cabinets that weighed tons...
    and antennas on the roof... more and more keeps flooding back :)

    Memories, wonderful memories :)

    Take care.

    Ken
     
  12. quietguy

    quietguy Guest

    Surely you would replace all those caps as a matter of course, as well as the
    high value resisters

    David
     
  13. Jamie

    Jamie Guest

    you will also need a variable HV supply to check for leakage, more like
    a HI-POT unit.
     
  14. Jamie

    Jamie Guest

    you may find that the flyback is out in left field.
    good luck in locating another.
    it was a common problem of having bad flyback transformers
    for various reasons.
    one of the common problems was losing the horizontal drive, the tube
    would heat up thus popping it self during its melt down and heating the
    heck out of the flyback melting the wax while in process.
     
  15. Nomen Nescio

    Nomen Nescio Guest

    Well sure, if I wanted a new color TV, I could easily go over to Best Buy
    and get a new Sony Wega 16:9. But that's not that point. A 1950's color
    TV is a rare and beautiful thing indeed:

    http://www.novia.net/~ereitan/Gallery/Gallery_Index.html

    People throughout the country and world restore all sorts of old
    technologies. Here's one I found the other day. So fascinating:

    http://www.automaticwasher.org/
     
  16. John Bachman

    John Bachman Guest

    Slide over to rec.antiques.radio+phono and see how many people are
    into restoration of old electronics. It might give you a different
    perspective.

    John
     
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