Home Forums Radio Parts Wish List Looking for a L49B ballast tube.

Viewing 9 posts - 1 through 9 (of 9 total)
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  • #25301
    Ben Palmeri
    CVRS Member

    Well, the title says it all. Im looking for a L49B ballast tube for a Majestic Model 651.
    Thanks.

    #25302
    Dan Walker
    CVRS Member

    Hi Ben; I am looking for the same tube.

    From the research I have done, I have found that a sub for that tube is a L55B.
    I have not found one of those either.
    If you find a couple of these tubes please let me know.
    Dan in Calgary

    #25304
    Ben Palmeri
    CVRS Member

    Hi Dan,
    I guess ballast tubes weren’t made for a long time, so there aren’t many left.

    looks like I will have to fashion my own.

    Thanks ,
    Ben

    #25305
    John Greenland
    CVRS Member

    Hi Ben,
    I guess the question is how original did you want to keep the radio ?

    For example if you replace the ballast with a 50L6 and add a 330 ohm resistor across the heater you would effectively turn the tube into a 300 ma tube instead of a 150 ma tube.
    The resistor would be 7.5 watts and I am sure a 10 watt one would do very well.

    If you had the space, two 25L6’s in series would also work without a resistor but you need another tube socket.

    Just food for though from my slightly off brain !

    Good luck
    John G. VO1 CAT

    #25306
    Ben Palmeri
    CVRS Member

    I’m leaning toward the diode resistor combo. Radiated heat is drastically reduced, and the components will fit in the original L49B case maintaining original appearance. (Of the chassie at least)

    #25307
    John Greenland
    CVRS Member

    Ben ,

    Now you have me very curious.
    How are you using a diode in an AC circuit to drop 50 volts at 300 millamps ?

    Regards,
    John G.

    #25308
    Dan Walker
    CVRS Member

    Here is a link to ARF about this tube.. I am not planning on building a new tube , but the information is here for you guys that are.

    https://antiqueradios.com/forums/viewtopic.php?f=6&t=428992
    Dan in Calgary

    #25309
    Jim Sirtonski
    CVRS Member

    Hi Ben,

    The diode/dropper resistor is definitely an option but be aware that a diode failure in many cases will result in a in a short and should that happen it could take out other tubes in the string. You may want to investigate the use of a capacitor dropper. Have a look at this write-up on droppers https://www.vintage-radio.com/repair-restore-information/valve_dropper-calcs.html
    There are several technical articles available on the use of capacitors as droppers but few mention that you cannot use electrolytics or DC capacitors. You have to use an AC motor runtime capacitor. Good luck.

    Jim

    #25350
    Ben Palmeri
    CVRS Member

    Thanks everyone for the info. I’ve done both, dropper cap and diode. Both have there their modes of failure.
    I plan on using a 3A. diode, so its 10X bigger then is required. I’m going to look into adding fast blow fuse.

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