SB-220 3-500z

Discussion in '"Boat Anchor" & Classic Equipment' started by VE5PMG, Oct 2, 2010.

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  1. W8JI

    W8JI Ham Member QRZ Page

    I hope you told the person who shipped the amplifier that way he destroyed the tube(s) through his carelessness.

    While one tube is broken, the other could be damaged internally.

    Tell him in a nice way he made a gross mistake, but be sure to tell him so he learns some common sense in packing and shipping. You have my permission to tell him someone in the business for 35 years says he is "a fool and should pay for new tubes for you".

    I almost never find a 3-500Z that lives when shipped in the socket. Duh.
     
  2. VE5PMG

    VE5PMG Ham Member QRZ Page

    Thank to all for your replies. Was my first post in these forums, your wise responses, are all very much appreciated. Thank you. Its a bit of a story but i may be on my own for this we'll see. Based on the responses i think i may opt to purchase a pair of rfp's that way the amp will have a whole new beggining. Its got a bunch of the mods and is nice case condition. The only other exception is it comes from a smoked in environment, i could smell it as soon as i opened the box so i have a bit of cleaning to do to get it to pristine. Im an ex smoker so im real fussy. It vary well will be my first big gun and my last, unless a better one comes along. Was a shame this happened. Its nice to know i could at lease try the remaining eimac along side a rfp to at least see if it will load up. Then either keep as a spare or get a bit of recovery if its still good. The paint on it is still very much red, indicating low use i understand. Anyway im rambling. Thanks again Gents! maybe catch you on the air one day.
    Keep up the great responses and feedback, this newbie for one if greatly appreciative.
    God Bless and 73
    perry ve5pmg
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Good luck with the amp! SB220's a solid design.

    I'd be wary and cautious to test everything carefully. Anyone who ships an amp like that with the tubes installed is either careless or doesn't know much about amplifiers; as such, there could be other latent problems.
     
  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    Hi Perry,

    I've owned an SB220 since the mid 70s. The tubes finally gave up the ghost after loss of cooling (it wasn't a pretty picture). I've been using RF Parts 3-500ZGs for several years without problems (I bought a matched pair). I don't know that I'd want to try mixing tubes for other than testing purposes. One may have more gain than the other, and "hog" more Ip (and run hotter). FWIW, this is what a socket looks like when you lose cooling:

    [​IMG]
    (click for larger image)

    Note the good grid contact on the left and the overheated tensioner on the bad filament contact on the right. On the bad contact, the contacts don't quite close. You need good contact for 14.5A of filament current.

    It's been said that the Heath cooling scheme is pretty good but, there's not much overhead. If the fan motor doesn't turn freely, the bearings need cleaning & reoiling. If the bearings are loose, it's time for a new motor. Grainger sells the Dayton 4M070, which will move more air. K5DBX came up with a shroud that minimizes fan noise. See the last post in this QRZ thread. I haven't tried it (yet).
     
  5. W8JI

    W8JI Ham Member QRZ Page

    Red paint means low temperature operation, not low hours.

    The paint Eimac used was designed to change when tube temperature ratings were exceeded. I'm sure now it is just any old paint.
     
  6. KI6DCB

    KI6DCB Ham Member QRZ Page


    Not just internally, but any acceleration that was sufficient to break one tube (assuming that there was nothing adrift within the amplifier to act as a bullet) was probably sufficient to have caused the seal around one or more pins of the "surviving" tube to fail.

    I agree with Tom; he should buy you new tubes...or, at least, go 50-50 with you.
     
  7. KM1H

    KM1H Ham Member QRZ Page

    A few years ago I had an AL-80A sent in for 6M conversion and the tube was left in the socket with just minimum packing around it.

    It arrived hanging by the plate cap. All pins were sheared off and the anode was floating loose. Vacuum was still good!

    Carl
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    "Other than that, Mrs. Lincoln, how was the show?":p
     
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