Old Components.....

Discussion in 'General Electronics Chat' started by Lancester, Feb 5, 2011.

  1. Lancester

    Thread Starter New Member

    Feb 5, 2011
    2
    0
    Hello all. Newbie here.
    I am about to beging construction on a Heathkit SA-2 Tube audio amplifier that was originally sold in 1960. I am wondering what the "shelf life" of electronic components, mainly capacitors, is. Of course if this kit had been built back then & I was planning to use it I would be re-capping the entire unit.


    [​IMG]
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,019
    Probably not worth building just for the tubes alone Tubes have a vacuum just like a light bulb. That vacuum has probably been breached a long time ago.

    Resistors will even change their value over many years.
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    The tubes would certainly be worth testing, or at least not discarded out of hand unless they have obviously leaked. Visible cracks or whitening of the usually metallic getter deposits would be clear pointers to air entry. Considerable numbers of tubes have survived in working order from as far back as the 1920s, so it is really not impossible for 1960's devices still to be good.

    As for the capacitors, the electrolytics should certainly not be used without re-forming, a process which might or might not work. How good would their performance and life expectancy be after all that bother? Any paper capacitors should be regarded with the very greatest of suspicion. These things are horribly prone to going leaky, even if stored under dry conditions. Capacitor failure can lead to burnt-out tubes and transformers, so maybe the originals would be better not used, even if apparently good.

    The resistors at least are simpler to test. If you found that many had drifted, perhaps get them all changed.

    Actually, I think the main things that are of value in such a kit are the transformers, chassis, and other metalwork. Are you sure they are OK?
     
  4. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    I am still running a vacume tube kit i built in the early 60's. Caps probably should be reformed -- brought up to voltage slowly and/or thru a high resistance. I would go for it. The idea that thing die so easily is overblown. Some tubes from the 20's are still in use.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Be very gentle with the tubes/valves. Placing strain on the pins can and will cause the hermetic seals to leak. Even a very small leak will kill a tube.

    The old brown-body cylindrical carbon resistors are quite prone to shifting their values over time; they almost always increase in value. I had a number of mil-spec precision resistors left over from a project back in the 70's; they were manufactured in the late 1960s and sealed in moisture-resistant packs of 10. I was quite surprised to find that some of them read more than double their markings; these were 1% tolerance resistors.

    By comparison, the more modern tan-bodied dumbbell-shaped carbon film resistors are quite stable; I have some that I bought back in the early 1980s and they are still within tolerance.
     
  6. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,019
    I stand corrected. I did not think the seals would have lasted that long.


    Anyone have a tube tester? You uses to be able to find them in just about any drugstore when I was younger. :) I had one, can't remember what happened to it. I am thinking it was just on loan.
     
  7. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Tubes rarely wear out if not used, the electrolytics will though.
     
  8. jgessling

    Active Member

    Jul 31, 2009
    74
    14
    You might want to get on ebay and search for "unbuilt Heathkit" to see how much your kit could be worth. If you have the box and all the parts and manual these things go for hundreds if not thousands of dollars. I'm suggesting you think about selling it and using the cash for more modern electronic efforts. The available microcontrollers are really cheap and can be used to build amazing things as an example.

    Regards, Jim
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,652
    2,348
  10. Lancester

    Thread Starter New Member

    Feb 5, 2011
    2
    0

    Speaking of....

    http://cgi.ebay.com/ws/eBayISAPI.dl...YY8UbEU%3D&viewitem=&sspagename=STRK:MEWNX:IT
     
  11. Rbeckett

    Member

    Sep 3, 2010
    205
    32
    That is actually a very good idea to see what the value of the heathkit is and to order several lesser skill required kits that you will gain some confidence in as well as soldering experience along the way. The heathkits were notoriously heavy with point to point wiring and many kits were attempted to be assembled but failed due to the hobbyist exceeding his or her skill levels. Just the opinion of an old kit builder from another hobby who learned the hard way. I now have several RC airoplanes that I cannot safely fly due to their complexity and speed exceeding my lagging abilities. Be carefull and go slow learning the basics first, then move on to more complex devices and projects.
    Bob
     
  12. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
    2,831
    89
    Hi, marshall seeing you after long time...!!!!
     
  13. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Last spring I bought an RC Piper Cub electric airplane. I flew it in the park and in school yards for hundreds or thousands of flights. It wore out 10 Li-po battery cells and 2 brushed motors.
    It flies at only 10km to 20km (6.2mph to 12.4mph) with no wind and frequently "hovers' when flying into the wind.
    It weights less than 1 ounce with battery so it doesn't hurt when it hits somebody. Its propeller chopped at my fingers many times and also doesn't hurt.

    My RC P-51 Mustang electric airplane is another story. It can fly dangerously fast so I keep it up high enough so it doesn't hurt anybody. It weighs a little more than 1 ounce with battery.
     
  14. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Hi Rritesh, learn anything new lately?
     
  15. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
    2,831
    89
    Yaaa, i am completing my college project.:D
     
  16. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    He is learning about obsolete 40+ years old parts.
    Modern parts are not available over there.
    Half of the time ordinary electricity is not even available over there.
    And his teacher is teaching nothing.
     
  17. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Perhaps, but he has the incentive to learn.
     
Loading...