Home Amp Hoarders Need This?

Discussion in 'Shock Brother's DIY Amps' started by keithb7, Oct 11, 2019.

  1. keithb7

    keithb7 Friend of Leo's

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    6B7BEAC4-CB0F-49CE-9A20-784A8503BAE6.png

    All the cool amp folks definitely hang out here...School me on this new found object.

    I was walking through a hoarder’s garage. His family was cleaning up the place. I saw some old tube-era test equipment. I lit up! I saw “Sprague” which we generally associate as higher quality e-caps. I took a closer look. A Sprague TO-4 capacitor tester. About 1952 era. I paid $15.

    Surely I took it home! Tell me what this brings to vintage tube amp nut. So far I think I can actually test for leaking DC coupling caps. Also prove if 50 year old e-caps are really leaky. Not that I really care. My belief is all old e-caps get swapped out. I also think I can re-form old caps? Or slowly warm up old caps in barn find amps? Is that right? What else? Cool tool? Or???

    I’ve yet to try it. I found a manual and downloaded it. Tips and opinions appreciated.
     
    Last edited: Oct 11, 2019
  2. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

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    Worst case you could gut it and stuff it with 5e3 parts!

    Sure looks cool
     
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  3. keithb7

    keithb7 Friend of Leo's

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    071C20B8-04A1-4553-9612-1ACB46A1BE70.jpeg Wires inside are sure sketchy. The insulation is rubber-y soft, breaking up and falling off. Worse than most old amps I’ve ever seen.
     
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  4. keithb7

    keithb7 Friend of Leo's

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  5. 24 track

    24 track Doctor of Teleocity

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    I bet you cant wait to heat up your solder guns!

    cool frind!
     
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  6. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Cool!

    Looks like a bit of a fire hazard though.
     
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  7. jhundt

    jhundt Doctor of Teleocity

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    no problem, just set it in a bucket of water before you turn it on!
     
  8. tubelectron

    tubelectron Tele-Holic

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    Good find, indeed !

    It is interesting because it can test leaky capacitors under high voltage. :cool:

    To be operational, it will nearly need complete restoration, looking at the pics you provided. IMHO, do not try to power it up as is without tentatively insulating some wires... :eek:

    Moreover, probably most of the precision resistors and caps may have drifted, and need to be checked or replaced.

    Do not expect too much precision from this kind of RC bridge though, but it will be able - once restored and calibrated - to give you a good idea of the value of a cap and - most of all - an indication on its condition (D factor, DC leaks...).

    The schematic should be found here :

    http://bama.edebris.com/manuals/sprague/to4

    -tbln
     
  9. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

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    I hope we get a restoration thread!
     
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  10. FenderLover

    FenderLover Friend of Leo's

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    I'm sure you appreciate the irony in your cap tester needing its caps checked. I'd replace the electrolytics and then see if you can measure something with it.
     
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  11. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    So it can test electrolytics, and there are electrolytics in it...that need to be tested...but if you take them out to test them.....ooooh...I have a sharp pain behind my left eye now...
     
  12. jvin248

    jvin248 Poster Extraordinaire

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    Good thing the Sprague machine uses Sprague caps!


    .
     
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  13. King Fan

    King Fan Friend of Leo's

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    Yeh, I kinda pictured the cartoon animal on a cereal box holding a cereal box on which is pictured a cartoon animal holding...

    Seriously, Keith, replacing all that complex, totally rotten wiring *and* all the old components in order to have a device that sorta kinda tests old components which under the current logic of the universe you really want to replace anyway... I'll take the cereal box. :D
     
  14. Blue Bill

    Blue Bill Poster Extraordinaire

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    Don't worry, I checked it out with my new cap tester:

    amp.gif
     
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  15. archtop_fjk

    archtop_fjk Tele-Holic

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    But can it test itself to see if its own caps are still good?
     
  16. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

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    Does it have a double blind test setting?
     
  17. keithb7

    keithb7 Friend of Leo's

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    I was thinking it would be kinda fun for times when we get into the old "I don't change old caps, they are fine" argument. It might be fun to prove old e-caps that are garbage! Or, how about testing leaky coupling caps? Old leaky Astrons that are so beloved, some people would not dare replace them. Image if a guy somehow came into load of NOS Astron bumblebees? Wouldn't this old Sprague cap tester earn you a million $ if you could find the good ones and then sell em? lol. Better chance finding a unicorn maybe?

    I don't think I have the time or knowledge to restore this old Sprague time machine. How the heck would a person go about calibrating it? I would however sure like to pass it along to someone here who would like to host a restoration thread and educate us all. Anybody game to take this restoration over from me? @Axis29 @theprofessor @muchxs @telemnemonics @King Fan @thechad @robrob ? Any one? I can mail it. - Keith
     
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  18. dan40

    dan40 Tele-Afflicted

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    I purchased a very similar model (different manufacturer) a few years back and sent it to this fella for reconditioning and calibration. He had it back to me in less than ten days and the total cost was $125. I will occasionally use it to test for leakage on coupling caps. It will reform e-caps but I usually prefer to just replace those.

    https://tubesound.com/
     
  19. rob2

    rob2 Tele-Holic

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    ..awesome find!....hold onto it unless you can get a good home for it!
     
  20. muchxs

    muchxs Doctor of Teleocity

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    Sprague made the "bumblebee" caps. they were striped up to 1959 near as I can tell. A year or so later they became "Black Beauties", same caps only with the values printed plain as day on the sides.

    NOS Bumblebees generally test 50% high. that means the "Les Paul" caps are generally .033s and forget about the 400v rating. Who cares about 400v? They only see a fraction of a volt in a guitar tone circuit.

    For musicians who obsess over the precise .022uf value... what if The Motherlode of Golden Tone is actually the .033uf drifted value?

    BTW this is where George Gruhn started the "untouched solder joints and all original parts" Urban Legend. Yes, you can get away with drifted leaky caps in a guitar where they only see a fraction of a volt. No, old leaky caps aren't an asset in vintage guitar amps. They may be worth more dough cuz... well, because no one notices the Emporer is naked. Old worn out caps with sky high ESR just suck (tone) in vintage guitar amps.

    I went to an antique radio show yesterday. Got a couple 12AX7s, a dozen fuse holders and around a dozen milspec 9 pin miniature tube sockets with the nice nickel plated deep drawn brass shield bases.

    I'm thinking of building my own tube testers. Yeah, I've got tubes testers but I didn't build them. I want something that does 12AX7s quick 'n easy. Maybe another setup for 6V6s and 6L6s.

    I'm doing something similar in the cabinet shop. I'm buying more routers and getting set up for less saws, more routers.
     
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