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Advice on vintage amp purchase

Discussion in 'Amp Input - Normal or Bright' started by JustABluesGuy, Nov 5, 2017.

  1. JustABluesGuy

    JustABluesGuy Strat-O-Master

    Age:
    60
    636
    Sep 3, 2016
    Houston, TX
    IMG_1839.JPG
    I'm going to try out a late 60s, early 70s Alamo Challenger amp for sale.

    I would really appreciate any advice anyone can give about what to watch out for. The owner thinks it is all original except for the tubes, and the speaker. It still has the 2 prong cord, so it seems likely that it is all original inside, though I hope to get a glimpse of the guts.

    He says it has NOS GE power tubes and a Weber 10a125 speaker, and he says it is in "fantastic" shape.

    Does anyone know what Ohms the output transformer on these expects? He said the Weber is 16 Ohms, but he doesn't have the original speaker, and I'm not sure that he is even the one that replaced it.

    I'm not too concerned as long as it is working right now. I'm sure it is way due for service, so I expect to have it worked on, so if it sounds good, I will grab it.

    I'm not too worried, since the price is very good. Any advice will be greatly appreciated!
     

  2. fezz parka

    fezz parka Wiggler of Sticks Strat-Talk Supporter

    Last edited: Nov 5, 2017
    JustABluesGuy likes this.

  3. Robins

    Robins Dr. Stratster Strat-Talk Supporter

    Dec 22, 2010
    Germany
    It has both taps (8 and 16Ohm). Some are set for 8 and some for 16Ohm. Check it, it is marked on the transformer.
    But that is a quick fix if needed (solder the cable coming from the output transformer to 16 instead of 8 - it is stamped on the transformer).
    [​IMG]

    All the best,
    Robin
     
    vid1900 and JustABluesGuy like this.

  4. Stevem

    Stevem Strat-O-Master

    842
    Sep 3, 2014
    NY
    Note that any multi tap output transformer will sound best and live longer when used on its highest impedance tap with a matching speaker!
    That amp is blessed with a good size OT for its wattage, sweet!
     
    Robins and JustABluesGuy like this.

  5. JustABluesGuy

    JustABluesGuy Strat-O-Master

    Age:
    60
    636
    Sep 3, 2016
    Houston, TX
    Thanks! I actually have some very similar 10" CTS drivers. They have bigger magnets though.
     

  6. JustABluesGuy

    JustABluesGuy Strat-O-Master

    Age:
    60
    636
    Sep 3, 2016
    Houston, TX
    I did not know that, thanks!
     

  7. JustABluesGuy

    JustABluesGuy Strat-O-Master

    Age:
    60
    636
    Sep 3, 2016
    Houston, TX

  8. JustABluesGuy

    JustABluesGuy Strat-O-Master

    Age:
    60
    636
    Sep 3, 2016
    Houston, TX
    I have other amps that accept 4,8, and 16 Ohms. I should use all of these at 16 Ohms when possible.

    It seems odd that they both come stock with 8 Ohm speakers, when they could have used 16 Ohms.

    Any ideas why they might do that? Thanks for the feedback!
     

  9. Tone Guru

    Tone Guru Senior Stratmaster

    Dec 13, 2011
    Music City TN

  10. fezz parka

    fezz parka Wiggler of Sticks Strat-Talk Supporter

    The cathode resistor is there, just no value. Not the first f'd up schem I've seen. :D
     

  11. Sarnodude

    Sarnodude Senior Stratmaster

    Sep 26, 2015
    Mukilteo
    Looks like an early Fender Champ schematic. Score!
     

  12. fezz parka

    fezz parka Wiggler of Sticks Strat-Talk Supporter

    The 5C1 was a screamer.

    [​IMG]
     

  13. Stevem

    Stevem Strat-O-Master

    842
    Sep 3, 2014
    NY
    I would sonically audition / try out removing that .002 cap across the primary side of the OT!

    And a audition a 50 uf Cathode bypass cap on the output tube also.