Dual Showman OT

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by steadygarcia, Oct 21, 2008.

  1. steadygarcia

    steadygarcia Member

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    I've purchased a '67 (BF) Dual Showman and it doesn't have the stock OT. It has an export OT so that it can be used in other countries. I'd like to get a stock one in there. I see that I can buy replacement OT's at places like Mojotone and Weber. Any suggestions or recommendations as to a good place to buy an OT? Should I be looking for an original; are originals (NOS) even available?
     
  2. slider313

    slider313 Silver Supporting Member

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    I believe you mean export power transformer? That's the one that would be voltage compatable,not the output tranny.
     
  3. steadygarcia

    steadygarcia Member

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    That makes sense. I haven't received the amp yet. The seller mentioned that,

    "The OT on the Dual Showman is not original. When I bought it there was an oversized transformer in it for some reason. It sounds good so I kept it."

    He also said that, "It has an export tranny so it can be used in other countries."

    So it sounds like neither the OT nor the power transformer are original then.
     
  4. tlpruitt

    tlpruitt Member

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    The power transformer could be original. Fender did make amps with "export" power transformers. From the quote you included above it sounds like the seller is mentioning that this amp has one of those export power transformers. It could have come from the Fender factory with that export power transformer.

    Fender amps with the factory export power transformers usually have a red knob on the back that allows you to select the voltage.
     
  5. steadygarcia

    steadygarcia Member

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    I did not know that. Here are a couple of photos that show it ... do you think this oculd be one of the originals?
    [​IMG]
    [​IMG]
     
  6. doctorx

    doctorx Member

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    Looks original to me.
     
  7. slider313

    slider313 Silver Supporting Member

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    Looks original to me also. No need to change it. Just set it on the 117V setting. It would be a good idea to update the electrolytic caps. That bias cap could be original.
     
  8. steadygarcia

    steadygarcia Member

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    Is the bias cap the big silver cap behind the transformer?

    A couple more gut shots here:

    [​IMG]
    [​IMG]
    [​IMG]
     
  9. tlpruitt

    tlpruitt Member

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    Also, I can't see the pix (damn firewall at work) but the showman came stock with a pretty large output transformer. The numbers on the outside of the output transformer will help determine whether it is original or not.
     
  10. Swarty

    Swarty Member

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    The Dual Showman has the same OT as a Twin Reverb... that one is much larger.
     
  11. Structo

    Structo Member

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    It looks like it has been recapped.
    The bias resistor has been replaced as well.

    Take the dog house can off the top, these are the power supply filters.
    Be careful not to touch anything as they can hold a charge and knock you on your ass.

    The screen resistors have also been replaced.

    I'd be a little scared with a voltage selector knob like that on the back.
    Seems like it would be easy to accidentally switch it unintentionally.
     
  12. steadygarcia

    steadygarcia Member

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    True. I guess I could always cover the switch somehow to prevent it. Or I could buy a replacement power transformer and get rid of the switch, but that's not cheap. When I finally get it, I'll check the power supply filters. Is the rust on the power transformer a concern?
     
  13. doctorx

    doctorx Member

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    Good idea, buy why not go one step further and eliminate the switch, hardwire it to 117 and shrinkwrap the rest he doesn't use?
     
  14. steadygarcia

    steadygarcia Member

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    I'm not all that concerned about it really. I honestly didn't even think about it until Structo brought it up. Maybe a piece of duct tape over top of the switch? :)
     
  15. AR-305

    AR-305 Member

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    I had one of those for a while. It said 85 watts above the speaker jack but man it was the loudest amp I've ever owned. That's another of the "wish I hadn't sold that one" collection.
     
  16. steadygarcia

    steadygarcia Member

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    I don't know if you can tell from the pics that I posted earlier in this thread, but are there any measurements I can take on that oversized, non-original OT to see whether I should keep it or replace it with an original? in other words, is there some spec related to it that will tell me if it's harming the amp? My understanding is that generally a larger OT can mean bigger bottom end. So perhaps I should just keep the large OT someone put into the Dual Showman.
     
  17. mr coffee

    mr coffee Gold Supporting Member

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    that is the wrong OT fo' sure..yours looks like a hammond..not thats that bad..

    [​IMG]
     
  18. steadygarcia

    steadygarcia Member

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    So I don't need to be worried about causing any damage with a bigger OT?
     
  19. mr coffee

    mr coffee Gold Supporting Member

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    as long as the impedances match (actual connected to the four ohm tap of the OT)
     
  20. gldtp99

    gldtp99 Member

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    I have two vintage Fenders with the Export Voltage Switch on the back panel and i've never seen a reason to change anything about the Voltage Switch----just set it on 117V and check it before you plug in if you move the amp anywhere.
    On one Dual Showman i had (SF non-Export model) i replaced the orig OT with a Heyboer Showman/Twin Reverb OT that had 4/8/16 ohm output taps---it sounded great and could be used safely with almost any speaker cab.
    Heyboer would make one of these Showman 4/8/16 ohm OT's up if you called them---i've got a BF Showman with a re-wound OT ( 8 ohms--by ?) and i've considered getting another Heyboer 4/8/16 OT but the amp sounds so good the way it is that i haven't been in a rush to pick up the phone to call Heyboer.
    http://www.heyboertransformers.com/tubeamps.shtml
     

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