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Thread: Fender Dual Showman....made in 1966

  1. #36
    Supporting Member bsco's Avatar
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    Quote Originally Posted by g1 View Post
    If they are solid smooth metal & brass shaft pots (not split knurled) I think they may be factory. I don't think they could get all the values needed with just one type of shaft so I think you end up with a mix, at least in some era/models.
    when I install the output tubes after the weekend, I was going to have a look at the numbers on the pots to see if I could make some sense out of the numbers printed on them....the plastic shafts are solid spline type.....thanks for that tid-bit of info....

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    Quote Originally Posted by bsco View Post
    ....I was going to have a look at the numbers on the pots to see if I could make some sense out of the numbers printed on them....the plastic shafts are solid spline type.....
    1966 was probably a transition year after the sale to CBS. I've seen mixed metal and plastic pots shafts in a lot of those amps from that time period, but I never bothered to check the pot codes to see what the difference was. You may find that the metal shafts are older and the plastic ones might have the new CBS part numbers stamped on them.

    Later amps had all plastic shafts and push on knobs. The older metal shafts could get banged without breaking. You might have to replace a cracked knob, but not a broken pot. The plastic ones were always breaking off, and replacing a pot on some of those amps took a complete disassembly of the front panel to get to it.

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  3. #38
    Supporting Member bsco's Avatar
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    Just back at this amp again.....tested the output tubes for shorts/leakage....checked ok......so I installed them.....powered it up and checked the bias to the output tubes....measures -49V.......checked the idle current.....the two inside tubes measure in the mid 30's mA and the outer two measure low 50's mA.....so I switched them around and the measurements followed the tubes......so there is one high and low on one side and the same on the other......Took some pics of those pots...hope they are clear enough.....I think I have one there that is wrong.......
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  4. #39
    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by bsco View Post
    Just back at this amp again.....tested the output tubes for shorts/leakage....checked ok......so I installed them.....powered it up and checked the bias to the output tubes....measures -49V.......checked the idle current.....the two inside tubes measure in the mid 30's mA and the outer two measure low 50's mA.....so I switched them around and the measurements followed the tubes......so there is one high and low on one side and the same on the other
    As Enzo has noted many times, Fender factory just plugged in sets of tubes without caring a fig about matching. So you have the choice of leaving the amp as is, or if you & your customer are striving for perfection and he's willing to spend then get a matched set.

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    Enjoy. Every. Sandwich.

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    Quote Originally Posted by bsco View Post
    Just back at this amp again.....tested the output tubes for shorts/leakage....checked ok......so I installed them.....powered it up and checked the bias to the output tubes....measures -49V.......checked the idle current.....the two inside tubes measure in the mid 30's mA and the outer two measure low 50's mA.....so I switched them around and the measurements followed the tubes......so there is one high and low on one side and the same on the other......Took some pics of those pots...hope they are clear enough.....I think I have one there that is wrong.......
    Click image for larger version. 

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    What is pic No.3?

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    - Own Opinions Only -

  6. #41
    Supporting Member bsco's Avatar
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    Pic #3 was something that was not supposed to be uploaded....I tried to delete it but couldn't get rid of it......
    Cheers

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  7. #42
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    Quote Originally Posted by Leo_Gnardo View Post
    As Enzo has noted many times, Fender factory just plugged in sets of tubes without caring a fig about matching. So you have the choice of leaving the amp as is, or if you & your customer are striving for perfection and he's willing to spend then get a matched set.
    The amp sounds good actually and I guess overall both sides are matched pretty close to each other......I'll check with the owner and see what he wants to do......
    Cheers

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  8. #43
    Supporting Member bsco's Avatar
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    Just checked with the owner and he is leaning towards a new matched set....he did ask me something...is 6L6GC a better fit than the 6L6WGB which are in there now?? I thought they were compatable but I could be wrong......so I figured I would ask here.....
    Cheers

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  9. #44
    Supporting Member bsco's Avatar
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    Looks like the owner is leaning towards a matched set of new tubes....he did ask me something that I am not sure about...he asked me which was better....the WGB's or the GC's.....and to be quite honest, I am not sure....suggestions??
    Cheers

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  10. #45
    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by bsco View Post
    Looks like the owner is leaning towards a matched set of new tubes....he did ask me something that I am not sure about...he asked me which was better....the WGB's or the GC's.....and to be quite honest, I am not sure....suggestions??
    Cheers
    I favor the GC generally. By WGB, is he referring to Philips/ECG 6L6WGB? Those - to me anyway - compare to real (not Russian or any other modern) 5881. Good tough tubes all right but may fall short of the mark if his style tends towards playing very loud. And the Philips these days sell for gold dust money while you can get perfectly competent 6L6GC at reasonable price from JJ or Shuguang. Some of us have had good success with Ruby tested & matched sets of Shuggies.

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    Enjoy. Every. Sandwich.

  11. #46
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    Thank you Leo....
    Cheers

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  12. #47
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    Ok. back again....the owner had decided to order all new tubes..even a match PI tube which was gold plated....cost something like $60.....anyway. they arrived to me last week and I installed them and set up the bias......then I ran into a problem which I will post here for anybody else that might have this issue...The amp worked great but the volume would fade out to nothing...all the voltages were ok. probing the plates of the PI showed the full B+ which was way too high....so I thought the tube was bad...tested ok on my tester...anyway, when probing the grids of the PI no sound....checked the cathode voltage and there was none...so I started to check all the components in the PI area...everything tested great....so after some head scratching, I just happened to measure the voltages on the plates of the pre-amp tubes....same high voltage there as well.....it turns out the the one of the heater wires which run from the pre-amp heater string to the first output tube was corroded and produced an intermittment bad connection...and when that happened, all the heaters would go out for the pre-amp tubes....once I got that taken care of, the amp worked great....I have it re-assembled and will run it for awhile on the bench before I return it to the customer....just posting the intermittment issue here in case somebody else runs into this problem with basically any multi-tubed amp.....
    Cheers

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  13. #48
    Supporting Member Jazz P Bass's Avatar
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    I have had preamp sockets give me headaches.

    The last one was the heater pins of the socket where brittle.
    This was after an EL34 puked.
    Probably sent B+ into the heater circuit.

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  14. #49
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    Quote Originally Posted by Jazz P Bass View Post
    I have had preamp sockets give me headaches.

    The last one was the heater pins of the socket where brittle.
    This was after an EL34 puked.
    Probably sent B+ into the heater circuit.
    That must have done a bit of damage.....

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