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6V6 As Rectifier

Discussion in 'Shock Brother's DIY Amps' started by robrob, Apr 17, 2021.

  1. robrob

    robrob Poster Extraordinaire Ad Free Member

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    I just got an interesting email from a Champ builder. His amp was up and running normally when he changed tubes and accidentally installed another 6V6 into the rectifier socket. The amazing thing is the amp functioned but max volume was very much lower than normal.

    I'm amazed that the 6V6 worked as a rectifier but his functioning Champ proves that it can happen. With a 6V6 in the rectifier socket you would have half the 5v heater voltage connected to a 6V6 heater filament (pin 2). The other 5v heater wire would be connected to the 6V6 cathode (I don't understand how the heaters worked at all).

    The screen grid would be connected to one of the high voltage AC wires (the other wire would be connected to 6V6 pin 6 no connection).

    The 6V6 cathode would be connected to the B+ wire (which is normal).

    So you'd have low filament heat and the screen pulling electrons from the cathode. I'm shocked the screen grid didn't melt from the relatively high current pulled through it but the amp ran like that for a few minutes until he noticed the low max volume.
     
  2. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    I had a guy bring an amp over with the "it doesn't work" and found he was tube swapping and put in two 6v6 tubes instead of a 5y3/6v6 in his amp. This one didn't make any noise.
     
  3. sds1

    sds1 Tele-Afflicted

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    You know it's funny, this harp player brought me his little VibroChamp once, it stopped working so the pros at Sam Ash sold him new tubes -- and when I say new tubes I mean 2x6V6S. Anyhow... in that case with 2x6V6S and no rectifier installed the amp didn't make sound at all.

    I wonder what the difference might be there. I didn't do any probing around, once I spotted the 6v6 in the rectifier socket I felt I understood the problem well enough! haha
     
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  4. sds1

    sds1 Tele-Afflicted

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    OMG JINX CORLISS YOU OWE ME A COKE
     
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  5. radiocaster

    radiocaster Poster Extraordinaire

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    That's assuming the amp was made for a 5Y3 or something. However, I'm guessing it was made for a 6X5.
    [​IMG]
    [​IMG] [​IMG]
     
  6. muscmp

    muscmp Tele-Afflicted

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    i can't find that the champ used anything but a 5y3 including its first incarnation as a champion 600.

    play music!
     
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  7. dougsta

    dougsta Tele-Meister

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    Maybe it was hit by lightning and now it's champion the super champ, test it with kryptonite :)
     
  8. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    He said "champ builder" so it could be anything, but I'd also expect a 5y3 in most instances.
     
  9. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The builder said it was supposed to be a 5Y3.

    I still can't figure out how the heater filament got hot.
     
    Last edited: Apr 17, 2021
  10. monkeybanana

    monkeybanana Tele-Holic

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    mmhmm
    Want to know something really stupid and embarrassing? I did the opposite.

    One late night in the dark I put a 5Y3 in the output tube socket. In my defense JJ tubes are the same size.

    The negative feedback resistor took the hit. Glad I had it on (I had a switch installed).

    Short vintage tubes from now on :)
     
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  11. D'tar

    D'tar Friend of Leo's

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    .
     
  12. Commodore 64

    Commodore 64 Friend of Leo's

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    This happened to me with a 68 Drip edge. I tell the story and nobody believes me!

    Until now?
     
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  13. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    I don't know about *working,* but I can cheer up those of you who've swapped a 5Y3 with a 6V6 by accident. Because I've done it twice. The first time I had an excuse of sorts, on a '55 GA-9 with tubes that looked like this. Yeah, you got it. First, the rectifier is on the right (Gibson, you crazy kid) and it also looks a lot like the 6V6 next to it, while the *other* 6V6 is a brown-base. The amp however didn't work with the 'wrong' tubes, as you can imagine.

    upload_2021-4-17_14-40-56.jpeg

    No excuse the second time. It was just your typical 6V6 and 5Y3 in the dark behind an 5F2a I was too lazy to turn around to see what I was doing. It didn't work either. I didn't try it with a 6V6 in both slots, though. Any volunteers out there???
     
  14. dan40

    dan40 Friend of Leo's

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    Did he have the safety diodes strapped across the rectifier socket? This may be the reason it worked.
     
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  15. robrob

    robrob Poster Extraordinaire Ad Free Member

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    I asked about the safety diodes with no answer yet but the tube would still have to conduct to get any output.
     
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  16. milocj

    milocj Friend of Leo's Ad Free Member

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    I don't know if this makes a difference or not, but I ran into an odd situation with the last 5F11 that I built. I had some larger transformers so I figured it wouldn't hurt anything to tie pins 1 and 8 (going by memory) together for a possible quick trial with EL34s.

    I also like to use the coin base 6V6GTs that were around in the early '70s because I've seen them take some crazy high missing without issue. I kept getting a buzz that would go away and come back as I swapped tubes and I ran across something on the net that mentioned certain eras of certain brand 6V6s used that additional pin for something else.

    I took out the additional tie to ground and the tubes that buzzed have been working fine. Any chance that could cause the additional conduction?
     
  17. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The only part that doesn't make sense to me is a second heater connection. One of the 5v heater lines is connected to the 6V6 heater pin 2 and the second 5v heater line is connected to the 6V6 cathode. I can't see how any heater current would flow unless the cathode and heater filaments were shorted together.
     
  18. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    If safety diodes were installed using pin7 as a *blank* terminal, the tube could conduct VAC across the heater of a 6V6. High voltage on pin7. Heater voltage on pin2. Both center taps connected. No telling what actually happened but that would be a scenario to provide heat.
     
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  19. gusfinley

    gusfinley Tele-Afflicted

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    I have tried 12AX7s as EL84s before which resulted in the cathode bias resistor getting smoked!
     
  20. robrob

    robrob Poster Extraordinaire Ad Free Member

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    I'm still not completely sure but I believe @radiocaster got it right. It seems the amp was built for a 6X5.
     
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