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How much current can a Deluxe Reverb OT really stand?

Discussion in 'Glowing Bottle Tube Amp Forum' started by NTC, Nov 25, 2020.

  1. Nov 25, 2020 #1
    NTC

    NTC Tele-Meister

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    About the best thing I have to go by is the 20W rating given by Hammond, though this is not a Hammond OT. I don't know it's origin - I got it 20 years ago.

    My "5F11" has this OT, which I presume is 6600 ohms to 8 ohms. The PT in this amp is about 380 - 0 - 380 vac and I am getting about 420 vdc on the 6v6's when biased. I am currently using a 5Y3 rectifier. This PT seems to be for a 6L6 amp. I am wondering if I could put some 6L6's in with, say, a 5AR4 and a suitably rated speaker. It would be too loud, of course. I just worry the OT couldn't takebthe current, though some people put 6L6's in DR's.
     
  2. Nov 25, 2020 #2
    jhundt

    jhundt Doctor of Teleocity

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    Just try it. I ran 6L6s in a PRII which has the same OT as a Deluxe Reverb. It worked fine. The power transformer did get pretty hot. But the OT never showed any signs of distress.
     
  3. Nov 25, 2020 #3
    NTC

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    I just went through rebiasing the amp again - I think I did something wrong the other day- so far I have 460 V on 6V6 plates and it still has one tube above 80% dissipation. Also, the to 6V6's are not well matched, but neither are the two halves of the ot about 75 ohms and 85 ohms.
     
  4. Nov 25, 2020 #4
    Viejo

    Viejo Tele-Afflicted Silver Supporter

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    Ohms readings on an OT are not really important. Turns are what matters. I wouldn't worry the OT has mismatched ohm readings.
     
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  5. Nov 25, 2020 #5
    Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    So long as you can hold your hand on the OT it will be OK.
     
  6. Nov 25, 2020 #6
    Dacious

    Dacious Poster Extraordinaire

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    Yes, the 80s Superchamp like mine uses the DR output transformer. It's a pretty conservative 20 watts IMO.

    Robrob's mini JCM800 build can use it with EL34s and they're getting up there for voltage. 5F11, no problem.
     
  7. Nov 25, 2020 #7
    NTC

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    The reason I mentioned the resistance was that I measured resistance for the plate dissipation calculation. I will give this a shot. Now I have to decide 6L6WGB or 6L6GC.
     
  8. Nov 25, 2020 #8
    Dacious

    Dacious Poster Extraordinaire

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    My JCM800 has 31ohm one way, 35 the other. When measuring low ohmages your meter isn't that accurate. You're also measuring coils not resistors. As Viejo said, they don't wind evenly. Same turns will inevitably amount to slightly more wire on one side.

    If you get radically different dissipation on the two tubes, try swapping. On my Marshall that produced an even ~1ma difference in calculated draw. There was no discernable difference in tone or output.
     
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  9. Nov 25, 2020 #9
    marshman

    marshman Poster Extraordinaire Silver Supporter

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    Well, 6L6s require about 2x the heater current, can your PT do that?
     
  10. Nov 25, 2020 #10
    NTC

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    This PT is a mystery, but given the output voltages and the fact there are only two preamp tubes, it should. I can't imagine a PT with this high of a voltage is meant for 6V6's.
     
  11. Nov 25, 2020 #11
    secretsoundz

    secretsoundz TDPRI Member

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    The JJ Electronic 6V6S's can handle up to 500 plate volts. They sound great too.
     
  12. Nov 25, 2020 #12
    ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Are there any markings on either transformer? I'm curious. :)

    FWIW, I'm using a Deluxe Reverb OT in a cathode-biased 2x6L6 amp, and it's happy as a clam running about 50mA through each side at idle. Probably not putting out more than ~20 watts in my case, though.
     
    Last edited: Nov 25, 2020
  13. Nov 25, 2020 #13
    schmee

    schmee Doctor of Teleocity

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    My BFDR ran 460 volts with factory PT. I tried 6L6's in it but with a 6L6 matched OT. To me it became much more sterile, I guess that is 6L6 vs 6V6 really. I pulled V1 and ran a SS plug in rectifier to ease the load a bit. Although I ran a tube rectifier for a while too. Eventually I went back.
     
  14. Nov 25, 2020 #14
    NTC

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    What rectifier was in that DR? I have 460v with a 5y3.

    No marking on the pt - if there was, it has been painted over. I would have to pull the chassis to look at the OT.
     
  15. Nov 25, 2020 #15
    printer2

    printer2 Poster Extraordinaire

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    The one winding is wound on top of the other, that is why the difference in resistance. the same number of turns but longer distance to go. On the transformers, if you can keep your hands on them I would not worry.
     
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