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Question for Bruce / Mission Amps regarding 5e3x2

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  • Question for Bruce / Mission Amps regarding 5e3x2

    I am building one of these not from a kit but using the weber tranny's and layout. I been reading everything on here I can about this and I noticed in an earlier post you replied...

    I didn't see the latest revision with the 15 watt 100 ohm resistor as a B+ dropping resistance.
    Looks they have made some changes.
    I wouldn't do that dropping resistor either.
    That unnecessarily uses up high voltage power tranny current doing no audio work.
    So what do you suggest as an alternative? I am planning on using a RCA 5u4gb for the rectifier.
    thanks for always being patient and helpful

  • #2
    Well, any B+ voltage drop before the OT is going to use up energy.
    Depending on the actual power transformer specs, I'd use two or three 10v 5 watt zener diodes in the PT's HI-V secondary center tap. Cathode band to ground.
    And, or, also try a NOS 5R4 rectifier tube instead of the 5U4GB.
    Not a 5AR4... a NOS 5R4. They are not that much money.
    If you are worried about the input capacitor value, use smaller value resistors (like 27 to 47 @ 2-3 watts or maybe 68 at 5 watts) before lugs 4 and 6 of the rectifier tube socket.
    Make sure your OT is rated to at least +30 watts and preferably in the 40-45 watt range. Those four 6V6s at idle will pull quite a bit if current through the OT.
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
    303-955-2412

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    • #3
      The Weber power trans come with 2 choices of voltages on the secondary coil. I just used the low voltage taps (red & white) on the PT along with a 5U4GB rectifier and the voltages were fine, 346 B+, 316 screen supply, 230 to the preamp & PI. No need for the 100ohm 25 watt dropping resistor.

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      • #4
        Originally posted by hasserl View Post
        The Weber power trans come with 2 choices of voltages on the secondary coil. I just used the low voltage taps (red & white) on the PT along with a 5U4GB rectifier and the voltages were fine, 346 B+, 316 screen supply, 230 to the preamp & PI. No need for the 100ohm 25 watt dropping resistor.
        Love that... they're still using a Chinese copy of my custom wound Heyboer MA798 PT.... The low voltage tap is indeed for the low power tweed 6L6 amps I build... and with a 5U4GB, should work fine for the 5E3X2.
        Bruce

        Mission Amps
        Denver, CO. 80022
        www.missionamps.com
        303-955-2412

        Comment


        • #5
          Thanks Guys very helpful as always!
          Hey Bruce, do you still sell your 5e3x2 xformers?

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