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  • 5e3 questions

    This is my first 5e3. I put one of these together on a test bed type rig because I plan to do some alterations to it.
    It's working quite well. Sounds great.
    What are the voltages suppose to be around the amp? I followed the fender schematic that doesn't list any. I found this on the web

    http://kilback.net/homebrewtweaks/am...ematic_r3v.gif

    I made a few changes on the input, I only put in one channel so one half of the 12AY7 is hooked up. That is pins 8, 7 and 6 are used only although I have both heaters running...mmm. Anyway this is what I have so far

    373v on the plates of the 6V6s
    342v on the screens
    38.9mA of idle current - I used the method of dividing voltages across the plate to CT of the OT by it's resistance.

    12AY7
    111v on the plate
    1.2v on the cathode
    These two are the ones I've been most concerned about.
    The other question is, the schematic calls for a 250ohm 5w cathode resistor. This seems to get pretty hot. I noticed that higher wattage ones are being used by others, is that the going approach for the 5e3?

    If you want, check out some pix
    Attached Files

  • #2
    I went with a 10-watter because I'm using 6L6WGBs instead of 6V6s
    Last edited by TD_Madden; 07-02-2009, 06:29 PM. Reason: correction

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    • #3
      I did a 5W 330ohm, because my 5E3 runs a little higher voltages (6V6s for me.) Works fine, though I never actually touch it (or anything inside the amp, for that matter) while it's on or before I make sure the voltages are bled off. Yikes! Been playing it for a year now, and when I do play once or twice a week it is played for at least three hours at a time, maybe four. No problems yet. I'd say 5W should be fine.
      In the future I invented time travel.

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      • #4
        What cathode resistor value do you have at 12AY pin 9, looks like 820ohms? You should have 1500ohms if only using 1 triode (voltage will rise if you do this). A 12AY normally returns about half the voltage applied to its plate resistor in a regular Fender circuit, so if you had 300vdc feeding the preamp plates, I'd expect to see a shade under 150vdc on the 12AY plate.

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        • #5
          Thanks for help, guys

          MWJB, that was an 820 ohm. Just changed it out with the 1500ohm and now the plate on the AY7 is is up to 133v and the cathode is 2.0v.
          Thanks again,
          pete

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