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New adventures in 5E3

Discussion in 'Shock Brother's DIY Amps' started by theprofessor, Jan 11, 2018.

  1. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    I moved a few things around today. Tonight, I'll ground the preamp and run through the schematic. Tomorrow evening I'll go through the startup process.

    I moved the earth ground from the power cord to the top right lug of the PT. Some folks don't like it there, because it can shake loose over time. I've got a jam nut on all the PT bolts, though--two keps nuts each--so I think it'll be fine! The B+ and CT will ground together to the chassis where you can see the phillips-head. And I also put in my zener-mounting station, as I'm convinced I'll need them to get to my target voltage of 350-360V. But first I'll fire it up without it and see where my voltages are.

    IMG_9952.JPG
    Since I moved things around, there's now an extra hole in the chassis that will be unused. The tag strip for the zeners is mounted up off the board on nylon nuts, since the eyelets are conductive
    IMG_9955.JPG
    Finished up the power wiring here, securing everything with internal toothed lock washers and blue lock-tite.
    IMG_9956.JPG
     
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  2. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    I like your zener tag strip, I plan on using that type or similar for a few things in my eventual build.

    There's another option available to you. You posted that your PT secondary dc resistance was around 109 ohms. The dcr of vintage PT's is, I believe, around 330 - 350 ohms or so. So if you wanted to duplicate the vintage PT's sag response, you could kill two birds and put a 200 ohm, 5w or 10w wirewound resistor in front of your first filter cap, and drop 15 - 20 volts that way, and at the same time mimic the sag characteristic (the PT source R) of the vintage PT's.
    Depends on what you want though. Of course, it could be that your B+ ends up right where you want it without any need for tweaking.
     
    Last edited: Jan 18, 2018
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  3. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Thanks, @RLee77 ! That's a great point. I may have a 200Ω Xicon wire-wound cement resistor, but it's possible that the lowest I have is 250Ω. Anyway, it gives me something to think over when I know better what my voltages are. I had not even considered the internal resistance of the high-voltage secondary wind as part of the performance (which of course it is!); I was only thinking in terms of volts.
     

  4. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Got the preamp ground bus wired up to all the grounds. Now to check everything against the schematic. Startup process sometime tomorrow.

    IMG_9959.JPG
     
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  5. SacDAve

    SacDAve Poster Extraordinaire Silver Supporter

    Age:
    66
    Dec 23, 2009
    Rocklin Ca.
    That dose look nice :) Will this be your first experience with a 5E3 ?
     

  6. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Thanks, @SacDAve ! Yes it is. I don't think I've ever even played one of any stripe before--original, clone, nothing. Only heard them on records. I'm excited!
     

  7. jsnwhite619

    jsnwhite619 Tele-Afflicted Ad Free Member

    Age:
    34
    Sep 10, 2013
    Georgia
    I was the same way. First one I was in the room with was the one I built. My wife probably wishes I still had never heard one! Haha

    Sent from my XT1585 using TDPRI mobile app
     

  8. SacDAve

    SacDAve Poster Extraordinaire Silver Supporter

    Age:
    66
    Dec 23, 2009
    Rocklin Ca.
    OK I was afraid of that. I would suggest giving notification to any neighbors within a ¼ mile radius of your home they will most likely be subjected to prolonged periods of extremely loud music for extended periods of time
     
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  9. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Love it! Done!
     

  10. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Here is my marked-up schematic. I think I'm good to go. One thing I found interesting was that it looks like the .02μF coupling cap couples the plate of 12AX7B (pin 1) to the grid of 12AX7A (pin 7). I'm sure @robrob remarks on this on his 5e3 page, but I didn't remember that. I actually don't see the .02μF value for that cap anywhere on the Fender schematic.

    5e3 schematic markup.jpg
     
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  11. JuneauMike

    JuneauMike Friend of Leo's

    May 5, 2015
    Alaska
    This has been a great thread for us newbies to read. You've put on a clinic on how to carefully and methodically go through your circuit to try to catch errors or omissions. I think I'll do the same annotations to my schematic before I power up my build, I see how it would be really valuable.

    Thanks Professor.
     
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  12. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Thanks, @JuneauMike ! I'm very happy if my build can be instructive and helpful for others. I'm basically a newbie, too, so everything is kind of thinking out loud. But it's really encouraging to know that this thread can serve as a resource for others who are making their way for the first time or whatever. Cheers!
     
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  13. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Well, shoot! I don't know what's going on. I went through the startup process, and the only thing that stuck out to me was that all heaters were reading 6.9V. But I think that happened on my last build. No light bulb flashes on the current limiter, no smoke, etc.

    Then when I play the guitar through it, it just sounds muffled and bad. With both volumes all the way up, it's not as loud as my 5f2a. The only cool thing is I'm picking up some cool radio when I'm taking the measurements on the pins. I am working directly under a light fixture over my dining room table, so...

    As I'm working very near the chassis, there seems to be a faint burning smell...

    Working from the "Typical 5e3 voltages" chart posted on @robrob 's site, here's what I've got. Some stuff is really high! I list the "typical voltages" first, then I give my voltages next.

    Filter capacitors
    B+1: 370V; mine: 382V
    B+2: 318V; mine: 355V
    B+3 247V; mine: 308V

    V4 6V6
    plate, pin 3: 362V; mine: 369V
    screen grid, pin 4: 317V; mine: 351V
    cathode, pin 8: 20V; mine 21.3V

    V3 6V6
    plate, pin 3: 362V; mine: 372V
    screen grid, pin 4: 317V; mine: 350V
    cathode, pin 8: 20V; mine: 21.3V

    V2 12AX7
    B plate, pin 1: 164V; mine: 202V
    B cathode, pin 3: 1.2V; mine: 1.62V
    A plate, pin 6: 200V; mine: 248V
    A grid, pin 7: 17V; mine: 16.3V
    A cathode, pin 8: 45V; mine: 57V

    V1 12AY7 (this is nuclear!)
    B plate, pin 1: 138V; mine: 298V
    B cathode, pin 3: 1.9V; mine: 9V
    A plate, pin 6: 135V; mine: 298V
    A cathode, pin 8: 1.9V; mine: 8.97V


    Fire away! Feel free to state things that should be obvious, because I might have missed them or not know them!
     

  14. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    You've got a missing or poor ground somewhere around the V1 cathode circuit, or a really wrong value for that cathode resistor. That tube is biased into cutoff right now.
     

  15. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Thank you. I'll look around.
     

  16. SacDAve

    SacDAve Poster Extraordinaire Silver Supporter

    Age:
    66
    Dec 23, 2009
    Rocklin Ca.
    Check your out put jack wireing
     

  17. The Guy

    The Guy Tele-Holic

    740
    Sep 15, 2016
    Guitarsphere
    I would also double check resistor values around b+1 and b+2 ...there is a weird voltage jump happening there
     
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  18. SacDAve

    SacDAve Poster Extraordinaire Silver Supporter

    Age:
    66
    Dec 23, 2009
    Rocklin Ca.
    Are the Jacks Swicthcraft? I think your good if they are
     

  19. SacDAve

    SacDAve Poster Extraordinaire Silver Supporter

    Age:
    66
    Dec 23, 2009
    Rocklin Ca.
    Hears the voltages of one of mine, I think your in the right range maybe a little high. Have you tried all the inputs? Scan 150550000.jpg
     

  20. The Guy

    The Guy Tele-Holic

    740
    Sep 15, 2016
    Guitarsphere
    Also what`s happening here? ...looks like there is a bridge between those two pins.


    amp tdpri.JPG
     
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