First scratch build 5E3

Discussion in 'Shock Brother's DIY Amps' started by anglinnr, Apr 19, 2019.

  1. anglinnr

    anglinnr TDPRI Member

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    1. Intro: (you can skip this)

      Please allow me to introduce myself, I a man with no wealth or taste. I’ve been around about 60 years now but my life’s not been a waste. Anyway, like stated I’ve been around a while and I haven’t been satisfied with staying in one place or at one thing. I don’t have much of a formal education, just high school and U.S. Navy Photographic Lab Tech training but I got a PHD in hard knocks. My approach to life has always been if ya ain’t been there then go and if ya ain’t done it then go do it. Never wish you had, although there are a few things that maybe I shouldn’t have. Na, No regrets. I am an expert on nothing but have a limited knowledge on may things and an opinion on most everything. In 1972 I worked for my uncle on a ranch in central Oregon and at the end of the summer he told me that he couldn’t afford to pay me but I could take home the motorcycle I had been using to get around the ranch on. That 1962 Bridgestone, much to my mother’s dismay, was the beginning of a lifelong love affair. The only thing I have stuck with longer than my wife of 32 years. Although I have gone through quite a few motorcycles over the years I have kept the same wife. I took some guitar lessons in my freshman year of high school but it got in the way of beer and other things so it didn’t last long. Oh that guitar borrowed from an uncle that I packed back and forth in the snow without a case, a 1959 ES-335. If I’ only know. I rediscovered the guitar at about 50 and like all things in my life you go all in or you give it up. Well still can’t play but it don’t stop me from bugging the locals with my noise. I started restoring old broken sticks I picked up here and there and then started building my own electrics. Now I’ve branched off into amps. I picked up an original non reissue Fender Blues Deluxe that had some fried circuits, no tubes and no chassis. Wasn’t even sure if it was all there but the price was good. $10. Now I have a pretty sweet sounding amp stuffed inside a 1946 Zenith radio cabinet. Now I think it is time to build from the ground up and that is what brings me here this forum.

      My Build: (this is the real stuff)

      I started out with the schematic for a Fender Deluxe 5E3 obtained from the ether world. I did some reading on a couple sites but mainly robrobinette… And I thank you for all the great info you put out there. As this is my first from the ground up build I wanted to keep it simple. Fat chance of that with my personality. Anyway thought it would be nice to have a distortion channel and a reverb and started reading and altering the schematic. As you can see I decided that maybe a reverb might be a bit much so I went with the FX Loop and will start working on a standalone reverb. I went on to add modifications I thought might be good ones to add, through everything in a box shook it up real good and dumped it out on the table. I had my granddaughter draw lines from part to part and came up with this. Now I submit for your consideration this fine work... or not work…

      PS: this is also my first forum so I apologize in advance for any errors in etiquette. And again I can’t than Mr. Robinette enough for the web site.
      PPS: I know that some feel it their duty to point out the dangers to life and limb but I am aware that the world will end if I put my body parts in the wrong place and I also know that the best way to discharge a large cap is to put my tongue across both leads. Thank you.
     

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  2. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Looks like an interesting amp.
     
  3. Cantbreak100guy

    Cantbreak100guy Tele-Meister

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    Pleased to meet you, hope you guess my name.
     
  4. anglinnr

    anglinnr TDPRI Member

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    What's troubling me is the nature of my gain. and FX loop:)
     
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  5. anglinnr

    anglinnr TDPRI Member

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    Thanks. And as stated earlier, I thank you very much for the information on your web site. Most of what I did here came from information from there and a compensation is due on payday. I hope my understanding of it was sufficient. I have on more than one occasion discovered that I did not understand as well as I thought I did.:rolleyes:I have been adequate in parts replacement and this might have been a little too ambitious for a first but I have a problem with stopping when I should. Instead of just changing out the 170 cu in 6 cylinder in a 70 Maverick i gatta stuff a bored and balanced 351W in it. "Never use a 2-way switch when a 3-way can offer a third option :D". anyway Thanks
     
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  6. flyswatter

    flyswatter Friend of Leo's

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    Starting with a 5E3 is a wise choice. The circuit is straightforward enough to teach you the ropes, and you'll get a nice useable amp that is portable enough with enough power for club gigs, jams, and band practice. Good luck.
     
  7. anglinnr

    anglinnr TDPRI Member

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    Grand daughter and I have been at it again. I cut out a bunch of shapes and gave her some colored pencils, had her paste them down and draw lines between them. She does love to color:). Seriously though I have spent some time going over this and made a few changes and am in desperate need of someone to check my work. Will I blow myself up if I do this? Any chance it might work? If you have suggestions as to some changes I might make before starting it would be appreciated. And by all means feel free to tell me I’m in over my head here. I fully understand that I am lacking in the proper education to engineer any electronics. It won’t stop me from trying but at least I will know where I’m falling short and need to study up a little more.
    As far as the layout goes I have a cabinet in mind so that is why the diminutions of the layout. There is some room for play in it and if it won’t fit I will find another cabinet, or build one. As for the use of the shielded cable, I have a few hundred feet of the stuff so I figured why not. Could probably find a way to use more in some places, unless it is going to cause an issue I am unaware of, in which case I could eliminate it all together as well. I have never used turrets before but it seems like a good way to keep things looking nice and air space for cooling under the components. Chose the transformers that looked to fit the bill. I have not purchased any components yet so my layout could go south do to size issues. I used DIYLC to create it and figured the parts in their toolbox would be close anyway. Took the dimensions off of the spec sheet for the transformers.
    Thanks in advance
     

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  8. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Looking good, anglinnr!

    Glancing at your schematic, it looks like you've got a center tap on the 6.3 V PT heater winding. If so, you don't need the pair of 100 ohm resistors to ground.
     
  9. anglinnr

    anglinnr TDPRI Member

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    R28 & R29? thanks I will eliminate them. and the ground too? I would assume this but like I said I am not an engineer.
     
  10. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Yes - R28 & R29.

    I see in an earlier version of this schematic, there was no CT on that winding. The latest one shows it, though. Did you change transformers, or original schematic was based on the Fender schematic (which had no CT), and now it's been updated for the PT you're actually using?
     
  11. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    However, I should add that many on this board advocate using the 100 ohm resistors to ground as the preferred method for creating the CT for that winding, because the resistors can serve as protection for the transformer if there is a tube failure which shorts the winding.

    Perhaps someone with more specific experience on that issue can weigh-in! I guess the point is you don't need both - one or the other!
     
    Last edited: May 6, 2019
  12. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    And it's also been suggested that if you have a CT on this winding, you can do a similar protection inserting a series resistor to ground. Merlin describies it here:

    http://www.valvewizard.co.uk/heater.html
     
  13. anglinnr

    anglinnr TDPRI Member

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    Thanks. Yes I based this on an original Fender schematic and then began my modifications. After looking around a bit I came up with the current transfers. I may cap off the CT and use the resistors if it has proven to be a a safer method but will follow the link and do a little more research. Appreciate the help .
     
  14. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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  15. anglinnr

    anglinnr TDPRI Member

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    Ok .if I follow right the center tap is to help reduce hum, the resistors are a safety feature in case of a short in the power valves. A better solution to what I have done would be to elemielim the false center tap and place a 100ohm resistor on the transformer center tap then to ground .
     
  16. Wyatt

    Wyatt Tele-Afflicted

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    Get rid of the artificial center tap entirely, strip it right out. You don't need it. We don't use both a real CT and an artificial CT, and since the PT has a dedicated CT ... use it. The CT (real or otherwise) is there as a ground reference for lower noise.

    Run the CT from the 6.3 secondary straight to pin 8 of V4. This will provide a DC elevated ground reference. Done. No reason to buy and install the 100R resistors ... less parts, less labor, less real estate. Don't overthink it.
     
    Last edited: May 6, 2019
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  17. anglinnr

    anglinnr TDPRI Member

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    Thanks. Major problem of mine. Over thinking things and over engineering
     
  18. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    That's not a problem - it's a virtue ;). What's the old slogan - "Inquiring minds want to know"?

    The great thing about this forum (of many) is that a question on one topic can bloom into something a bit unrelated, but always informative! In this case, it's doubtful you expected this to devolve into a discussion about heater supply biasing, but that's what it turned into! And there are so many experienced folks out there willing to chime-in - unbelievable (full disclosure - I'm not one of them - just starting out myself).

    The thing is - there's not always one answer to a given question - it sometimes depends on the context. If someone with an existing amp (and PT without heater supply CT) wants to address hum, the recommendation might be this virtual CT through 100 ohm resistors. In this case, you get the PT protection from shorted tube failure for "free".

    As @Wyatt points out, if you have a heater supply CT, there's no reason to create this virtual CT. I have no experience with whether there is merit to putting a current limiting resistor in the path to CT reference - have only read about it ;)

    Finally, there is what seems to be the most robust solution which @Wyatt mentions in his post - elevate the reference for the heater supply. You could do in either case - tie the virtual CT or actual CT to the power tube cathode in the 5E3.

    The goal of all of this, as I understand it, is to minimize the voltage difference between the heater filament and cathode to:
    1. Reduce induced electron flow which propagates through the downstream stages of the amplifier (hum).
    2. Stay as far away as possible from the max rating for heater-to-cathode voltage difference (tube life).
    First step is to switch from a single-ended heater supply to one with a center reference - this cuts the applied voltage difference from the heater supply in half. Due to biasing of the tubes (either cathode or fixed), there is additional DC elevation which can be applied to further reduce the difference between heater filament and cathode. In your case with the cathode bias of the 5E3, this can be picked up at V4 cathode. If fixed bias is applied at the output tubes, this doesn't work, and there is an alternative suggested here:

    https://robrobinette.com/Generic_Tube_Amp_Mods.htm#Heater_Elevation_Using_a_Voltage_Divider

    Good luck! Keep us posted!
     
  19. anglinnr

    anglinnr TDPRI Member

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    Thanks again. With an ageing mind as well as body new things are sometimes hard to grasp. No reason to stop trying, you just have to work harder at it. The more I learn about this the more I understand that I don't know or understand. I have worked with electricity most of my life (no I don't know much about that ether) and I thought that I would have a firm grasp on the movement of electrons through the circuit of an amplifier but the talk about elevating and biasing has my head spinning.:confused: Not to weary, I won't give up. Or maybe someone should:eek:
     
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  20. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Just remember - repetition leads to familiarity ;) Stick with this forum - it will grow on you. And the answers are here for the taking!
     
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