First Amp Build 5E3

Discussion in 'Shock Brother's DIY Amps' started by Dylan Bob, Jan 27, 2019.

  1. King Fan

    King Fan Friend of Leo's Ad Free Member

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    It'd be gratuitous to say I agree with Rob, a supernova of 5e3 knowledge, but FWIW the 12a125a (with the a) gets the nod more often than any other speaker if you read 100s of posts about this topic, and also it's the speaker Ted said was best for the 5e3. CJ at Weber still says that.
     
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  2. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    So, I've been strapped for time and haven't posted my updates. They have seemed to be too little each day to post anything, but now I'm at the point of checking my bias. I got through Rob's Amp Startup (It's amazing to have this resource. Thank you so much Rob). After some initial, "Why is it silent" anxiety I found one poorly soldered capacitor and a missing ground. Now the amp is too quiet through the 2 bright channels, but loud as heck in the 2 normal channels, which I equate with working properly.

    Can anyone think, offhand without seeing any photos of my build just yet, why this might be happening? I can hear a little guitar when using the bright channels with volume 2 fully turned up and volume 1 down. If I turn volume 1 (volume 1 being the pot in between tone and volume 2) then it gets even quieter. I cannot take pictures yet, but I will soon. I would appreciate any sure knowledge as well as speculation.
     
  3. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    I would like to post my bias readings because I read on Rob's Tube Bias Calculator (Thanks again Rob. You just keep giving) that my cathode biased amp is safe at 100% of max dissipation. I'm not sure whether my 123.4% result is in the unsafe region or deep in the safe region. Here are my readings in case anyone is bored. ;^)

    V3 Power Tube pin 3 DC V = 363
    V4 Power Tube pin 3 DC V = 363
    Output trans V at center tap= 372
    Center tap voltage(372) minus
    plate voltage (363) equals voltage drop (9)

    V3 Power Tube pin 3 Ohm = 209
    V4 Power Tube pin 3 Ohm = 209

    9/209 = 0.0430622 plate current in amps (43.06
    milliamps)

    Plate to Cathode Voltage for 6V6GT 12W
    V3 = 343
    V4 = 344

    Tube Dissipation Using Plate Current
    Plate Dissipation = 14.8 watts (for V4)
    Plate Dissipation = 123.4% (for V4)​
     
  4. 82LesPaul

    82LesPaul TDPRI Member

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    If you go to the Mojotone website for their 5E3 Tweed Deluxe Kit they have an excellent schematic, layout and build manual in .pdf about 1/3 of the way down the page. Excellent resource to help with build. I just completed one of their kits and between the aforementioned, this forum and Rob's website you can't go wrong.

    https://www.mojotone.com/kits/TweedAmpKits_x/Tweed-Deluxe-Amp-Kit
     
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  5. King Fan

    King Fan Friend of Leo's Ad Free Member

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    I take it you're using the "Measure Bias With the Output Transformer Resistance Method?"
    For the 5e3 I like to check my results and find this simplest: "Measure the Bias by Cathode Resistor Voltage Drop."

    But let's assume you have 14.8w. Play your amp in a dark room with the back panel off. Any sign of redplating? If you're running JJ power tubes, you'll be OK even at 14-15 watts. If you're using NOS (12w spec) tubes they may also survive -- but it's an expensive way of testing if they don't. :)

    Also waiting for our smart friends to see your pics (with well-lit details of input jacks, V1 socket, and the pots, I think) to see why your 'bright' channel is super-quiet. Obviously it seems like it has to be something local to the input / EQ sectors.
     
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  6. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    I was measuring with the Output Transformer Resistance. I measured with the Cathode Resistor Voltage Drop, just now, and got a plate dissipation of 120%. So, this is a little closer to the target. I was told the power tubes are NOS. They say DELCO, Made in USA, and the box one of them was sent in says Delco Black Smoke Tung Sol. I'll turn out the lights and watch the tubes melt, I mean watch for red plating as soon as it is dark. ;) Thanks for the feedback.
     
  7. robrob

    robrob Poster Extraordinaire Ad Free Member

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    I looked back and couldn't find them, do you have voltage readings for V1?
     
  8. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    I've taken voltage readings many times, but apparently I have a hard time posting them. Here are today's readings:

    V1 Pin 1 = 120.2 V
    V1 Pin 3 = 2.02 V
    V1 Pin 6 = 121.6 V
    V1 Pin 8 = 2.01 V

    V2 Pin 1 = 165.6 V
    V2 Pin 3 = 1.17 V
    V2 Pin 6 = 197.5 V
    V2 Pin 8 = 49.2 V

    V3 Pin 3 = 364 V
    V3 Pin 4 = 331 V
    V3 Pin 8 = 20.8 V

    V4 Pin 3 = 363 V
    V4 Pin 4 = 330 V
    V4 Pin 8 = 20.9 V

    B+1 Cap = 373 V
    B+2 Cap = 332 V
    B+3 Cap = 244 V​
     
  9. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Your voltages look good for the bright channel. The problem has to be between the bright input jacks and where the channels meet at the tone/volume controls. Verify all your component values such as the 1M on the input jack, 68k grid leaks, coupling cap and bright volume pot wiring and pot value. From the voltages the cathode resistor and plate resistor are correct.

    Also you could have a weak triode so try a different tube.
     
  10. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    I've seen this plan and it is mostly good. I don't like this method of attaching the fascia boards; when Fender did it, they tied to the top AND sides with fascia boards. @jsnwhite619 had a thread here somewhere where he took apart an original Deluxe cab. I notched my sides for the fascia but Fender glued and nailed them to the top and sides, then filled in remainder with, like, 1/4" x 3/4" strips. Again, see that thread by @jsnwhite619 .
    I don't like "hinging" the fascia (the attachment point for your speaker) to the top and bottom, only. Others mileage may vary.;)
     
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  11. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    Thanks for posting this. As fate would have it, I was going to attach the fascia today! I’ve been having a hard time finding info about how to attach it other than the way the plans above show, and I was concerned about hanging my speaker and baffle from only 3/8" of wood glued on the top and bottom. You may have helped me prevent making a big mistake. Phew! Just in the nick of time.
     
    Last edited: Mar 17, 2019
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  12. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Here is the thread from the first one, and I actually just wrapped another cab done the same way. If this topic had come up a few days ago I could have taken some better pics! http://www.tdpri.com/threads/tweed-fascia-cab-build-latex-floor-adhesive.884937/

    After seeing the original cab with 4 fascia pieces and trying it that way, it is WAY easier and faster. The top & bottom cleats go the whole width of the cabinet - a 20" wide cabinet would get 20" long fascia boards on top & bottom. Then the filler strips go between them. As far as durability of that way vs cutting into the boards and setting them in the notch, I've tried to pry & break apart enough pieces that I don't worry about it at all. Titebond really is like a weld -- I've seen chunks of wood tear out because the glue joint wouldn't break.
     
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  13. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    Glad I could be of some assistance to you. :)
     
  14. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    If I did it over again (big "IF"), I think I'd go this route. While not what a "joiner" would do, it makes for very fast production work and since it's typically covered it tweed, well..
     
  15. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Yeah, for a covered cab, no problem. My finished wood cabs like in my avatar pic has the cleats set inside the edge & glued on the ends and the long contact side, but I'm using full thickness pieces of wood for that. So, that's a 3/4" wide gluing surface. I wouldn't do it that way with a 1/4" or 3/8" piece, but for the 3/4" and glued on the ends - all clamped & glued - it would take a he11 of a hit to break it free.
     
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  16. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    ...and frankly, those are REALLY nice cabs!
     
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  17. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    I wanted to build my cabinet with solid pine, but it seems to be extremely hard to find pine boards ten inches wide. I didn't want to join pine boards for my first build, and I had a pretty nice looking sheet of baltic birch plywood. Here is a my box with four sides and a cutout for the amp chassis.

    box.jpeg
     
  18. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    My dad has some kind of plastic ... machine he got for making finger joints. We used it on this cabinet, and I think the joints turned out really well. Here is a photo of the joints glued together without any sanding.

    fingerJoints.jpeg
     
    Last edited: Mar 18, 2019
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  19. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    If I ever make another cabinet I think I will go the route of having the fascia boards go all the way across the front of the cabinet, but that was going to get dicey with my box-in-progress because I would have routed a lot of wood including the vary narrow finger joints on the top board. I watched a video in one of your posts about someone who had was rebuilding an old tweed cab and saw that Fender had the fascia boards kind of sitting in a route of the sides and top and bottom boards replete with finishing nails. So, I decided to try something like that. Here is a routed section I am chiseling the corners out of.

    chisel.jpeg
     
    Last edited: Mar 18, 2019
  20. Dylan Bob

    Dylan Bob TDPRI Member Silver Supporter

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    The fascia boards fit!

    fasciaFitting.jpeg
     
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