5E3 Build Advice

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by mabinogeon, Dec 4, 2018.

  1. mabinogeon

    mabinogeon Silver Supporting Member

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    Hello everyone,

    I recently started assembling a Weber 5E3 kit, but I am going to be out of town for a few days so I thought I'd post some pics here in case anyone was available to critique my work thus far while I am gone.

    This is my first amp kit, and really my first serious soldering project, so any feedback would be greatly appreciated. I bought the kit when Weber was having a 15% off sale, which is how I was able to afford it! I will be pretty upset if I fry a transformer or something and have to start buying replacement parts...

    Here's a long shot of the whole chassis:
    I wrapped the fuse socket with electrical tape because it felt pretty flimsy.
    I also ordered a nicer pilot light socket, as the plastic one that came with the kit pretty much fell apart.
    The red/yellow wire from the PT got a ring terminal to attach to the power amp ground, but I am planning to connect the green/yellow wire to the tube side of the power tube cathode resistor in an attempt to reduce the potential for hum.
    The Standby switch is attached to the chassis, but I am planning to omit it and brought the red wire from the OT right to pin 8 of V5.
    The resistors that go from pin 4 to pin 1 on V4 and V3 are screen resistors and after I run the filament wires, I will run a jumper between pins 1. I believe this is how Fender builds "The Edge" Deluxe model.

    I did drill a hole in the side of the chassis to add a dedicated mains ground. Hope that isn't a problem:

    Here are some close-ups of the sockets:

    Here are the pots thus far:

    @Jeff Gehring mentioned in a previous thread that he isn't a fan of the wire that Weber sends with the kits. The only other wire I have at home currently is 20GA stranded Teflon coated. Can I use the stranded in place of the solid that Weber sent? I assume the solid holds its shape and stays in place better.

    Other slight changes I plan to make are:
    Add a phase inverter grid stopper resistor.
    Change the first filter cap to 33µF and add a bleeder resistor to it.
    Lower the PI .1µF coupling caps to .022µF.
    I am not planning to use the brass plate for grounding. I plan to follow the grounding scheme on Rob Robinette's website.

    And just for fun, here's my basement work bench:

    Thanks in advance for any input/assistance/coaching!
     
  2. Bandit127

    Bandit127 Member

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    Congratulations on your first build. A 5E3 is a great starting point.

    Since you are asking for critique I will make the following suggestions.

    You solder joints generally don't look right. There is not much wetting between the solder and the components and not much flow going on. I think you might have an iron too cold for your solder temperature or maybe you are too worried about overheating stuff (don't worry about that on a valve amp). For me, the basics of a good joint are a sequence of events.
    1. A small amount of solder is added to the iron tip. This picks up flux (from cored solder but you obviously aren't using separate flux) and it gives you extra contact area to transfer the heat from the iron.
    2. The molten solder on the iron is pushed against the components. They will begin to heat if you have good contact. The iron is held in place long enough for the components to reach the melting point of the solder or near enough. This is almost instant for a resistor on a valve tab and a few seconds for a turret connection. When hot enough the solder on the iron will start to flow.
    3. With the iron still in place solder from the reel is fed in to the joint until sufficient solder flows through the joint to make it secure. If you pull the solder on the reel away from the joint at the start of this and it grabs or sticks then the components are still too cold.
    4. Pull the solder and iron away from the joint. Don't blow on it, wait for it to cool naturally.

    Try reflowing a couple of your wire joints. If you start to melt insulation then add 5 to 10 mm between the insulation and the joint. You do look a bit close on that score.
    This video gives some good tips and shows appropriate insulation clearance.


    Your next build needs more slack left in the wires. Leave a spare inch or two on transformer tails and wire runs because you WILL need to cut back and reconnect a wire or three during testing and in the life of the amp.

    Other than that you have a good looking, tidy build. Well done.
     
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  3. mabinogeon

    mabinogeon Silver Supporting Member

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    Hadn't thought of that, nor did they mention it in the kit instructions. Great idea though, especially with future repairs in mind.

    Thanks for your input on the soldering. Very helpful video, too. I have a 40w pencil iron and am using Kester 63/37 rosin core .031" solder. Before I go any further on the amp, I will practice with some wire and old components.

    One thing I didn't mention above was that I haven't properly soldered the resistor on the sockets. I lightly tacked them in place with just a dab of solder before I mounted the sockets to the chassis. Probably not the best idea, but I thought it would be easier to attach them outside of the chassis.

    I need to come up with a fan system to draw fumes away from the work area. This solder seems to smoke a lot, which makes it difficult to see the joint.

    Thanks again for your input.
     
  4. Tron Pesto

    Tron Pesto Member

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    You can go ahead and set up the fan, but none solder fooomes hav eavh hurted anyones headbrain in the head many at awl never. I bin breetheen s0ddah fumms fer dekaids end I'm am jusk foine!

    And it's like a canary mule NOS pleez!
     
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  5. Jeff Gehring

    Jeff Gehring Silver Supporting Member

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    A tech I used to work with a long time ago was NEVER without a short length of solder in the corner of his mouth, like it was a toothpick. He was kind of a nut then, and I don't imagine the lead ingestion helped out much!
     
  6. Tron Pesto

    Tron Pesto Member

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    And to be serious for a moment, theoretically, there is no lead in the fumes. The temperature to sublimate lead to a gas is way higher than soldering temperature. The fumes are basically the flux.

    Now, can breathing a lot of flux be a problem? Mebbe, and it's too late for me at this point.
     
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  7. VaughnC

    VaughnC Supporting Member

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    Yup, looks like you need practice soldering but that comes with time.

    Just remember, when possible, a good mechanical connection before soldering. Solder should stabilize the connection, not make the connection.

    Do the tube filament wiring as early as possible as it's tricky enough with nothing else in the way.

    And, when it comes time to apply power to the amp, be aware there's lethal voltage in a tube amp. A high voltage circuit really isn't the place for novice skills...so be very careful and respect the 120 to 500 volts in there. Good luck and be very careful.
     
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  8. pdf64

    pdf64 Member

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    It would be a good idea to build a light bulb limiter alongside the amp, such that it’s in place to protect the first power up.
     
  9. jthomas666

    jthomas666 Member

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    So... you're of Welsh extraction (as am I) and/or a scholar of medieval European lit?
     
  10. mabinogeon

    mabinogeon Silver Supporting Member

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    In a way, yes. According to those new DNA tests, I am 39% from "England, Wales & Northwestern Europe."

    "Scholar" is a bit generous, but I do have a degree in History and an interest in that time period in that part of the world. Nothing I've been able to make a career out of, though! I started using "mabinogeon" as a handle online maybe 20 years ago. The only place I've ever seen it spelled like that is in an old Bullfinch's mythology compendium. Everywhere else is "Mabinogion."

    I recall your avatar from the Ted Weber forums, where you recently answered a question I asked about their copper cap rectifiers.
     
  11. jthomas666

    jthomas666 Member

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    I hope my answer was accurate and helpful. Last PM I listened to a podcast from the BBC ("In Our Time") about the Mabinogion (https://www.bbc.co.uk/programmes/b0b1p5k7). Thus, my question. I lived in Lansing in the early 80's for a couple of years and traveled around in the UP (Copper Harbor) a couple of times. I liked it up there and that experience led me to find a similar place to settle down (Maine).
     
  12. Rockinrob86

    Rockinrob86 Supporting Member

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    With practice you can time your breathing to the soldering. Inhale, start the joint, hold breath, finish joint, exhale, breathe in from the side. No fumes!
     
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  13. Jeff Gehring

    Jeff Gehring Silver Supporting Member

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    I learned everything I know about soldering from this guy:

    [​IMG]
     
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