Yet another 5F1 Tweed Champ build (Tube Amp Doctor) - My first project

Discussion in 'Shock Brother's DIY Amps' started by perr0, May 12, 2020.

  1. perr0

    perr0 TDPRI Member

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    Hi, all,
    After 20 years (that's true, 20) considering building a vintage tube amp, I finally started with a Tweed Champ today.

    I bought it from TAD (Tube Amp Doctor, from Germany). Full kit, including cabinet and Jensen C8R speaker.

    I've attached some pictures of the parts as they arrived. Quality looks good overall. One of the cab inner corners looks like wasn't put together as well as the others.

    [​IMG]

    [​IMG]

    [​IMG]
    This inner corner doesn't look too good.

    [​IMG] Handle looks sturdy.

    [​IMG]

    [​IMG]

    [​IMG] Hi

    TAD's instructions are not as detailed as Stewmac's and Mojotone's, so I'm always referring back to these companies' documents as well.

    After my first day working on it, I have a few questions already. Would be great if anyone could help me out with some.

    1. Resistor 10k ohm in Stewmac's kit is metal oxide. It's carbon composite in TAD's. Is it a problem? What's the difference?
    2. Resistor 470 ohm in Stewmac's is carbon film. Again carbon composite in TAD's. Problem? What's the difference?
    3. Do I have to completely fill the eyelets on the board with solder? This picture show a half empty eyelet. Is it ok like this? I assumed it wasn't so already improved some.[​IMG]
    4. This is how my finished board is looking like. Doesn't look great, but hopefully good enough to work properly. [​IMG] [​IMG]
    5. TAD instructions asks for 2 holes to be drilled on chassis side next to transformer. They don't seem to exist in Stewmac's. Are they really needed? [​IMG]
    6. Stewmac's wire routing for eyelets 1 and 15 (green wrapped wires) and grounding bus layout are quite different from TAD's. Any advantages of one route over the other?[​IMG] [​IMG]
    Apologies for the very long post. I'm trying to learn as much as I can with this build so that I can try harder ones later (Bassman in mind).

    That's it for now. I'm sure I'll have other questions in the future. Thank you all in advance.
     
    Last edited: May 12, 2020
  2. guspac88

    guspac88 Tele-Meister

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    First order of business, in addition to filling the eyelet, it should look like there is "surface tension" on the surface of the solder: it should flow nicely to the edges of the eyelet and stick to the entire perimeter. Yours generally don't do this, which means you are heating the wires enough, but your iron isn't sufficiently heating the eyelet itself, so the solder isn't flowing onto it. Just reheat the joints, making sure the iron touches all the leads AND the eyelet.

    Second, I assume those green wires going through the board are your heaters (do they connect to the pilot light?). If so, they should be wrapped to reduce AC hum which would be caused by long parallel runs of wires containing AC voltage.

    As for the two holes in the chassis, I can't tell what is connected to the top one, but the bottom one contains your safety ground (connects the chassis to the ground of your home wiring) and ideally the safety ground is on its own terminal and screw. This doesn't have to be on the side of the chassis, it is often placed on the transformer lug nearest to the power cable's hole. Be sure to leave the safety ground wire longer than the other two so that if the cord is pulled loose, the power connections break before the ground. Other grounds positions are highly debated, but you should be able to get an idea of some acceptable places you could use by looking at a few 5f1 diagrams and pictures.
     
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  3. Telecentric

    Telecentric Tele-Meister

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    Agree with the above post. Those cold solder joints are going to be a problem. The good news is that those components can take the heat, so reflow all of them.

    It's hard to condense good solder technique into one picture, but this does a decent job

    soldering101.png
     
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  4. perr0

    perr0 TDPRI Member

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    Thank for the soldering tip. I'll try that.

    The green wires are for the filament heaters and pilot light. I just saw a comment on the layout asking them to be wrapped. There's clearly a differe t routing for these. Are there any advantages of one over the other? Stewmac's looks tidier to me as the wrapped green wires will be held in place by the board holes.

    Apologies, I didn't notice I had left it out of the screenshot. The top one is just holding a plastic clip for the power cord. I don't see anything similar on Stewmac's or Mojotones.
     
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  5. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    Welcome to TDPRI.
    Look up - Rob Robinette How amps work.
    Rob Rob is a TDPRI member and has amassed a great deal of information concerning several amps. The 5f1 is one of them.

    To have a successful build I suggest you follow his diagrams. The layouts are better than TAD, Stewmac, Mojotone etc.

    You should drill one hole for the power cord ground.

    The bias resistor (5W greenish color) gets very hot. Make sure the caps next to it have some room so they don't get overheated.
     
  6. perr0

    perr0 TDPRI Member

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    This is great, thank you. I watched a bunch of YouTube videos but had not seen any specific tips for the eyelets.
     
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  7. guspac88

    guspac88 Tele-Meister

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    If the power cord (ha, power chord!!) is firmly in place via the grommet on the chassis, don't worry about putting that internal clip in. If it feels loose, definitely try to snug it up somehow, but honestly I have never considered that solution.

    The heater wire routing is pretty open ended, I would run it where you think it looks nice. Twisting the heater wires tightly gives you a bit of room to place them in theoretically questionable spots (such as by the filter caps, as seen in the MojoTone picture), but if you hear a low pitched hum when your amp is on, you might consider pushing the green wires around with a chopstick till you find a place the hum goes away. This will usually be hugging the metal chassis or just placing them far from any signal carrying wire, especially in the preamp.
     
  8. guspac88

    guspac88 Tele-Meister

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    His layout and information are GREAT, but if you choose to follow them, make sure you understand what he is doing and why, or you'll mix up your layouts and end up with ground loops or miswired heaters, etc. I speak from experience, I missed a ground on my first 5f1 because I blindly followed one of Rob's layout but didn't realize my jacks weren't grounded to the chassis! Dumb mistake.
     
  9. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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  10. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    As guspac88 said, the heater wire can be routed as you like. Personally, I would not run them under the board.
    If the board would have to be removed:eek:, it would be a bigger pita.
    Some builders don't want any wires under the board because it is so difficult to lift/remove the board for repair or mods.
     
  11. perr0

    perr0 TDPRI Member

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    I've been reading his 'How amps work section. It's really good. Never though about using his diagrams -- I'll have a look. Thanks.

    I'll keep that in mind. I'm already worried about that by looking at TAD's and Stewmac's docs. Thanks.

    Great info, thanks for these.

    Good point. I already have some jumpers under the board. Will keep the heater wires exposed though. Thanks.
     
  12. tubegeek

    tubegeek Tele-Afflicted

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    +1 on improving your solder joints: many of the ones shown simply won't work properly.
     
  13. perr0

    perr0 TDPRI Member

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    I've re-soldered most of the eyelets. Looks a bit better now.

    This is how the chassis look at the moment. I'm now struggling to drill the side of the chassis, need to wait for the centre punch I just bought to arrive in the mail. I don't want to start assembling more parts and risk damaging them when drilling the chassis.

    [​IMG]

    Thank you all for the great help. I'm really impressed but how helpfull you all are.

    More progress updates and one more question:

    Which side of the chassis should this fuse holder "rubber washer" be?
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  14. BigDaddy23

    BigDaddy23 Tele-Holic

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    Getting there, mate!

    Can I suggest you reflow those eyelets? Most are not up to par and need a lot more solder. They will likely create issues for you when you go through the start up.
     
  15. perr0

    perr0 TDPRI Member

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    Do you mean like these?
    [​IMG]

    They look "half full" from this side because I actually soldered some eyelets from the other side.

    Question, should I solder both sides of each eyelet so that the solder fills the eyelets from both sides? I only applied solder from on of the sides (normally on the same side as the wire).
     
  16. tubegeek

    tubegeek Tele-Afflicted

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    The eyelets are not wetted. Those are melted metal, not solder joints.
     
  17. BigDaddy23

    BigDaddy23 Tele-Holic

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    @perr0 - it would be better to solder from the top, that way you can see the quality of the connections when looking in the amp. Way easier to troubleshoot too.

    Those 2 eyelets above look to be ‘cold joints.’ Go through and re-flow them all by simultaneously heating the eyelet and the leads with a wet tipped iron. Add a bit more solder to fill the eyelet completely, leave the tip in contact for a couple seconds, then remove it. It should look shiny and full. The whole task will take you 5mins.
     
  18. perr0

    perr0 TDPRI Member

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    I don't mind doing it, but this would be the third time I do this. Can I damage the components by heating them so much?

    Do you think they look like cold joints even knowing we're looking at them from the bottom (as they were soldered from the other side).
     
  19. BigDaddy23

    BigDaddy23 Tele-Holic

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    Not a problem if you heatsink the cap leads during the process.

    The other thing to do is to lay the wires to your sockets down against the chassis. You can then fly your heaters up in the air for good hum resistance.
     
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  20. Paul-T

    Paul-T Tele-Meister

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    croc.jpg Use a crocodile clip to protect the components, especially capacitors.

    The solder should be more obviously flowed onto the eyelets.
     
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