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Rookie Build: Champ 5F1

Discussion in 'Shock Brother's DIY Amps' started by TeleSlug, Jul 15, 2020.

  1. TeleSlug

    TeleSlug TDPRI Member Silver Supporter

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    Last week I asked for advice on next steps for my first build and got a ton of useful advice. Thanks!

    Prebuild Activities & Questions

    So far I've built myself a bulb limiter following Rob's plan. I also started on a tremolo pedal, which is coming along slowly but surely. I'll post a build thread for that over in the effects forum. I also ordered a cabinet for the Champ that will ship in early August.

    I'm about ready to order the Mojotone kit and plan to get these additional parts but have a couple questions:
    • Switchcraft 12A plug so I can eventually use the speaker with a different head, but is this the right one? Do I also need a male plug?
    • 25 uF, 25V capacitor as suggested by @Lowerleftcoast, but of course Mojotone is out of stock. Is there an alternative? Even if it's a pricier part it might be worth it to avoid extra shipping charges.
    I already have the stuff in my cart to build a capacitor discharge tool. I already have my tools and solder. Is there anything else I should go ahead and buy now?
     
  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Yes, male and female 1/4 inch. (Female has a switch (tang).)

    Capacitor: 10uF to 25uF... 25volt to 100volt will be fine. Radial caps are ok too.
     
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  3. tubegeek

    tubegeek Friend of Leo's

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    Neat!

    Here's a dirty little secret- which you seem to have a handle on - it's usually more important to consolidate your orders to the fewest vendors, than it is to get the best price, as a general rule.

    Honestly you can probably find 22uF/16V somewhere and that'd still be a safe voltage rating. 25uF/50V is just Fender's original value and it is not super-critical as mentioned above.

    And there's always that last part....

    You might be able to get some bits&pieces on ebay or amazon with free shipping, worth a look.
     
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  4. screefer

    screefer Tele-Holic Silver Supporter

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    Mojo told me, last week, they had lots of 25uf/50v in stock. They get 25/25 restock next month.
    Take your time re BOM and minimize those shipping costs!
     
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  5. King Fan

    King Fan Poster Extraordinaire

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    Yes, 25uF/50V are great. The 12A jack is the (female) standard for mono (TS) ¼" connectors, their '250' plug is vintage correct (black plastic) or their '184' (I think) has the metal cover.

    To consolidate shipping, wait until you review all the Mojo parts, compare their drawings to Rob's (his are better) and review your options. But don't get too fancy. Build stock, mod later.

    The guys are smart to say build slow. I recall that 'can't wait to try it' feeling, but.... You'll have the amp forever, the planning stage is totally fun, free, and safe, and building is fun too, safer if slow... and much more fun if it works when you start it up!!!
     
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  6. mjcyates

    mjcyates Tele-Meister

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  7. King Fan

    King Fan Poster Extraordinaire

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  8. BigDaddy23

    BigDaddy23 Tele-Holic

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    Wise words here.

    Re tools - a sharpened chopstick and a good pair of curved needle nose pliers are invaluable. It's also handy to have some extra turrets or eyelets in the kit in the event you do go down a modding path. They cost next to nothing and can be added to any component order.

    Welcome to the darkside!
     
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  9. andrewRneumann

    andrewRneumann Tele-Holic

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    I wish turrets cost next to nothing. Has anyone found turrets for cheap?
     
  10. Kevin Wolfe

    Kevin Wolfe Tele-Meister

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    IKR, even eyelets have more than doubled in price since I started building.
     
  11. screefer

    screefer Tele-Holic Silver Supporter

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    For comparison and if you want to go this route, I just received these...
    IMG_0858.JPG
    3" X 15" fiberboard...$3.19 each
    Brass eyelets...14 cents/each
    staking tool...$22...ouch!
    All prices Canadian
     
  12. TeleSlug

    TeleSlug TDPRI Member Silver Supporter

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    Okay, I think I am pretty well set. Thanks @tubegeek for the explanation on the voltage range @mjcyates for the link on the cap.

    I read up on Rob's mod for the speaker jack and added the right parts to my cart. I am going to build it pretty much stock to start. On my little pedal build I've been taking it slooooow. I'm learning that when I get the least bit irritated or impatient it's time to put the project away for the day. Also, swearing is a good indicator. ;) This is supposed to be fun, right?

    Yes on the chopsticks! Those are already in my toolbox and I am loving the long-nosed pliers I picked up. Thanks for the suggestion on the eyelets. I added those to the order and can do some practice with those.

    Ah yes, the darkside in the gentle glow of the tubes.
     
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  13. King Fan

    King Fan Poster Extraordinaire

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    I have a question for the smart folks following along here. On the Mojo layout, many of us would probably prefer to run the hot/black wire from the fuse out to the switch instead of the neutral/white. (Reason: basically, leaves slightly less amp 'hot' if the fuse fails.)

    But is there some way that running the neutral out there is quieter, given that the AC wires to the switch cross the signal wires to the pot? As I say, household AC is beyond my pay grade.

    upload_2020-7-17_9-16-39.jpeg
     
  14. andrewRneumann

    andrewRneumann Tele-Holic

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    At the risk of taking this thread off its rails...

    The neutral is the lesser of two evils? It has current (varying magnetic field) but it doesn’t have much voltage (a tiny varying electric field). I suppose it has the small benefit of providing some electrical shielding too.

    I could be wrong, but if I had the choice I would bring neither hot nor neutral mains wire near my signal wire.

    Ok throw darts.
     
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  15. TeleSlug

    TeleSlug TDPRI Member Silver Supporter

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    No worries from me (OP) on potential derailment. Just don't hit me with any darts.
     
  16. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    From my limited understanding, unfortunately no. *Neutral is not quiescent; it pulses at line frequency just like the hot.* In the illustration the switch is in the return path to neutral.

    The signal wires can be routed away from the AC but chances are the construction of the pot/switch is where most of the noise is picked up. The best solution is a dedicated switch.
     
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  17. King Fan

    King Fan Poster Extraordinaire

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    That's what I figured, but I wanted to make sure before I looked around for my 'in a perfect world we don't switch the neutral' soapbox... :)

    And I agree a separate switch is the answer, as in a 5F2a. But I don't want TeleSlug to freak out as we debate -- zillions of 5F1s have been built with the AC on the pot. As a technical point, running the black / hot from the fuse out to the switch and back is better; the neutral then goes straight to a PT primary. But thousands of amps have been built with switched neutral, too.
     
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  18. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I don't see why TeleSlug shouldn't freak out. Heck I am freakin' out trying to figure the number of amps with soldered turret boards adhering to NASA-STD-8739.3 [8.3.1], [13.6.2.a.5] standards passed the DOD QC inspection and have been launched into space! And further, are any of those amps in danger of being hit by some Tesla roadster on autopilot? Who's tracking this stuff? I bet the guys at whereisroadster.com don't have a clue these amps are out there. We all should be freakin'. There is too much stuff in space.

    OK. Back to Earth.

    The other day I was looking at the Bourns push/pull pot to see if it could handle the AC for this application. I did not find the rating for the switch, only a rating for the pot. It is a DPDT so both sides could be used, but I would think it might be a tad uncomfortable should the voltage find it's way to the push/pull knob. Then I thought "Hey the guys with VVR's don't seem to mind 400 volts at their fingertips".

    Naw, I don't think I'll try it... yet.
     
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  19. TeleSlug

    TeleSlug TDPRI Member Silver Supporter

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    Nope, not freaking out. I just finished a successful build of a tremolo pedal, so all happy thoughts here.

    My plan is to build the Champ pretty much as standard and then make any modifications. From what I understand, which is not yet a lot, many choices on wiring have to do with reducing noise. I also know the original designs were often based on cost and efficiency so I'm not surprised people have come up with new approaches.

    Oh, kit was ordered today. :)
     
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  20. TeleSlug

    TeleSlug TDPRI Member Silver Supporter

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    I'm back! The kit arrived on Thursday and this morning (Saturday) I followed Rob's advice on build order and started on the board. The first two pics are of just the components. The second two pics are with the jumpers and leads installed. The blue tape is my labeling of where the leads connect.

    Besides whether it looks correct, I have a few questions:
    1. Have I left enough of a gap between the fiberboard and the resistors to dissipate heat?
    2. Do the piggybacked caps (white ceramic and electrolytic) need space between them?
    3. When I get to soldering, how do I deal with the cloth-covered wire? Does it need to be trimmed back before soldering? Once leads are trimmed should I also trim up any fraying cloth?
    Thanks in advance!

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