Mojo 5F11 Kit - Rookie Build

Discussion in 'Shock Brother's DIY Amps' started by GTG_Gopher, Feb 25, 2021.

  1. JuneauMike

    JuneauMike Poster Extraordinaire

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  2. GTG_Gopher

    GTG_Gopher Tele-Meister

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    When reading all of the strongly stated preferences, I try to take them in the spirit that they are given. Helps with the potential overload of info. I also realize that these preferences in all likelihood come from some sort of personal experiences. I think that these techniques and or materials give the users the confidence to do the job well. And that confidence leads to the person using them more, becoming more experienced and less likely to try other ways. So I don't think there's an intent of intimidation or gatekeeping, but an expression of what's worked well for them.

    For us beginners, I think it's important to strike a balance between getting as much input as reasonably possible but then start learning hands on asap and finding out what works for you and what your preferences are.

    And in the spirit of following my own advice, I started to pull the caps I had on there. They had been sitting there with their little seals broken for over a year, so it was probably already past the point of just being able to reseal them. Plus I also had already placed the order for the new ones.

    I also found in my stash of stuff another soldering iron with a chisel tip that i can practice with while waiting for the new tips for my soldering station iron. And yes, that made much quicker work of heating up the joints to reflow the solder.

    I also got to practice using the de-soldering wick and the solder sucker. Unfortunately the solder sucker I got started acting up. At first it worked fine, but then seemed to get clogged up and not wanting to reset. Is there a technique to keeping them clean?
     
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  3. The Ballzz

    The Ballzz Friend of Leo's

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    What solder sucker do you have? There are multiple brands and types. A pic might help us help you?
    Just Askin'?
    Gene
     
  4. GTG_Gopher

    GTG_Gopher Tele-Meister

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    Unbranded... 0168537c763da428f6176734471c46707f4561bf34.jpg
     
  5. Nickfl

    Nickfl Friend of Leo's

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    Sometimes they just get clogged and you have to take them apart and pull the solder out with needle nose pliers. I'm not sure there's any way around it, but maybe sometime will chime in with a good trick...

    I'm all for cheap, good enough tools, but last year I replaced my generic solder sucker with one of these: https://www.amazon.com/dp/B002MJMXD4/?tag=tdpri-20 and it was worth every penny.
     
  6. The Ballzz

    The Ballzz Friend of Leo's

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    Try unscrewing the tip end (be gentle) and dumping/cleaning it out! Try not to remove the grease that is likely in there! Some that look like that will actually allow the portion with the release button to be unscrewed from the metal tube! I've got the type below and while it's not nearly as small and "dainty" as yours, it is quick and easy to disassemble for dumping/cleaning. There are multiple brands of this style. Whatever you have/get, its important to have replacement tips available!

    Just My $.02,
    Gene
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  7. dan40

    dan40 Friend of Leo's

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    I use a set of welding tip cleaners to clean out the tips of my solder suckers. There are usually a couple of sizes in the set that are strong enough to push any stuck solder right through the tip and into the chamber. Then you just take it apart and dump it out. I tend to prefer the bulb type solder suckers though.
     
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  8. GTG_Gopher

    GTG_Gopher Tele-Meister

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    No, it's not particulary dainty, my workbench is a sewing table left behind by the ex. The scale on there is actually metric, the tool itself is about 8" long.

    The end does screw off, it's to the point now that after every use, i have to take the end off to clean it out. Right now the solder wick is working better for me.
     
  9. tubedood

    tubedood Tele-Holic

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    I have bent the legs of OD caps many a time, for years... and they are not leaking any DC voltage... maybe I got lucky? I wouldn't get too wrapped up in replacing them just yet.

    EDIT Ooops I see you are changing them.
    Practice makes perfect! (actually practice makes permanent if you practice bad form!)
     
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  10. J. Bonkosky

    J. Bonkosky Tele-Holic Gold Supporter

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    Lol! That was my first solder sucker. What I have done to keep them from clogging in the past was to coat the inside of the nozzle and barrel in a light coat of (silicone)dielectric grease. You can get this at the auto parts store cheep. It will be at the front counter in little sealed packets. Clean the sucker out with denatured alcohol then lightly coat the inside with the grease. The solder beads up and will be pushed out with the next stroke.
     
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  11. GTG_Gopher

    GTG_Gopher Tele-Meister

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    A bit of good news... The new tips for my soldering station arrived the other day, along a good sized roll of de-soldering wick. Also got some of the replacement capacitors, but three are backordered. :(

    So close yet so far...
     
  12. Greg70

    Greg70 Tele-Holic

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    I follow his facebook page and he has started selling some of his amp collection. He seems to keep his personal life under wraps pretty well. I hope he is still doing okay. He did another oil can video a little while back. Maybe he didn't cover the details as much because he had already covered it in the previous one?
     
  13. GTG_Gopher

    GTG_Gopher Tele-Meister

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    Well, a bit of good news. The final replacement cap has arrived! Grabbed a couple of it's buddies and had a little fun with macro lens here this afternoon. _MG_4132.jpg

    So hoping this weekend to do some soldering and get that board looking good!
     
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  14. GTG_Gopher

    GTG_Gopher Tele-Meister

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    Getting back to the amp here, I had to order parts. They came but at that point had some paralysis by analysis kicked in.

    Sadly right off the bat, I had another snafu along the way. I was reworking my high voltage wires from the Pt to the rectifier socket. In the process, I nicked the insulation on one of the rectifier heater wires with the soldering iron.

    How bad of a problem is this? I’m worried about how short this wire is getting, esp if I need to add onto it. Cut it way to short.

    Also got the hole drilled on the side of the chassis to move the mains ground off of the PT Bolt. Still need to do the one for the center tap and power amp ground.

    Next up after that is redoing the solder joints on the eyelet board. As part of that, I’m going to remove the green jumpers I had going underneath it for the preamp grounds. Sounds like it was not a good idea to have them running over eyelets on the back so I want to get those above the board.

    At the risk of opening up a can of worms, what’s the best way to do the preamp grounds? On the newer Mojotone wiring diagram they show the ground wires going from the board to the back of the pots and to one of the input jacks. Is this acceptable? I’d like to do a bus bar like on Rob’s schematics, what is a good way to build that, mechanically speaking?
     

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  15. wangdaning

    wangdaning Tele-Meister

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    Can you just put some heat shrink over the exposed area?
     
  16. JohnnyCrash

    JohnnyCrash Doctor of Teleocity Gold Supporter

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    I wouldn’t sweat it myself, personally. It looks like there’s some distance there.

    That said, I got major OCD these days. I’d consider stripping it back and resoldering… IF you have enough wire. Otherwise, for your possible OCD, maybe some shrink tubing.
     
  17. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    I may have said this already, but if Rob and Mojo differ, follow Rob's layout. I like Mojo kits a ton, but their layouts are not ideal in several areas. This is a prime example. The power wiring is another.

    A little poem: “If in doubt, use Rob's layout.”

    As far as *how* to build it, you can buy pre-tinned bus bar — nice — to isolate in front of the board, or strip a chunk of Romex core, but a few lengths of ordinary insulated wire routed to lie in front of the ungrounded eyelets will work fine and may be easiest on a first build.
     
  18. GTG_Gopher

    GTG_Gopher Tele-Meister

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    So please excuse the crude drawing. Looks like I had the right idea with the wires shown below but flubbed the execution. Wires should have been where the drawn line is? Not to scale of course... Back of Board 2_LI.jpg
     
  19. GTG_Gopher

    GTG_Gopher Tele-Meister

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    I ordered one of these here too and it showed up this week. Night and day difference how well it works compared to the cheapy one I had. I used it and some solder wick to clean out all the eyelets on the board save for the power amp ground bus.

    I was just going to do the preamp ground bus to move it out a bit, but got on a roll. I wasn't happy with how some of the components were sitting in the eyelets, with some leads crossing over each other rather than sitting side by side in the eyelet. Also got to clean up some stray leads taking up eyelet space from other rework attempts.

    Also gives me an opportunity to clean up the leads coming off the board. I wasn't using a sharp enough cutters on some and got a little mushroom of fibers on some ends.

    Got a few jumpers soldered back in, hopefully my technique is improving.

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