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5F1 Build Check

Discussion in 'Shock Brother's DIY Amps' started by JuneauMike, Oct 10, 2017.

  1. JuneauMike

    JuneauMike Poster Extraordinaire

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    Thanks jsnwhite, its worth my time to recheck all my soldering joints. I'll give those a second look.

    But my soldering has been generally very good on this build (can't say that on the previous build). And you are right, I try to use just enough solder to get the job done.

    But I will test the continuity on each side of the solder joint to make sure. I did this without fail on the turret board because it was easy to do. And did it on most all the other soldering joints, but I'm sure I missed a few. I think its probably a good habit to not get too confident in my soldering and verify even the stuff that looks shiny and secure.

    Here's a link to some really good info on soldering if you want to learn more.

    http://www.tdpri.com/threads/soldering-instruction.781928/
     
  2. tubeswell

    tubeswell Friend of Leo's

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    You can't necessarily tell from observation or resistance measurement. If one (or both) resistor leads have a faulty connection to the resistive compound in the resistor, it might look okay and even possibly measure okay, but still make noise
     
  3. JuneauMike

    JuneauMike Poster Extraordinaire

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    Observation (before, during and after the soldering) will tell you a lot about the physical connection and any resistance should lead you to suspect a bad connection. Neither is a perfect test but they are what we've got.
     
  4. tubeswell

    tubeswell Friend of Leo's

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    I'm talking about faulty plate resistors. You can't always tell by looking at them.
     
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  5. JuneauMike

    JuneauMike Poster Extraordinaire

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    Dude, you are a lifesaver. That's got It!!!
    I hotwired the amp and 85 percent of the floor noise went away. Took the volume switch out, rewired another in its place and it's still quiet. I've got to put my ear up to the speaker to hear the idle hum now. I'm happy with this. I'll bask in the glow and beer tonight and button it up tomorrow night after work.

    Thank you everyone, especially for tubeswell for patiently suffering a fool. You guys really taught me a lot.
     
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  6. FenderLover

    FenderLover Poster Extraordinaire

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    Congrats on getting it going.
    Like I said, I don't like AC switches on pots for that reason. I've drilled a hole on the back side for the fuse location in the corner opposite the power cord, and used the old fuse hole for a separate switch mounting location. That physically separates the AC from the audio, like it probably should be. And how often do you really need front panel access to the fuse?
     
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  7. JuneauMike

    JuneauMike Poster Extraordinaire

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    Amen to that. Looking back, its a dumb design and you would think would be more expensive than buying switches and volume wipers in bulk back in the day. But this was my first 5F1 so I really wanted to get as close to the actual design as possible without incorporating vintage speakers and vintage voltages.

    So if I can lean on you guys for just a little bit more to close the book on this:

    My symptoms were low to moderate 60hz buzz (or hum, I frankly can't always tell the difference) that appeared when the volume was at 4 and increased until about 10:30 to just before 11. At 12 it dropped off dramatically. So essentially as the signal strength grows so does the buzz, when the signal is wide open it disappears.

    Again, inputs, output and volume are isolated. No grounding combination that was tried affected the buzz (split ground, single point star ground, removing isolation washers, etc) When I short the ground lug to the volume casing the buzz/hum goes away.

    Was there anything here that should have led me to the volume wiper first? Is there anything I could have done short of hot-wiring the switch (that was genius, btw) that could have led me to that?

    An early diagnosis was possibly heater buzz, but that would have been more constant in a a SE amp since they are pushing right from the start. Right? This buzz was attenuated by the volume signal.
     
  8. FenderLover

    FenderLover Poster Extraordinaire

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    The buzz grew with the volume because the wiper is going to the input of the second gain stage. Finding that problem is not much different than finding any other bad component. It's more difficult tracking down a bad component that it is to find a mistake. When you mentioned grounding the pot case after i suggested moving the AC away from the pot, I was pretty sure you found it. When you take the 'anything is possible' approach, you start to doubt everything, so it's easier to start simple, and that's where experience comes in. Not that I'm a freakin' genius, we can get lucky too. ;)
     
  9. JuneauMike

    JuneauMike Poster Extraordinaire

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    Thanks. Ok, so the grounding to the pot casing was an important clue.
     
  10. tubeswell

    tubeswell Friend of Leo's

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    Grounding the pot casing should actually shield the pot from the AC Mains flux density in the SPST switch
     
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  11. JuneauMike

    JuneauMike Poster Extraordinaire

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    Ok, got it all back together and no power. Hmm. Chased down everything i could think of, took wiring off from the switch, hot-wired it and no power. About an hour or so of troubleshooting and I found that the current limiter was set to "maximum protection."

    Tried it again with the current limiter actually plugged in to the power strip this time and, what do you know, the amp fired right up. Pro tip: whenever feasible, use electricity to power your amp. (Dumb, dumb, dumb).

    The hum was back, but only at about 50 percent of the previous level. So I took Tubeswell's advice and grounded the volume to the pot. It is quiet as a mouse now. Perfect.

    Thanks again for everything.
     
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  12. robrob

    robrob Poster Extraordinaire Ad Free Member

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    I got a good chuckle out of this. Congrats on building and debugging a really nice little amp.
     
  13. JuneauMike

    JuneauMike Poster Extraordinaire

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    Ok, this is the final build posting. Really happy with this amp and I have to say it has exceeded my expectations. Sounds way bigger than it is. I'm really grateful for all the help I got on this forum and especially Robrob's site, which really gave me a more deep understanding of this circuit and how it works. I think I did this project right because I spent a lot of time reading, researching, planning and building fixtures and other things to assist with the build. In fact, I spent way more time preparing for this amp than I did in building it.

    Here's the finished product.
    champ_front.gif cub_back.gif guts.gif

    And here was a few things that I used in making this.
    This is the circle cutter jig I used for the baffle. It started life as a large cutting board. It mounts to the router base and I use a drill bit for a center pin. The whole thing just turns on the axis and you get a perfect circle. Took about an hour to build.
    circle.gif
    box-front.gif


    This was my router sled that I used to make finger joints. It started life as a 4x4 post, pressboard, scraps from a cutting board and a scrap of oak as a key guide. I spent an afternoon getting it to cut well, then it was off to the races. I've built two cabs with this so far.
    sled.gif
    box.gif


    This turret spike was just a couple of 3/8 bolts with nuts and washers. A little time on the grinder and it was good to go. Used a scrap of wood for the base.
    turret_spike.gif

    One of our hardware stores receives pallets of freight are protected by these 4x4 pieces of 1/4 inch pressboard. They just give the pressboard away for free to whoever asks for it. This stuff cuts and machines easily and makes nice template material or used as sacrificial material. Maybe your hardware store does the same thing.
    templates.gif

    But I have to say that one of the most important purchases for this build was my soldering station. It's not the worst, and not the best. But the adjustable temperature setting made soldering a joy and the digital temp readout gave me a bit more confidence that I was going to get a good joint. My old Weber pencil soldering wand used to occasionally take a break and cool down without telling me, causing me to screw up a solder. This thing ran great, and always gave me the temperature I was asking for. I used the big chisel tip on this and generally ran temps between 720 and 850F and got in and out as quickly as the joint would let me. And I used heat sinks liberally. The lamp top flipped up so you could look through the magnifying lens and see what you were soldering. Very nice.

    Thanks again everyone. Now, on to the next one.

    Happy Thanksgiving all.
     
    Last edited: Nov 22, 2017
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  14. jsnwhite619

    jsnwhite619 Friend of Leo's

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    I got that same soldering kit a few years ago except more expensive, and something died after like 20 hours of use. They wouldn't replace or repair, and I had to buy a new iron to replace the element in it - the irony of having to solder replacement parts on a soldering iron.

    I got a Weller 40 watt adjustable on Amazon and trashed the X-tronic and haven't looked back. The Weller has done everything I've needed so far.

    But congratulations on the build. I put a Jensen C8R in my Champ and I couldn't believe how much bass it had. Plug an iPod or mp3 player into it and you'll have the best sounding docking station you've ever heard.
     
  15. JuneauMike

    JuneauMike Poster Extraordinaire

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    Yeah, that price is about what I paid for it. If they wanted over $100 for an off-brand soldering station I wouldn't have gambled on it. It was a great deal at the time in that it came with extra tips, a lamp and a spare heating element.

    As it is, I'll use it till it doesn't work anymore and then just buy something else.

    Jensen, huh? Wow. I never hear anything good about those speakers for some reason. I'll have to take a second look at em.
     
    Last edited: Nov 22, 2017
  16. bigtuna61

    bigtuna61 TDPRI Member

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    Hey, beautiful woodworking, I just ordered a boothill 5f1 last Fri, will be making a cab for a 5f1 head. I have used a dado blade but seems to be a bit of tearout on the fingers, i think i would like to get a router setup for fingerjoints. But anyway nice work.
     
  17. jimgchord

    jimgchord Tele-Afflicted

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    Dado is more efficient and there are steps you can take to minimize that tearout
     
  18. bigtuna61

    bigtuna61 TDPRI Member

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    20180402_184959.jpg 20180402_184921.jpg
     
  19. JuneauMike

    JuneauMike Poster Extraordinaire

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    If you are going to cover the amp than I'd spread some Durham's Rock Hard Putty on the corners and then sand flush. If are building another one, I'd try to make your depth of cut a little greater so that the fingers are proud of the cabinet surface. Then you just sand them flush. Whether you use a router or a dado blade (whichever you are most comfortable with) you should use a thin sacrificial piece on the backside of the cut to minimize tear out. I've got a bunch of cheap 1/4 press board that's good for that.
     
  20. intensely calm

    intensely calm Tele-Meister

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    @JuneauMike, I am at the "ready to solder" phase of my 5F1 project, and I have a question for you.

    From your experience, what would be the most important takeaway(s) from your 5F1 build?
    I'm looking for suggestions such as "the importance of ground bus bars vs. (fill in the blank)", or other things that probably seem obvious now (after the amp is all together), but maybe not at the time you were building it.

    Any suggestions are welcome. Thanks!
     
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