First amp build...5F1 Boot Hill kit...can someone look for obvious goofs?

Discussion in 'Shock Brother's DIY Amps' started by Ashentep, Nov 19, 2019.

  1. Ashentep

    Ashentep TDPRI Member Ad Free Member

    Age:
    37
    Posts:
    71
    Joined:
    Mar 10, 2016
    Location:
    Va
    This is my first amp build and I’m a little gun shy as I recently had a golf cart battery blow a battery up, throwing acid all over me and damn near deafen me while doing some troubleshooting (turned out it had a bad battery...huh...go figure). That was 36V, a far cry from the voltages in tube amps, granted a much higher amp load. I’d feel better with someone just looking at these pics.

    I did as much testing as I could come up with on the multimeter, shy of plugging in and turning it on. I’ve got a light bulb current limiter as well, which I will use when the time comes.

    I do have effects pedal experience which helped a ton, and I’ll say, it’s a joy working with a chassis as “large” as the champ compared to a 1590B pedal case.

    Anyway...Any pointers would be appreciated. I tried to keep wiring away from each other as much as possible. I’m rambling, as I tend to do...here’s the pics:
     

    Attached Files:

  2. mabinogeon

    mabinogeon TDPRI Member Ad Free Member

    Posts:
    52
    Joined:
    Nov 16, 2019
    Location:
    Upper Michigan
    One quick observation I have is that in the photo that begins with 99BB, it appears as though the wires were pushed through the socket tabs and soldered in place.

    I think it's considered best-practice to bend and crimp the wires around the tabs to ensure a solid mechanical connection as well as a good solder connection. i.e., you want the joint to stay together without the help of solder and the solder is there to firm-up and secure the connection.

    You did a nice job tucking the heater wires into the corner of the chassis and routing them neatly around the tube sockets.
     
    Last edited: Nov 19, 2019
    Ashentep and King Fan like this.
  3. corliss1

    corliss1 Friend of Leo's

    Posts:
    3,489
    Joined:
    Sep 13, 2008
    Location:
    Lansing, MI
    And the thing I always mention on builds it seems - see if you can get more space between that large power resistor and the caps around it - both the power supply caps and the cathode bypass cap. The resistor gets hot enough where it can damage those parts if it's making contact.
     
    Ashentep and King Fan like this.
  4. Ashentep

    Ashentep TDPRI Member Ad Free Member

    Age:
    37
    Posts:
    71
    Joined:
    Mar 10, 2016
    Location:
    Va
    Thanks for the replies. I did indeed skimp on the rectifier socket mechanical connections. The other sockets I wrapped, that one I was in a rush and failed to wrap. I will go back and give it due diligence to avoid future failures.

    I had not thought about the resistors and heat buildup but that makes perfect sense. I will also make sure I change their layout to give them space.

    Again, thanks for taking the time to check it out.
     
    corliss1 and mabinogeon like this.
  5. Ashentep

    Ashentep TDPRI Member Ad Free Member

    Age:
    37
    Posts:
    71
    Joined:
    Mar 10, 2016
    Location:
    Va
    Also spotted a power tube pin I failed to wrap. Oops. It pays to pay attention and not get in a hurry I suppose.
     
    mabinogeon likes this.
  6. muchxs

    muchxs Doctor of Teleocity

    Posts:
    11,855
    Joined:
    Aug 14, 2004
    Location:
    New England
    Candy cane wire. Merry Christmas!

    Solder joints look good.

    I just stripped one of these to a bare chassis. Took me about 20 minutes. Most of the solder joints pulled apart without heat.



    Nit pickin': The signal return from the volume pot can be a source of hum in these amps. Keep it on the preamp side of the pot and / or use shielded wire. Ground the shield to the grounded lug of the pot.

    Shields only get grounded on one end.



    AC mains to the switch run over the pilot light. Pilot light gets hot. Run those leads under the pilot light tight to the chassis.

    Keep your wiring away from that bulb.



    Back to the candy cane wiring: Tuck the wires down between the board and the socket. They shouldn't double back over the board.

    ...although you kept the wiring as short as possible, generally a good idea. Just give the cathode and grid wire a poke away from the plate resistor.

    Your preamp triode sections are switched. Generally the guitar input feeds V1a. It's still wired "correctly" only with V1a functioning as the driver stage. That's part of the deal with the wiring flying over the socket.
     
    monkeybanana and Ashentep like this.
  7. Ashentep

    Ashentep TDPRI Member Ad Free Member

    Age:
    37
    Posts:
    71
    Joined:
    Mar 10, 2016
    Location:
    Va
    Thanks for the pointers. I will back over the socket wiring and pot wiring with your advice in mind.

    The candy cane wiring was in the kit. Might as well use it, right? Lol.
     
  8. Ashentep

    Ashentep TDPRI Member Ad Free Member

    Age:
    37
    Posts:
    71
    Joined:
    Mar 10, 2016
    Location:
    Va
    One more question. I did the startup sequence with the limiter in place and all readings were low, as expected. Amp sounddd funny with it in place...again...expected.

    Removed the limiter and voltage readings were considerably higher than the chart from boot hill.

    After calculating plate dissipation, it can in at just over 16watts. 16.04 by my math. My understanding is this is too high as the 6v6 has a max of 14watts...BUT the amp sounds great.

    So here is the question. I am going to experiment with bias resistors, but if making the bias colder removes the amp’s current mojo, what ill effects come from returning to this hot bias? I’ve done some searching but as most searches on the internet go, it’s both the worst idea ever and no big deal. I’m not sure what to believe here. I’ve also read where this is very common these days due to hotter line voltages.
     
  9. corliss1

    corliss1 Friend of Leo's

    Posts:
    3,489
    Joined:
    Sep 13, 2008
    Location:
    Lansing, MI
    Sounds about right. Is the tube redplating? If it's not redplating and it sounds good, you're all set.
     
    Junior Little likes this.
  10. Dreadnut

    Dreadnut Tele-Meister

    Age:
    65
    Posts:
    129
    Joined:
    Nov 4, 2019
    Location:
    Grand Rapids, Michigan
    Although the wires are pushed straight through the tabs and soldered, the solder joints look good so at this point I'd leave them alone, reheating and reworking them might just cause more problems.
     
  11. Ashentep

    Ashentep TDPRI Member Ad Free Member

    Age:
    37
    Posts:
    71
    Joined:
    Mar 10, 2016
    Location:
    Va
    No red plating issues that I can see, though the 6v6 is smoked so I’m not sure I would see it.

    Edit: meaning the glass is smoked...not as it went up in smoke.
     
    Mr Ridesglide likes this.
  12. bermuda

    bermuda TDPRI Member

    Posts:
    53
    Joined:
    May 15, 2017
    Location:
    Florida
    I agree - I've built 3 amps and never crimped with no issues.
     
  13. Ashentep

    Ashentep TDPRI Member Ad Free Member

    Age:
    37
    Posts:
    71
    Joined:
    Mar 10, 2016
    Location:
    Va
    Stick a fork in ‘er. Aside from a handle, it’s a done deal. The cab is 3/4”walnut, except for the baffle mounts being ~5/16” walnut. On the baffle I used what I had on hand...23/32” ply. I realize the thin baffle is part of the tweed’s persona, but I’m a frugal guy sometimes.

    Also went back in and added a NFB switch, which was worth its weight in gold, IMO.

    Thanks for the help and pointers!
     

    Attached Files:

    solfege and corliss1 like this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.