My collected stupid questions about a 5e3 build

Discussion in 'Shock Brother's DIY Amps' started by Jorgen83, Jun 7, 2019.

  1. Jorgen83

    Jorgen83 TDPRI Member

    Age:
    35
    Posts:
    24
    Joined:
    Jun 4, 2019
    Location:
    Netherlands
    My parts arrived, so here is my build thread in which I will collect all my stupid questions to you guys.

    I already filled the turret board (jesus those turrets don't like to flow do they? Will probably reflow some joints...):

    [​IMG]

    Here are my first stupid questions:
    - I don't want to use the standby switch. Instead I want to use to turn on/off NFB. It's an on/off though, but that should work right? Just add the resistor into the circuit and use the switch to turn it off?
    - Is it good practice to solder the eyelets on the reverse side of the board?
    - When doing the Rob Robinette master volume mod, I think the 1M resistor can be removed from the board, amirite? Or just leave it and connect the jumper to the other turret?

    I thought I had more stupid questions but that's it for now I guess. Will try to update on my progress, regardless of anyone wanting to see it.
     
  2. Uncle Daddy

    Uncle Daddy Tele-Holic

    Posts:
    780
    Joined:
    Sep 26, 2015
    Location:
    Maldon, England
    When using turrets, I wire through from the back and solder from the front. If you use the top holes for mounting the components there's little room for the wires, so I like to wrap the resistors round the turrets and just use the top hole for the caps. That way there's enough room for the wires. If you bend the top of the wires over a fraction, there's no danger of them dropping out, but to be sure I tack them to the reverse of the turrets.
     
  3. Jorgen83

    Jorgen83 TDPRI Member

    Age:
    35
    Posts:
    24
    Joined:
    Jun 4, 2019
    Location:
    Netherlands
    Well actually I was planning on wrapping the wires around the turrets... I think I might need to use some alcohol or something to clean off some residue because it was a bit of a pain for the solder to take. I already found one solder point which came loose from the turret after it had cooled.
     
  4. VintageSG

    VintageSG Friend of Leo's Ad Free Member

    Posts:
    2,931
    Joined:
    Mar 31, 2016
    Location:
    Yorkshire
    You need an iron with a hefty tip for turrets. There's a lot of heat shunt, and piddly tips lose heat too quickly. It ain't the wattage ( horsepower ), it's the torque ( mass ) that gets the job done providing the iron gets hot enough.

    A little additional flux can help too, and don't be tempted to use lead free solder. It's awful to work with. Heat the turret on one side until you're bored, then touch the solder to the other side. If the turret is hot enough, the solder will flow like a metal river toward the iron and you've now got a better surface for making the final joint. Allow it to cool before bending the component legs round though!, those darned metal tubes hold their heat for some time. You -could- ask me how I know, or you could work it out.

    Wire from the back. I 'tack' the wire in, then flow from the top/front when finalising. The solder flows to the wire, and all is good. Tacking allows the component to hold while you buzz things out to make damn certain you've got everything in the correct place. A highliter pen on the schematic/diagram when each path is verified, then add a black pen stroke when it's been given its final solder can save many frustrating hours of debugging.

    Resistors and ground paths get wrapped, as they're more or less non service items. Caps get inserted.

    Have fun, take your time, and enjoy the fruits of your labour as your glass glows and your amp springs forth with glorious life.
     
    awasson, flyswatter and Wally like this.
  5. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,472
    Joined:
    Dec 29, 2012
    Location:
    United States
    I would just delete the 1M resistor for the master volume mod.
     
    Jorgen83 likes this.
  6. D'tar

    D'tar Tele-Afflicted

    Posts:
    1,895
    Joined:
    Jan 11, 2013
    Location:
    WNY
    You may want to read through the NFB mod again

    https://robrobinette.com/5e3_Modifications.htm#Switched_Negative_Feedback

    From the link...

    "To determine the amount of NFB sounded best to me I inserted a 50k ohm linear pot between the speaker jack tip and V2A cathode for testing to vary the feedback resistance to find my sweet spot. I initially left the cathode resistor bypass capacitor in place but I soon realized it soaked up all the feedback. There was very little if any amplification or tone change with a sweep from approximately 22k to 50k."


    For the NFB to be effective you really need to separate the v2a cathode resistor and bypass cap. If you just want an on off you could simply switch the bypass in and out on v2a. The nfb is a good mod tho. this is how I've done a couple. On the second, you can replace the dp3t switch with a pot in series with the lowest value resistor as well.

    upload_2019-6-7_8-28-34.png

    upload_2019-6-7_8-35-20.png
     
    King Fan and Jorgen83 like this.
  7. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Posts:
    6,725
    Joined:
    Dec 23, 2009
    Location:
    Rocklin Ca.
    I've come across turrets that won't solider for whatever reason, I just remove them and install new ones. I've had two batches that wouldn't solder for anything I just toss and get more.
     
    awasson and Jorgen83 like this.
  8. Jorgen83

    Jorgen83 TDPRI Member

    Age:
    35
    Posts:
    24
    Joined:
    Jun 4, 2019
    Location:
    Netherlands
    I missed that part about the cap, thanks! Thing is I’d like to use the standby button and would need to get an appropriate switch that looks the same. It’s pretty easy to replace the switch later anyway so I’ll see how it works with this one first.
     
  9. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,472
    Joined:
    Dec 29, 2012
    Location:
    United States
    It won't work with an on-off switch. The bypass cap will "eat" the NFB.
     
    Jorgen83 likes this.
  10. dan40

    dan40 Tele-Afflicted Silver Supporter

    Posts:
    1,140
    Joined:
    Aug 19, 2015
    Location:
    Richmond Va
    As VintageSG mentioned above, you really need a larger tip for turrets. A decent soldering station also help. I use a medium size chisel tip in my Hakko 888 station when doing turrets. Also be sure to melt lots of fresh solder into your tip just before touching it to the turret. You almost want a small blob of melted solder hanging from the tip as you touch it to the turret. This helps to quickly and efficiently transfer the heat into the turret. A little dab of paste flux or a flux pen also helps out. The whole process should only take about five seconds to complete. If you need to leave your iron on the turret longer, you may want to use heatsink clips on the components to avoid heat damage.

    Many folks run their b+ jumpers under the board like the originals did but I have gotten in the practice of running all jumpers above board as you see in Marshall amps. This makes later troubleshooting and servicing much easier because you won't need to unsolder everything to lift the board.
     
    Jorgen83 likes this.
  11. Jorgen83

    Jorgen83 TDPRI Member

    Age:
    35
    Posts:
    24
    Joined:
    Jun 4, 2019
    Location:
    Netherlands
    Another stupid question:

    I have desoldered the 1.5k from the turret to do the NFB mod, but now it's hanging loose as I don't have a spare turret. What is the best approach to avoid shorting the lead to surrounding parts? I can shrinkwrap it after soldering it to the wire that goes to the switch...
     
  12. dan40

    dan40 Tele-Afflicted Silver Supporter

    Posts:
    1,140
    Joined:
    Aug 19, 2015
    Location:
    Richmond Va
    robrob and Jorgen83 like this.
  13. Jorgen83

    Jorgen83 TDPRI Member

    Age:
    35
    Posts:
    24
    Joined:
    Jun 4, 2019
    Location:
    Netherlands
    Next!

    I forgot to get a 1 watt resistor for the NFB mod, thinking I had one anyway but I only stock 1/4 watt resistors. Is that ok?
     
  14. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,472
    Joined:
    Dec 29, 2012
    Location:
    United States
    Yes, 1/4 watt is fine for NFB.
     
    Jorgen83 likes 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.