6g3 build with pics

Discussion in 'Shock Brother's DIY Amps' started by trippercaster, Feb 9, 2019.

  1. trippercaster

    trippercaster Tele-Meister

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    Working on my third build this week and I have a few questions for anyone who has built a 6g3:
    • Should I add power tube screen resistors?
    • How about power tube grid stoppers?
    • I added a standby switch because I had another on hand, good idea or waste of parts?
    • The 290BX has 330/330 HV. Given ~122v wall voltage and the higher voltage from the PT, am I going to need zeners to drop voltage? I wanted to add ta SS rectifier switch but I'm sure the voltage will be way too high.
    • Please someone check my adjustable bias. I only had a 10K bias pot, but I think that's what is in the Down Brownie. Their first resistor appears to be 100K so I did that and I used 22K on the pot. Not sure if this will get the range of adjustment where I need it.
    I'm far from having a full understanding of amp theory. I'm more of a paint-by-numbers guy. Here's a few pics, I'll post more soon. It's a mashup of the Down Brownie and the mojotone/weber kits. Primarily used the Mojotone layout but stuck the filter caps on the board. Mainly because I didn't want to build a doghouse and I can make my chassis as long as I want. I added Rob's lead channel mod, switched NFB, multi tap OT. I'll probably add a MV when I decide which one to use.

    I realized on Thursday that I don't have enough jacks and I only have linear taper 1M pots. I ordered them but they won't get here until Tuesday. Unfortunately I have to head to Atlanta for the week so I won't get to finish until next weekend. I'll get as far as I can today though. Only a few more things I can do without those items.

    20190117_221956.jpg 20190209_113724.jpg 20190209_113733.jpg 20190209_113919.jpg 20190209_113742.jpg 20190209_113839.jpg 20190209_114048.jpg 20190209_114015.jpg
     
  2. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Cool amp. My .02:

    • Yes
    • Yes
    • Waste (see Merlin)
    • If you try a tube rectifier, I'd see the B+ before you decide
    • Cool, I'll be interested. Merlin also has a good page on bias where he shows how to calculate the bias circuit.
     
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  3. CoyotesGator

    CoyotesGator Tele-Holic

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    Oh Yeah!

    The 6G3 is a killer circuit.

    Love my clone I built a few years ago.
     
  4. trippercaster

    trippercaster Tele-Meister

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    @King Fan Thanks for the replies and the links. Definitely need to go back through those pages again. I think I'll understand it better now that I've a couple builds under my belt. I am a little worried about the grid stoppers changing the overdrive as Rob mentions on his 5F6a mods page. Might try it first without and then add them to hear the change. Not sure I really want to "modernize" the tone of this amp. I tried the 5.6K on my 5F6a and didn't like them at all. Went down to 1.5K and they were tolerable so I left them in.

    Also, all of the layouts I have show the grid leaks going straight to pin 5 without grid stoppers. Rob's 5e3 mods page shows grid leaks on pin 6 with the resistor between 5 and 6. Does that also translate to the 6g3?
     
  5. trippercaster

    trippercaster Tele-Meister

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    Oh yeah, I'm super excited to hear this in person. Based on what I've heard through headphones I think this will be my new #1. Love my 5e3, but need a bit more volume to hang with my drummer. Fixed bias and the LTP should do just the trick. I finished this over the holiday to pair with it:
    IMG_20190101_195305_382.jpg

    One piece double bound mahogany body. Homemade p90's wound just a little hot on bookmatched maple bobbins. This thing has balls.
     
  6. flyswatter

    flyswatter Friend of Leo's

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    Nice work so far. Here's my 6G3 build from last month:
    http://www.tdpri.com/threads/my-6g3-brown-deluxe-build.913632/

    As for your questions:
    - I did not add screen or grid resistors -- just went with the original schematic. No problems with the amp and no complaints from the buyer so far. I did at one point alligator the resistors in as part of some troubleshooting I was doing, but found no difference as far as sound or output.

    - Standby is a good idea, if not strictly necessary. If you are using a replica backplate, you can add it where the ground switch hole traditionally was. Otherwise, beside the power switch, blackface-style, is fine.
    - I also used Hammond 290BX and a GZ34 rectifier. No problems with voltages; no zeners necessary, in my case.
    - I forewent the bias pot (again, adhering to the original layout) but I do believe 10k to 22k is fine, since you can compensate when you adjust it.

    A couple of other points, based on my own build experience:

    If you power up and hear a massive ground loop hum, detach the ground for the preamp (4th) filter cap and run that one ground to the preamp ground. That cured the hum in mine. Every layout I've seen and the original 6G3 schematic suggest daisy chaining the FC grounds the way you have done. But I found out the hard way the problem it causes, as it took me hours to isolate the problem.

    If you're doing the traditional bias trem, it may tick in one or both channels. An easy fix for this if you don't want to dismantle the circuit is to add a trem on/off switch using a mini-toggle either on the front or (if the faceplate is already done) on the back beside the trem footswitch jack. Basically, the mini toggle does the same function as the footswitch itself (either will kill the click when Off) but the switch is convenient for the times you want the trem off (which is probably most times) and don't have or want a footswitch on hand.

    Cheers and best of luck finishing up.
     
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  7. trippercaster

    trippercaster Tele-Meister

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    @flyswatter What a beautiful build and a fantastic sounding amp. You seem like you know what you're doing, so I really see no reason not to follow the same grounding scheme. Very happy to hear your voltage was normal with the 290BX.

    Parts just got here from Tubedepot. Amazed how quickly they arrived. I want to get to startup tonight, but my 3 year old has puked twice since lunch and he has a metabolic disorder, so we may be headed to the ER instead...
     
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  8. thunderbyrd

    thunderbyrd Poster Extraordinaire Silver Supporter

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    gorgeous guitar!
     
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  9. King Fan

    King Fan Friend of Leo's Ad Free Member

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  10. flyswatter

    flyswatter Friend of Leo's

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    Thanks, King Fan!
     
  11. trippercaster

    trippercaster Tele-Meister

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  12. trippercaster

    trippercaster Tele-Meister

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    So it works. Took a while because we've all been sick as hell. Discovered several mistakes. Left out a wire and totally screwed up the bias circuit. I will provide more details soon, but I'm on the road the next few days.

    I don't think the recording does it justice. Sounds amazing in person. Best distortion I've ever had in an amp. No pedals or external effects used. I just made that recording in my freezing cold shop and cold hands make for sloppy playing. There's a little cleaner tones after 1:00 and 3:00 with tremolo. First few minutes are on the bright channel and the last minute or so is on the lead channel. I used the guitar pictured in my earlier post.
     
  13. John How

    John How Tele-Meister

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    She sounds awesome, tremolo works just right and when your digging in there she screams...betcha can’t wait to take to the next jam or gig...too bad your on the road for a while...unless your a travelling musician takin her with you...great build...I just got the chassis for mine from my metal working son so I’m doing some pre build planning in my old head and on paper...thanks for showing your build and giving us a sound check!
    Almost forgot to ask, what speakers are you running? I’m gonna try a couple of 10” alnico webbers in mine that I’ve had lying around...
     
  14. trippercaster

    trippercaster Tele-Meister

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    Thanks John! I really enjoyed your last build too. I was on the fence between the 6g3 and the 6g2. Really bummed I can't spend more time with it. I'll be thinking about it the entire trip. I was playing through a WGS G12 C/S. Absolutely my favorite speaker lately. I use the 10" version as well. I have a cab with one of each, the 10" is open back and the 12" is closed. That cab should make this amp loud enough to hang with my drummer.

    Sent from my SM-G960U using Tapatalk
     
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  15. trippercaster

    trippercaster Tele-Meister

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    A few pics of the finished product. [​IMG][​IMG][​IMG][​IMG][​IMG][​IMG][​IMG][​IMG]

    Sent from my SM-G960U using Tapatalk
     
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  16. trippercaster

    trippercaster Tele-Meister

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    The wiring got progressively more sloppy as I worked. In my defense, I was sick and so tired I was delirious

    Sent from my SM-G960U using Tapatalk
     
  17. CoyotesGator

    CoyotesGator Tele-Holic

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    Looks nice and sounds freaking fantastic!

    Don't know how you feel about G12-65's or their clones but it is a match made in heaven IMHO.
     
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  18. flyswatter

    flyswatter Friend of Leo's

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    Congrats on getting the build done. So, no grounding or trem issues... that's good to hear. Don't beat yourself up about the wiring. You've got the heaters twisted and elevated and grounding scheme wired in a way that should produce a quiet circuit. I personally find that the first time building a particular model is more about getting the thing to work properly. Pretty lead dress and all that can come on the next build, when you are more sure things are going to work and you can concentrate on the finer details.
     
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  19. trippercaster

    trippercaster Tele-Meister

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    Thanks Man! I love them, just not the price. I also have a WGS Invader like flyswatter used, I believe that will be closer to a G12-65. Planning to try it when I get home. If it sounds notably different I'll post another clip and invite people to choose a favorite.


    Oh I had issues with the bias/trem. Just haven't gone into detail on what I screwed up. Tubes red-plated at first. I realized the first resistor in the circuit was sized for tapping the rectifier tube, not the same when using a dedicated 50v tap. To get the bias right, I have the 10k pot nearly completely off, so I want to adjust the resistor values to get it set closer to the middle of the range I need.

    I do have a little more hum than I should. Might be worse in the shop due to fluorescent lighting, laptop power supply, etc., but I still need to hunt down the source and fix it.

    My voltage was high for some reason so I tried a 5U4 and that helped. I will post my voltages when I get back home.

    I struggle with lead dress. Mainly because I had only used stranded PVC coated wire, which doesn't want to stay where you need it. This is the first amp I've used the cloth covered solid wire and I will NEVER go back. So much easier. If this were my third amp using that wire I know I'd have a cleaner build. I actually ran out at the end and had to use a few strands of the old stuff, a big contributor to the sloppy appearance.
     
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  20. kleydejong

    kleydejong Tele-Holic

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    Great looking and sounding build!
     
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