Blackface Twin Reverb Build (my first from scratch!)

Discussion in 'Shock Brother's DIY Amps' started by JKube, May 24, 2017.

  1. JKube

    JKube TDPRI Member

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    Hello good sirs! I'm diving head first into my first scratch build (I've done some board swapping and tweed cloning with some Valve Jr). I've decided to chronicle the build in some fashion here, since I know I will have a ton of questions anyway. I've scrubbed the forums and have found 100 5E3 builds, but no definitive front-to-back TR build. Thought that I might be able to fill that gap (with the help of some of the gurus on here). I've spent weeks committing Robrob's website to memory, and reading what seems like every AB763 thread in this forum (If anyone knows of a gospel thread that I missed, please direct me!) Either way, it's time to get this thing going. Wish me luck!
     
  2. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Subscribed.
     
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  3. JKube

    JKube TDPRI Member

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    Noone I'd rather have subscribed....
     
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  4. JKube

    JKube TDPRI Member

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    So I picked up some unused parts from a good friend. He had planned to build something, but never found the time. I inherited a chassis, transformers, choke, basically all the large parts. I also got a few bags of small parts sourced from Mouser, but couldn't make them match any spec sheet or schematic for a twin build. I was advised (on these forums) to stick with a single vendor's build, and build it to spec before starting to look at lead channel mods, etc. With that advice in mind, I ordered the small parts kit from Mojotone. The bags below were my Mouser parts. The two cases came from Mojo, along with eyelet boards for Filter caps, AB763, and rectifier board. That, plus a power cord and some green/yellow/black wire made up the bulk of the kit.

    View attachment 427852 IMG_8816.JPG IMG_8819.JPG IMG_8820.JPG

    I must admit, I'm impressed by the organization of the kit. The layout and schematic obviously leave something to be desired, but that's a complaint as old as time.....
     

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  5. Frontman

    Frontman Tele-Holic

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    I "blackfaced" my old TR recently, and had so much fun doing it that I decided do a complete rebuild from scratch. Looking forward to watching your progress.
     
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  6. JKube

    JKube TDPRI Member

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    I wanted to get a feel for the eyelet boards, so I went ahead and set up the Filter and Rectifier boards. The kit was "supposed" to come with 22uF 500V caps, but they subbed 20uF. I have some Sprague 25uF 500V's in the scrounge. My understanding is that this should "tighten" things up. Beyond tonal differences from value, would anyone suggest the Vishay/Sprague set over the Mojotone set? Any issue mixing these with the Mojos in the other stage?
    IMG_8821.JPG IMG_8823.JPG IMG_8824.JPG
     
  7. arielyitus

    arielyitus Tele-Meister

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    Nice! Do you gig? I can't really use my 5e3 nor my 18 watter that much because of them being too loud.
     
  8. JKube

    JKube TDPRI Member

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    I don't really. I have a DRRI that is my go-to, but I'm a fan of loud and clean! The Deluxe Reverb does that well enough, but I wouldn't mind having a high-power 6L6 rig. This one will be a head, been working on the cabinet for a while already. Excited to show you guys that, hopefully tomorrow! Tonight I just get to decrypt the little items on the AB763 layout that are eluding me.
     
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  9. clintj

    clintj Friend of Leo's

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    Following as well.

    The caps they sent are within tolerance for stock. The originals specified something like +/- 20%. I'd use the new ones they sent, they're pretty good quality (and brand new).

    The blackface amps are pretty complex for a vintage amp. Post plenty of pics as you go, nice and clear and well lit, and those following can double check your work. Test as much as you can before soldering parts in, too. I've had shenanigans like 330k resistors in the 3.3M spot in their parts kits before. Best of luck!
     
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  10. JKube

    JKube TDPRI Member

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    Appreciate it! I've been testing them on the bench, installing, then testing them in the circuit. I plan to to back and do a step-by-step retest when the whole board is done. So far I've found 3 caps missing from the kit. I had some 400V orange drops in those values, so I used those.

    I'm pretty comfortable with the offboard stuff (for now, I've never done heater wiring, so that will be fun) the biggest gap in instruction at this point, from what I can tell, is the back of the AB763. I know some people say to run everything on the topside, but it that realistic with everything this board has going on? I have yet to find a good visual, and the boxed letters on the layout are difficult to wrap my head around. Once I have all of the components in, The jumper and lead installation seems daunting. Any good rules of thumb for lead length as a starting point when populating the board?

    I got the board half-stuffed last night, before being pulled away to father. After checking out some pictures on here, I think I'll be pulling alot of resistors and leg-wrapping them on the caps. Was trying to make everything match the layout to a T, but resistor lead lengths and limited eyelet space are making that less of a possibility. Anyone notice any issues or better practices that could be executed in technique? IMG_8825.JPG IMG_8826.JPG
     
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  11. Outlaws

    Outlaws Tele-Meister

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    The best suggestion I can give for lead length is set the board in the chassis run the wire, then add a little length, cut, solder to the board, and then at the end do a final cut to length (if really needed) and solder to pots and sockets.
     
  12. jman72

    jman72 Tele-Afflicted

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    Good luck- I'm definitely going to watch this build closely!
     
  13. chemobrain

    chemobrain Friend of Leo's

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    I am impressed by your intentions.
    I don't even reach inside of amps, I am terrified of getting shocked all the way to the promised land.
     
  14. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Fender used the X and Y boxes to keep from cluttering up the layout. The wires run directly from point X to the other X.

    Separate all the cathode resistor/bypass cap pairs as much as possible. Try to elevate the resistors above the caps to help with heat dissipation.

    Do the "flying" heater wiring last.

    This silverface Bandmaster Reverb is almost identical to your layout. It has most wires run above the board.

    [​IMG]
     
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  15. Snfoilhat

    Snfoilhat Tele-Afflicted

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    All those wraps of small diameter reddish wire around the leads coming out of the doghouse: is that some kind of shield? Does it connect the brass plate to the board ground? Or only grounded in one place?
     
  16. Fiat_cc

    Fiat_cc Tele-Holic

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    It looks to happen in two different places too. Perhaps it actually connects the board to ground (as the brass plate is the ground bus in these amps yes?), and acts as some kind of shield too? I'm interested to find out.
     
  17. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The wrap does act as a shield and it does tie the circuit board ground to the brass plate chassis ground.
     
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  18. Pup Tentacle

    Pup Tentacle Tele-Holic

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    Shouldn't the plate resistors on v1, v2 and v4 be 1 watt?
     
  19. clintj

    clintj Friend of Leo's

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    All resistors are 1/2W with a couple of exceptions like the screen grid resistors and power supply dropping resistors. 1W is a common upgrade for those spots to reduce noise, however.
     
  20. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The silverface amps specify 1W for the plate resistors, but not the blackface AB763. It is a good upgrade though.
     
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