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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

New (and first) build: 5f2a Tweed Princeton

Discussion in 'Shock Brother's DIY Amps' started by theprofessor, Nov 2, 2017.

  1. tubeswell

    tubeswell Friend of Leo's

    Jul 1, 2008
    NZ

  2. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Thanks for the encouragement, RLee. I really appreciate it.
     

  3. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    tubeswell likes this.

  4. tubeswell

    tubeswell Friend of Leo's

    Jul 1, 2008
    NZ
    You mean the 'PT primaries'. ;-)

    I use insulated screw terminals. Neat, tidy and secure. Get a block and whack some terminals of the end with a Stanley knife. These ones have handy holes between the pairs of terminal blocks, so if you lop-off 2 pairs of terminals, you can use the hole for a mounting bolt attached to the chassis.

    [​IMG]
     

    Attached Files:

    Last edited: Nov 13, 2017

  5. tubeswell

    tubeswell Friend of Leo's

    Jul 1, 2008
    NZ

  6. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Wow, Tubeswell's way is super elegant and would be super safe and easy. I'm doing that in the future!

    *If and only if* you can't find one of those insulated screw terminals, you could actually use the 3-lug terminal strips Mojo sent you. Recheck my post back around #151 (you've not only built an amp, you've built a reference manual) -- I attempted to show you my method, but the pic may be unclear.

    One other possible option (failing the insulated screw terminals) is your hardware store across the street -- they might have the delightfully named 'butt splice connectors' (cue Homer Simpson) which let you splice two wires with just your wire strippers and crimping tool.

    I used to heat shrink over a soldered splice in space (Google 'western union splice') but it isn't easy or especially robust. Wire nuts *are* sometimes used but if I read right, amp guys tend to wince a bit when they see this done.
     

  7. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Very helpful, King Fan! Thank you. I'll see what the hardware store has. I can also ask my neighbor, who is a mechanic of every sort and has just about everything under the sun. I also have some incoming zener diodes to give him: 100V ones and 12V 1/2 watt ones. :) They're no good to me. But now I'm on the right track there, thanks to @tubeswell.

    As far as building a reference manual, I'm sincerely sorry if that's annoying. But it was a part of my goal of asking as many questions and being as thorough as possible. On some of the build threads, amps magically appear a few posts after the initial build was begun, and they're all working. That does nothing for greenies like me, who can only assume: "Well, I guess they really know their way around electronics." I'm hoping that this thread will be a good reference for future builders who don't know jack, like me. Thanks for being so patient and so helpful. You and @tubeswell have been, well... swell.
     

  8. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    LOL, I was being sincere about the reference manual. Future builders will thank you for your thoroughness and your wish to know. :)
     

  9. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    One more note of what I hope is good news. Like Jeremy, Richard, and James, I keep a tame racing driver, er, amp tech. Let me just say, "I call him the Stig." When I asked him about the switch on the tone pot, he said this (edited a bit for brevity):

    "So you have a rotary off switch on the tone pot, wired to disconnect the tone pot wiper from the volume pot input when the tone pot is turned all the way down? If so then, when it is turned off, the full 1 M of the tone pot's resistance is between the 500 pF bright cap and the bigger, grounded (.005uF) tone cap. So that should sound very stock champ."
    I'm not positive that's right, because poor Stiggy has to rely on me to explain what I think is going on, but pending correction or insight from our own pros, I'm gonna leave my switch the way it is. I liked the idea of Tubeswell's dual-lift switch, or Rob's separate switch on the ground leg that would leave the tone pot to function as a variable-bright-cap pot, but I'm not eager to drill a hole in my chrome faceplate to install such a switch.

    As I say, I may be wrong, but it's been several minutes now since I was wrong last... :)
     
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  10. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    See my post 220
     
    Last edited: Nov 13, 2017
    tubeswell likes this.

  11. tubeswell

    tubeswell Friend of Leo's

    Jul 1, 2008
    NZ
    Re: the tone stack lift, you actually could use two relay switches (to cut the tone pot in 2 places) which are activated solely by the SPST switch on the back of a 1M pot, but you need to rig up a DC supply for the 2 relay switches (which you could do with 5V relays on a DC rectified power supply off the end of the heater winding, which would also involve grounding the heater winding differently). And so there are a lot more wires, parts and problems to troubleshoot. But its feasible. But we shouldn't go there on a 1st build.
     
    King Fan and RLee77 like this.

  12. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Thank you, RL, I'd missed that. I was feeling kinda bad about telling Prof he could do this -- although I did it myself and liked the results. I'm pleased to know I can down put my soldering iron and back away...
     

  13. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Thanks for this, RLee. Somehow I missed the beginning of your post #220 as well. Yes, I did that, but I forgot to mark it.

    As far as the tone pot goes, I'm glad to know that the current configuration may not yield an audible difference from the way it "should" be if one were to remove the tone stack entirely. At any rate, I liked the sonic results with the tone pot as I have it during my brief rendition last night.

    King Fan: "STEP AWAY from the soldering iron!" ... :)
     

  14. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Hey @tubeswell - Look what I found at the store tonight: a 12-circuit terminal block for 22-10 gauge wire. If I understand you correctly, I'll chop/cut off the first two blocks, using the vertical hole between the insulated terminal slots to mount it to the chassis.
    terminal block.jpg
     
    tubeswell likes this.

  15. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Now for some more stuff that I don't have to wire or build or measure somehow: I found some 1950's bakelite knobs from an old radio on Etsy. They're from Leeds Radio in the Bronx. Great price, too.
    IMG_9540.JPG
     
    King Fan and tubeswell like this.

  16. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    I'm also having a fellow TDPRI-er build the cabinet for me. It's @jsnwhite619 . It'll come with tolex, a 1x10 birch ply baffle, leather handle, glides, back panels, and oxblood grille cloth. And he'll give the tweed a good shellacking.

    Here are some pics of the initial stages of the build. The cabinet will be built for a 10" speaker (an Eminence 1028K). It'll be a little deeper for better bass response. The dimensions are: 16 1/2" H x 18" W x 9 1/8" (bottom) and 8 1/4" (top). [7/8" taper]

    I looked around a bit on the different dimensions for tweed Princetons, and this is what I got:

    Mojotone cab (1x8): (H) 16-5/8'' X (W) 18'' X (D) 8-3/4'', Chassis cut 11-3/4''
    Weber cab (1x10): (H) 16 3/4" x (W) 18" x (D) 9 1/4" (bottom) and 8 1/4" (top) [1 " taper]
    Narrow panel Princeton 5f2a (1x8)
    1955: (H) 12½” x (H) 13½” x (D) 8” [Look at how small that was!]
    1955-1960: (H) 16¾” x (H) 18” x (D) 8¾”
    Narrow panel Harvard 5F10/6G10 cab (= "big box Princeton") (1x10): (H) 16 1/2” x (W) 18” x (D) 8 3/4”

    pieces.jpg gluing.jpg 16.5 H x 18W x 9 1-8 up to 8.25.jpg
     
    Last edited: Nov 13, 2017
    tubeswell, keithb7 and RLee77 like this.

  17. keithb7

    keithb7 Friend of Leo's

    Age:
    46
    Jan 9, 2010
    Western Canada
    I was out of town and distracted from this thread for a while. I am pleased to check in and read so much great dialogue here.

    Not picking sides here , but for a beginner I can see the point here. Especially a builder who may be a hint OCD. A death cap in a modern amp kit? That comes with a grounded power cord? Seems odd to me too.

    I am equally impressed. Especially that all the gold writing is still on the F&T caps. Nor has any previously installed hardware been removed yet. I sense a very patient, thorough builder here.

    What is the ETA on the cab? With the progress you've made Professor, I know I'd be itching bad for that cab to show up ASAP. However looking at your work here, and witnessing your patience I'd only guess you are ok with waiting a while. I'm anxious and I live way up here!

    Cab builder is in Georgia? Nice. I have visited Georgia. I experienced some nice southern hospitality there.
     
    Last edited: Nov 13, 2017

  18. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    That cabinet looks nice, and I like the dimensions (and I assume there's lots of freedom in tweaking those if one sees fit)... I'll have to keep jsnwhite619 in mind when I do my 5F2a build, if he is interested in building for others.
     
    jsnwhite619 likes this.

  19. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    @tubeswell - Sorry to be thick, but let me see if I understand this correctly. I apologize that I'm still such a newbie that I don't understand all the terminology. I'll use this picture of my amp as it's wired now as a guide for my question (and perhaps your answer, too).
    IMG_9525.JPG
    The power transformer's high-tension winding's center tap is the red-and-yellow wire in the center, which is grounded to the chassis together with the black wire coming from the -ve side of B+1 (in my case, at the second eyelet at the top). There is also a yellow wire going down to the rectifier that comes off the +ve end of B+1 (in my case, at the first eyelet on the bottom).

    I take that red-and-yellow wire, and I attach it to the zener +ve terminal. Then I take the _______ wire and hook it to the zener's -ve terminal. I assume that the ground return bus is the black wire, since that's the one that's going to the -ve (grounded) side. But am I correct?

    If so, it sounds to me like I'm simply putting 3/ 12V, 5W zener diodes between the red-and-yellow wire and the black wire that are grounded together in this photo. Is that correct?

    Part of the reason I ask is because I want to do it correctly. But I'm also trying to figure out where to put that piece of insulated terminal block where I'll hook my white power cord wire and one of my PT primaries together when I re-wire that. I'm trying to account for space.
     
    Last edited: Nov 13, 2017

  20. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Very cool. I'll keep posting pics here so you can see the build in progress and then the result.
     

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