Princeton Reverb Scratch build

Discussion in 'Shock Brother's DIY Amps' started by 2pupwonder, Feb 1, 2017.

  1. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,553
    Joined:
    Dec 29, 2012
    Location:
    United States
    Everyone says that about Hoffman. Someone posted on a facebook amp forum that the order they placed tomorrow arrived today :D
     
    clintj and King Fan like this.
  2. King Fan

    King Fan Friend of Leo's

    Posts:
    4,249
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    FWIW I built my PR with the most stock PT and OT I could. Sounds amazing.

    People who gig, or who need bigger, tighter sound, or a cooler PT, reserve amperage, and added potential durability, may well upgrade their OT or PT or both. But all those old original PRs that created the amazing rep didn't have 'em.
     
    arielyitus likes this.
  3. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    cabinet building pics:
    IMG_20170204_130424.jpg
    Laying out the sides - should have waited for the chassis as the top angle is wrong - live - n - learn, at least it's an easy fix.

    IMG_20170204_134013.jpg

    i cut a bevel on the top and bottom boards to match the angle of the adjacent sides.


    IMG_20170204_140428.jpg

    here you can see the two sides aligned with each other, i made them a 1/8" longer at both ends so i could true up the box joint with a straight router when complete.

    IMG_20170204_140931.jpg

    i clamped the sides together and trued up the cut edge with a very expensive pieces of equipment someone was going to throw away...
     

    Attached Files:

  4. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    IMG_20170204_142621.jpg
    Laid out the box joint, it's going to be 3/8 wide 'teeth'...

    IMG_20170204_145147.jpg
    i cut the box joint in with a jigsaw and a clean cutting cabinet blade. here you also see the back side scoring i did with a 1/4" chisel. go about 1/4 of the way thru the board when scoring on a soft wood like this. scoring the back prevents blowing out the wood... rubber dead blows make short work of this kind of thing.

    IMG_20170204_145728.jpg

    here's a completed piece. Blowouts happen... i pulled that piece out and used a special resonant wood putty to fill it in... it' like 50 bucks for a half oz can... Also, when freehanding box joints like this, only do one side of the seam... use the first cut seam to scribe out where your next cuts go.

    IMG_20170204_154908.jpg

    here's a dry fit. this one didn't require any filing. one joint did, due to a bit more crowning down the center of the board...

    IMG_20170204_174922.jpg

    here's the glue-up. it was near freezing in the workshop, so some of the glue on the bench was clouding over. i used standard Tite-Bond and ratchet straps for clamps. then i brought it into the house so the rest of the glue didn't freeze...
     
  5. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    IMG_20170204_174934.jpg

    This is another view of the clamp up. couple tips if anyone else is doing this. put glue on both surfaces. Also label all of your parts. Titebond sticks really good, even in 10 minutes. ALso, i sanded the inside surface of all my parts before assembly. didn't want planer marks inside my cab, probably make funky standing wave reverberations...
     
  6. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    also, my chassis showed up from Zach. it's a really nice piece he even thru in a black blank face and back plate... just need to add water slide decals to them... Knobs showed up - direct from china a dozen for what everyone wants for one knob...

    other stuff from Amplified Parts is due in tomorrow... Free shipping is cool, it just takes for ever...
     
  7. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    IMG_20170209_183453.jpg

    Picked up my G10 and cut it to size. I got the 1/8" easy cut electrical insulating variety. It's basically Formica plastic laminate (phenolic resin) with a small amount of glass fiber in it.

    IMG_20170209_202509.jpg

    Drilled all the holes per Hoffman's template.

    Also mounted the turrets. is it ok if they are slightly wiggly after staking? or do i need to go thru and tighten them up with a flatter staking tool?
     
  8. tresspassor

    tresspassor Tele-Meister

    Age:
    45
    Posts:
    280
    Joined:
    Jun 17, 2010
    Location:
    Austin
    I did one using hoffman's AA1164 layout for a PR-ish and it turned out really quiet. Here's a link to that build thread. Looks like the pic links are broken, but there's a direct link to the pics folder in there somewhere.
    http://www.tdpri.com/threads/kingston-reverb-build.511559/

    I would recommend to tighten up the turrets. You could risk pulling one out when doing some future repair, and that would be a major pain to fix. If you don't have the proper staking tool, you can just lay it top-down on a hard surface and use a large phillips head srewdriver and gently tap on them with a hammer.
     
    Last edited: Feb 10, 2017
  9. Dan Miller

    Dan Miller Tele-Meister

    Posts:
    106
    Joined:
    Mar 22, 2011
    Location:
    Thousand Islands, New York
    I keep a bottle of medium viscosity cyanoacrylate glue (Hot Stuff) nearby for just this reason. Glue the chip back down and carry on.
     
  10. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    ok, thanks will do that. to bad i don't have the steel top workbench i left at my previous address... it had 3/16" thick steel that was trued up on the top of it for cabinet and furniture assembly...
     
  11. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    Got my order from Amplified parts. going to proceed with assembly. more pics to follow!
     
  12. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    it worked, they are all tight now. Thanks!
     
  13. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    So got it all together and double checked, i got a loud pulsating low pitch squeal when turned on.

    Does this mean my OT primaries are reversed?
     
  14. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    Also, i think i heat damaged one of the capacitors. the lead in it fell out on me. i put it back in and am going to order a replacement.
     
  15. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,553
    Joined:
    Dec 29, 2012
    Location:
    United States
    Yes, the squeal is probably positive feedback.

    I wouldn't turn on the amp again until you get that cap replaced. Use a heat sink on component leads when soldering. Even an alligator clip will help.
     
  16. 2pupwonder

    2pupwonder TDPRI Member

    Age:
    32
    Posts:
    68
    Joined:
    Dec 15, 2016
    Location:
    Windy City
    I reversed them and got normal operation.
    Thanks! I found a match at radio shack and replaced it. the amp sounds really good.

    The bass distorts before anything else, kind of farts out... which is normal and what the PRRI did that i tried out, only not as bad. Some of it is probably due to the speaker, which claims it's 30 watts. It's an old champ xd 10" i had on hand. Wasn't going to dump any more dough into this project till i proved it would work.

    Should i do Cathode resistors on the PI? i was thinking 470k as i have some spares... also have 33k and 470ohm leftovers.

    Got lots of pics to post, is anyone interested?
     
  17. D'tar

    D'tar Friend of Leo's

    Posts:
    2,291
    Joined:
    Jan 11, 2013
    Location:
    WNY

    Well........ um... yeah!
     
  18. Phrygian77

    Phrygian77 Tele-Afflicted

    Posts:
    1,771
    Joined:
    Apr 30, 2016
    Location:
    Crawfordville, FL
    What output tubes are you using? What did you use for the rectifier? What is your B+ and idle cathode current? The 6.6k primary moves the load line more towards class B territory.
     
  19. mgwhit

    mgwhit Tele-Holic

    Posts:
    874
    Joined:
    Aug 1, 2008
    Location:
    Louisville, KY
    Assuming you built a stock Princeton Reverb you already have cathode resistors on your PI -- it wouldn't work if you didn't. Do you mean a grid stopper resistor? If so, use the 470K.

    Yes! Please!
     
  20. CordovaNate

    CordovaNate TDPRI Member

    Posts:
    11
    Joined:
    Feb 18, 2016
    Location:
    Memphis
    I'm relying on the "better late than never" axiom to revive this post. I completed my build 1-31-17 and would have posted then had I seen this thread.

    I'd never built an amp before, but I saw a populated PRRI circuit board on ebay and thought I'd use it to build a PR. That didn't work, but I already had the transformers etc. I started my searching for parts & plans and found Hoffman, purchased what I needed from him.

    I built my own cab. I intended to use finger joints but my cheap table saw vibrated like crazy with anything other than a single blade and I figured it was gonna look ***, and I was in a hurry to play the amp, so I skipped that. I'm happy with it as-is though.

    My amp fired up on the 2nd try. A small piece of loose wire I was using to hold something in place was overlooked was shorting something out during the first try.

    I really enjoyed building it. Here is a link to way too many pictures.

    https://goo.gl/photos/bWWouxCUBKVYepLHA
     
    LudwigvonBirk, wblynch, sds1 and 2 others 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.