1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

Harvard in a 5F2A Chassis Build

Discussion in 'Shock Brother's DIY Amps' started by James Knox, Nov 22, 2020.

  1. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    The Bias End of the board

    0D3C73A7-A800-4BF4-9F11-7BA86286D5C4.jpeg

    The Volume and Tone Control

    BE49BE41-3FFC-46E0-800D-12D881F56951.jpeg

    The Input Jacks

    AE634B2E-2672-45F6-B273-5735556FBC06.jpeg

    V1, V2 and Speaker Jack

    2677B7FC-4CC9-40F9-98E4-9E1B6AAA19BC.jpeg

    Power Section Ground, Separate AC Ground, Heat Shrunk Fuse Block. Over to Bottom of Chassis, making room for 1/10th Power Switch in its place. Protection Diodes on Rectifier Tube Socket.

    C6A23E2A-3E67-40C5-83AD-4146CAD0349D.jpeg

    Lamp Assembly, 25 Watt Thermal Pasted Resistors for 1/10 Power Mod.

    4C0659E4-0B51-4B4B-BF45-4D5605AF8540.jpeg

    Power Tube Sockets with 3 Watt 470R Screen Resistors. Cathode to ground (will replace with 1 ohm resistors when they arrive).
    4ECE9841-32A8-494F-A0A6-81703662A5C8.jpeg
     

    Attached Files:

    screefer, drew1d and King Fan like this.
  2. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Closeup of the 16ohm and 12ohm 25 Watt Resistors


    C2368F1A-2D46-4D08-B91C-703BAF166BBE.jpeg

    Right hand side of the Hoffman Board.

    CA98BB00-0881-4D50-BD7B-85A10D18AF0E.jpeg

    My New Favorite Knobs for my Tweed Builds. A More Modern Chicken Head?

    3ED3447F-695F-4FBE-85F4-1D6CD9CCD273.jpeg
     
  3. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    I grounded the Heater CT with the Power Side ground. This thing is dead quiet. Maybe not needed or worth it!
     
    Lowerleftcoast and Kevin Wolfe like this.
  4. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Thank you LLC. You always inspire me to build better and with more understanding. I will try this once I figure out what my numbers are supposed to be.
     
    Lowerleftcoast likes this.
  5. Kevin Wolfe

    Kevin Wolfe Tele-Holic

    Age:
    63
    Posts:
    542
    Joined:
    Jun 13, 2017
    Location:
    Lakeland FL
    Lookin’ great James. Love those knobs too!
     
    James Knox likes this.
  6. BigDaddy23

    BigDaddy23 Tele-Holic

    Age:
    47
    Posts:
    674
    Joined:
    Jan 4, 2019
    Location:
    Australia
    Beautifully executed, James! How you liking the power soak resistor mod? What % volume do you think it drops?
     
    James Knox likes this.
  7. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    I am LOVING it! I rigged one up in a pedal box to try out back when I built my 5E3. Tried it a couple of times. Then kinda forgot about it. But with this amp - wow! It everything I wanted the Deluxe Micro, Boothill Six Shooter and Champ to be! I seriously could not stop playing it yesterday. Creamy warm overdrive with a Tele straight into the amp, Volume all the way up. Probably about 1-2 watts. Make this amp an amazing practice or recording tool AND plenty of Volume to Gig with. If we ever get to gig again, lol.
     
    gabasa and BigDaddy23 like this.
  8. mjcyates

    mjcyates Tele-Meister

    Age:
    57
    Posts:
    489
    Joined:
    May 4, 2010
    Location:
    Louisville, KY
    Nice job! congrats!
     
    James Knox likes this.
  9. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Do you still have and play through yours? Is there an amp you like better?
     
  10. mjcyates

    mjcyates Tele-Meister

    Age:
    57
    Posts:
    489
    Joined:
    May 4, 2010
    Location:
    Louisville, KY
    No I sold mine but it has been one of my favorites so far. I also really liked the 6G2 that I built.
     
    James Knox likes this.
  11. screefer

    screefer Tele-Holic Silver Supporter

    Posts:
    673
    Joined:
    Feb 28, 2016
    Location:
    kildonan
    Super nice and inspiring...Congrats!
     
    James Knox likes this.
  12. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,441
    Joined:
    Dec 30, 2019
    Location:
    california
    Looking good!
    I am impressed with how your skills have improved. The soldering is much nicer on this build. Are you liking an eyelet board better than a turret board?

    If you can tear yourself away from playing the Harvard, get a voltage chart to us so we can all compare our future builds.;)
     
    screefer and James Knox like this.
  13. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Thank you for your kind words. Yes, I like eyelet over turret. After a 5E3 with turrets, never again, lol. Plus I like the way solder flows in eyelets. Also easier to swap out components.

    Good reminder to get the voltages in here. I will get to that.

    This morning I’m studying How To Bias (RobRob), working with the Bias Calculator, playing, listening and comparing. If I’m measuring right, my dissipation percentages are really low (less than 30%) so I’m working with the 470k jumpered with the 27k like you suggested earlier
     
    King Fan and Lowerleftcoast like this.
  14. Huddy

    Huddy Tele-Holic

    Age:
    38
    Posts:
    745
    Joined:
    Nov 5, 2016
    Location:
    Newport News, VA
    Gonna need some sound demos!
     
    James Knox likes this.
  15. King Fan

    King Fan Poster Extraordinaire Ad Free Member

    Posts:
    6,384
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    That is low. Possible for sure. You might share the measurements/methods you’re using...
     
  16. Junior Little

    Junior Little Tele-Meister

    Posts:
    301
    Joined:
    Jul 26, 2018
    Location:
    Rural Illinois
    Hey @James Knox! Nice build; been following along with interest as a Harvard is my next planned build. Just curious: why did you not use the ClassicTone 40-18022 output transformer?
    I happen to have one in my spares shelf and planned on using it for my build, then I saw that you opted for the Hammond 1750E. Any particular reason for the change?
    Thanks!
    And awesome work!!
     
  17. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Wanted to bring a little update to the Bias section. I started off not really understanding how it worked but reading and re-reading RobRobs “How to Bias” Tutorial and some “hints” from @Lowerleftcoast, @King Fan and @zook I did the maths and calculated the range I wanted my bias pot to operate in. Then I piggybacked, substituted, measured, soldered and unsoldered till I found the magic combination for that range. I went through all these...

    E633BF0B-081D-4256-84B1-AA083A38C50B.jpeg

    To find the Dropping/Tail resistor combo That allows me to adjust from “cool bias” (50%) to “average” (60%) to “maximum safe” (70%).

    I ended up with a 120k dropping resistor and a 22k tail resistor. (Just for fun and to learn, I ended up trying 10k, 22k, 27k, 33k and even piggy backed 470k on the 22k and 27k.) Here is the final product...

    44360A55-8121-421A-9D7C-CBD3E5B66F4A.jpeg
     
    BigDaddy23 and Lowerleftcoast like this.
  18. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    I will be working on that. I have not Had a way to record, having just an iPad and iPhone, so I got one of these to mate a SM57 and my iPad. Haven’t even opened it yet, lol.
    10A76641-F446-443B-B10E-1C02374A49BB.jpeg
     
    Huddy likes this.
  19. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    I got this part...
    1AD20202-F6EF-490F-A128-AC484D905BE1.jpeg

    But confused with this...

    8ADCA3B1-821E-48F2-8B39-7D7BBBD31B2A.jpeg

    Plate Current Voltage Drop (29) divided by OT Resistance (148.1). I get .195813 amps, or 195.83 Miliamps.
     
  20. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    939
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Thanks man! I like both Classic Tone and Hammond Transformers. Mostly been using Hammonds cuz AES is close and I get fast and free shipping. When I heard ClassicTone was going under, I bought a matching PT and OT for a future build, thinking maybe the Harvie. When I discovered that the PT wasn’t gonna work I decided to keep them together for something else down the road.

    I’ll be watch in’ for your Harvard build!
     
    Junior Little likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.