Harvard 5F10 Build

Discussion in 'Shock Brother's DIY Amps' started by mjcyates, Nov 14, 2018.

  1. Mr Ridesglide

    Mr Ridesglide Tele-Afflicted Gold Supporter

    Dec 11, 2009
    Bloomington, MN
    I may have misunderstood, but if you put them on the tube sockets you are also elevating the heater reference to ground. Maybe read a bit of this for more and better information than I could give.
    http://www.valvewizard.co.uk/heater.html
     
  2. mjcyates

    mjcyates Tele-Meister

    Age:
    55
    191
    May 4, 2010
    louisville ky
    Well I don't have any 100 ohm 1/2 watt resistors on hand but according to Merlin's article using 220 ohm 1/4 resistors is also acceptable. I do have some of those on hand from my pedal building stock. I wired them up to the pilot light and grounded to tab on chassis and that took care of the problem! You guys are awesome! Just for my education what is the purpose of the Red/Yellow center tap from the transformer?
     
  3. trippercaster

    trippercaster Tele-Meister

    420
    Aug 13, 2012
    Roanoke, VA
    Red and yellow is probably the center tap for the high voltage secondaries. Glad that solved it though. You can always say thank you by letting us hear it...

    Sent from my SM-G960U using Tapatalk
     
  4. mjcyates

    mjcyates Tele-Meister

    Age:
    55
    191
    May 4, 2010
    louisville ky
    I don't really have a good set up for recording but I will see what I can do:)
     
  5. jsnwhite619

    jsnwhite619 Friend of Leo's Ad Free Member

    Age:
    34
    Sep 10, 2013
    Georgia
    With some chopsticking and pushing some wires around, I got mine as silent as any I've built. Knob on 12 you literally couldn't tell it was on without looking at the light. I think the bare bones circuit leaves a lot of room to place things without being too close to other components.

    Sent from my XT1585 using Tapatalk
     
    robrob likes this.
  6. mjcyates

    mjcyates Tele-Meister

    Age:
    55
    191
    May 4, 2010
    louisville ky
    Mine is pretty quiet now. When turned to level that I will be playing at it is almost silent. This thing gets pretty loud! I was at first not so sure about the need for 3 different inputs but they definitely make a difference. Here is a picture in a roughed out head cabinet. I need to round corners, sand and stain.

    [​IMG]
     
  7. jsnwhite619

    jsnwhite619 Friend of Leo's Ad Free Member

    Age:
    34
    Sep 10, 2013
    Georgia
    Good job! Yeah, they can be a lot louder than people expect for a "little Harvard". Starting raising that NFB value and it gets a lot louder too. I know what an efficient 1x12 can do with it, I can only imagine that head with a 4x10 or 4x12 cab. When I took my Vibrolux to the local music shop back when I had it biased around 370v and 70%, the guys there guessed it was a 25-30 watt amp.

    Sent from my XT1585 using Tapatalk
     
    rjtwangs likes this.
  8. cottontails1959

    cottontails1959 TDPRI Member

    Age:
    59
    4
    Jan 23, 2019
    Pittsburgh, PA
    Wow, nice build. Any chance you would post your final schematic? I was thinking of doing one of these for a first build. I like the two-power tube, low-watt with simple controls.
     
  9. mjcyates

    mjcyates Tele-Meister

    Age:
    55
    191
    May 4, 2010
    louisville ky
    Thanks! Mostly used the stock Fender schematic. Attached is a layout file that shows how it is currently built.
     

    Attached Files:

    rjtwangs likes this.
  10. mjcyates

    mjcyates Tele-Meister

    Age:
    55
    191
    May 4, 2010
    louisville ky
    PT is Hammond P-T290BX, OT is Hammond 1750E
     
    rjtwangs likes this.
  11. rjtwangs

    rjtwangs Tele-Holic Silver Supporter

    Age:
    71
    996
    Jan 18, 2010
    Reston, Virginia
    Every time I turn mine on and crank it, my neighbor thinks i'm using a big amp, it just makes me laugh. It's a great amp, hope you have a lot of fun with yours!!!

    20190221_131222.jpg



    RJ
     
    Mr Ridesglide likes this.
  12. mjcyates

    mjcyates Tele-Meister

    Age:
    55
    191
    May 4, 2010
    louisville ky
    Nice amp! Yes it can get quite loud!
     
    rjtwangs likes this.
  13. Lynxtrap

    Lynxtrap Tele-Holic

    655
    Feb 29, 2016
    EU
    No grid leak on the the first tube?
     
  14. mjcyates

    mjcyates Tele-Meister

    Age:
    55
    191
    May 4, 2010
    louisville ky
    So I've gone back and forth on this topic. The original Harvard schematic does not have a grid leak resistor as far as I can tell. Is that because it doesn't need one? I just watched the Uncle Doug video on this topic and it seems like a good idea to have one. What would be the benefits of having one or the drawbacks of not?
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.