Tubegarden Harvard circuit

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Jim Collins, Sep 24, 2005.


  1. Jim Collins

    Jim Collins Member

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    Does anyone have a Tubegarden Harvard amp, or, better yet, has anyone built one of these kits?

    A friend bought one of these kits, and asked me to build it for him. I agreed to do it -- I've built several amps from kits, and I like doing it. Of course, when it arrived (a long time ago), there were no instructions, at all. After quite some time, Dan sent us a layout of the circuit board. That was helpful, but it only tells half the story.

    This amp is based upon a Fender tweed Harvard, the 5F10 circuit, but it is not a clone. There are several differences, enough that I would not be able finish it from a Fender schematic or layout. (I have each of those.)

    If anyone has built one of these, could you send me a copy of the instructions? Dan, from Tubegarden, has been promising instructions for nearly a year, but nothing beyond the circuit boad has appeared.

    Thanks loads.
     
  2. tonezoneonline

    tonezoneonline Member

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    I understand it's not an exact clone but with Dan's layout and the Fender schematic you should be able to figure it out without much trouble.
    I've never seen any of Dan's kits but could probably help you if you posted the specific problem your having?
    If nothing else use a process of elimination.Use all of the componnets that do match and then see what's left.If it's a transformers issue,who's the manufacturer?
     
  3. Jim Collins

    Jim Collins Member

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    It is significantly different from a Fender Harvard. For instance, the input section is different. The Fender has three inputs, and each uses a 68K resistor. The Tubegarden has two inputs, and Dan told me (back when he could be reached) that his design does not use them. He told me it is basically a low power tweed Twin preamp with a Harvard power amp, but even the low power Twin uses these 68K resistors. The original uses one 6AT6 and one 12AX7, whereas the Tubegarden uses two 12AX7s. The original had no bias adjustament, whereas this one does. Even the heater elements are wired differently, though I can figure that out, easily enough.

    The problem I'm having is that I only have a circuit board layout. I have nothing else, and this more of a Fender-inspired design, rather than a close copy. We can't even get Dan to send us a schematic.
     
  4. tonezoneonline

    tonezoneonline Member

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    The issues you have mentioned are still relatively simple for someone with a little tube knowledge to work out.No matter what Dan has done he has not changed basic tube design.
    He has not changed the pins the plates are on or the pins the heaters are on .The addition or deletion of a bias adjust is also a simple matter.Your just subbing a variable resistor (pot) for one that is fixed.
    I imagine the amp still has the grid reistors(68K) too.Dan has maybe moved them to the board,tube sockets or maybe changed the value slightly.
     
  5. Roe

    Roe Member

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    i've heard on the weber forum that tubegarden has stopped shipping amps. Even people who have paid havn't recived their amps.
    Have anyone of you had problems with tubegarden?
     
  6. Jim Collins

    Jim Collins Member

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    Dan told me he does not use the 68K resistors, and there are none in the parts.
     
  7. TheAmpNerd

    TheAmpNerd Member

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    Wow, how does the amp work without imputs?

    Yes, I don't mean to be rude, but
    I think you are in over your head. With his layout, you
    should have no problem building the amp unless the
    layout is missing stuff (like connection points and what
    resistor goes to what eyelet or terminal to what pot,
    etc.
    Well the heater elements typically
    work one of two ways, AC which typically doesn't
    matter which wire goes where (on the correct pins)
    and DC, in which you have to ensure the pos and the
    neg sides (tube pins)don't change).
    Oh Chit, sorry to hear that. Best to take it to a tech
    and have him work it out--really. You should have a
    complete layout and schematic especially if it is a kit.

    Someone who has built amps and serviced them for
    a while should have only slight challenges with that
    kit, namely how you would like it to sound/set up.

    Find someone.

    Good luck and keep us informed.
     
  8. Jim Collins

    Jim Collins Member

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    I was thinking faster than I typed. The amp has two inputs, rather than the three inputs of the Fender tweed Harvard. That should have been the end of one thought. The next thought was pertaining to the 68K resistors. Dan said he didn't use those, though the Fender tweed Harvard does use them.

    I'm in over my head? Of course, that's why I posted, in the first place. I've built amps from kits, when those kits have instructions. This is a kit, and it was supposed to have full instructions. It has none, at all. Some number of months after my friend received the kit, Dan posted a pic of the circuit board layout, and nothing more. All other instructions are missing. And I stress, ALL other instructions are missing. All I want to find out is if someone has built this critter, and has instructions.
     
  9. TheAmpNerd

    TheAmpNerd Member

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    Missed the pic, but that is not important.
    Contact the seller of the kit, who ever he bought it
    from, they should stand buy what they sell, or
    at least get your money back.

    There should be a grid stopper on the input
    just for safety's sake whether on the tube pin
    or on the board.

    Follow this layout:
    http://www.ampwares.com/ffg/schem/harvard_5f10_layout.gif

    Eliminate number 3 input jack.

    Print it off and double check the components
    and go.

    Print it off large, the lay your components out
    on the paper print out and see what is missing
    different.

    Just don't use the heater wired to chassis ground.
    Some other stuff for safety and noise reduction also.

    Don't panic, do the best you can at first there are
    plenty of folks here to help you out. Just make sure
    you can take pictures and explain what your doing
    as best as you can.

    Posting the layout and comparing it to the
    link I gave you should be a big help.

    This is a straight forward simple build for folks
    with experience, it will be more challenging for
    you, but you will get there.

    So find the tweed twin layout and print that off.
    There you will have your two 12Ax7s and the parts
    in the kit.

    Probably this amp:

    http://www.ampwares.com/ffg/schem/twin_5e8-a_layout.gif

    Just eliminate left input 1-2 jack, tube and wiring;
    shifting the coupling over to the V1 (the far right tube.
    You should be fine then. Take your time and figure it
    out. You've built kits so have a go.

    Also don't use the 4 100K resistors and wiring
    of the left 1-2 inputs and the .02 cap.

    Use those values for the V1 in
    the harvard amp.

    I guess it uses the same 12AX7 PI and output
    section of the Harvard amp if you want bright
    channel at the caps on the volume 2 pot.
    Also eliminate one of the 270K channel
    mix resistors (from the volume pot.)

    Do you have the Presence, Bass, Treble?
    Then wire those in too.

    His layout should be the clue.

    Post it here if you can.

    Good luck and have fun, take your time
    and be safe.
     
  10. tonezoneonline

    tonezoneonline Member

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    Jim,
    I'll be glad to post the layout on my server and post the URL if you need a place.
    Ask specific questions as to what the problems are and we can help you.
    Dan said this and Dan said that just don't help.
    Or just send the amp and a credit card number my way and I'll take care of it:) Just kidding .
     
  11. Jim Collins

    Jim Collins Member

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    All I really intended, by posting the original question, was to see if anyone had built this amp, and, if someone had built it, were the instructions still available. I have come into contact with one other person who is looking for instructions to this very same kit, but I have not come into contact with anyone who has built it.

    The seller of the kit is Tubegarden, and getting him to stand by his product is proving fruitless.
     
  12. TheAmpNerd

    TheAmpNerd Member

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    Perhaps you
    and the other guy are the only two.

    It is also possible the "Kit" never worked right
    to begin with and you are a casulty.

    If I were a betting man, you will never find instructions
    and a proper layout.

    However, I definitely would take tonezone up on his
    offer. Lot's of help is here, everyone can do their
    part. AND your buddy that has one also can come
    and do his at the same time.

    RESULT

    Two guys end up having kit amps that work.

    Good luck what ever you decide.
     

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