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Micro Deluxe Build

Discussion in 'Shock Brother's DIY Amps' started by Meteorman, Jun 9, 2019.

  1. Meteorman

    Meteorman Tele-Afflicted

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    Thank you Jake.
    Found my problem after a little chopsticking - sigh - cold solder joint on the OT input from V2.
    Fixed that and it's alive now.
    Output volume seems weak tho' - if I crank Vol and Master Vol ALL the way up, it gets to about "easy listening in your living room" volume.
    I'm guessing this isn't spec, compared to my other Champ and 5E3 builds, for which turning Vol to 10 is not allowed in the house.
    I have the 3.5W Hammond 1750A OT hooked up to a 8ohm Weber Signature 10".
    Any tips on where to start chasing that down that would be greatly appreciated.
     
    Last edited: Jun 29, 2019
  2. robrob

    robrob Poster Extraordinaire Ad Free Member

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    It should be louder than that. Let's start with all the voltages on all the tube pins. If that checks then we'll start verifying resistor values and wiring.
     
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  3. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    So can you still lift the lid? Is inspection limited? Not sure it would help, but I've been seeing good reviews on cheap fiber-optic cameras that plug into your cell phone.
     
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  4. Meteorman

    Meteorman Tele-Afflicted

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    Will attempt to gather that data.
    It is a little tricky given the limited access to socket tabs, but i think i can do it - carefully.
    I try to verify resistors as they go in but Lord knows Murphy could have paid a visit. I’ll go over them again.
     
  5. Meteorman

    Meteorman Tele-Afflicted

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    Couple steps of maybe progress:
    PT is a Hammond 290CAX 275-0-275.
    I have a new Electro-Harmonix 12AY7 in V1 and a new Tung-Sol 12AU7 in V2

    Probed the sockets this morning:
    V1A plate: 151
    V1A cathode: 2.2
    V1B plate: 149
    V1B cathode: 2.3
    These seem pretty close to your/Rob's values on the Micro deluxe site.

    Initially,
    V2 plate: 361
    V2 cathode: 14.6
    B+ line at OT: 384

    Plate seemed low and cathode seems high compared to your/Rob's published values.
    I had initially swapped in a 680ohm dropping resistor between B+ and B+1.
    After seeing values above, this morning I replaced that with the original spec 470ohm voltage dropper between B+ and B+1, and....

    NEW V2 plate: 367
    NEW B+ line at OT: 389
    Still seem a little low ?
    And a 14.6 cathode is high - unless I should be dividing that by 2 since the pins 3 & 8 are jumpered ?

    Volume did sound a little higher to me, altho maybe it was mostly wishful thinking.
    Not sure it's where it should be yet.
    Should I go lower still with that resistor between B+ and B+1, and get plate voltage closer to 400 ?

    thanks muchly guys.
    As always, the members of this forum are a tremendous asset to us weekend warriors, and greatly appreciated.
     
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  6. robrob

    robrob Poster Extraordinaire Ad Free Member

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    You'd be hard pressed to hear a volume difference between 389 and 400v B+. You're fine where you are.

    What kind and size speaker are using? A typical 12" speaker will be freakin loud with this amp maxed.
     
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  7. Meteorman

    Meteorman Tele-Afflicted

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    got a 10" weber signature ceramic.

    Took some days off to go down to DC and catch the Stones gig.
    I'll be getting back on this project this weekend.
     
  8. Meteorman

    Meteorman Tele-Afflicted

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    Assembled it and played it thru the Weber 10” ceramic.

    With vol and mastr vol maxed, the volume is such that I can play it in house and the missus still won’t quite yell at me. Can’t help but think I’m still missing something.

    I used 22ga solid hook-up wire from the pots and sockets.

    If I could play better I’d post a clip, but as it is, I don’t think it’d help.

    Here’s some gut shots and after assembly.

    Maybe someone can see what might be restraining the volume….. Some may look a little sunken, but I feel pretty good about the solder joints – I donned my OptiVisor and went over them and reflowed many.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
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  9. FenderLover

    FenderLover Poster Extraordinaire

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    Compare the layout to the schematic. The layout does not match the schematic at the Master. The layout shows the 470K 'V2 grid stopper' going to the Master pin 3, and the Master pin 2 going to the output grid. The schematic shows the output cap going to the Master pin 3, and Master pin 2 going thru 470K to output grid. The schematic wiring will give more output, or at least more saturation.

    And...Damn! That's a cool build!
     
    Last edited: Jul 9, 2019
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  10. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Good catch FenderLover. I moved the 470k resistor to before the master volume to cut some signal to prevent "strange" overdrive behavior at max master volume with some high output pedals. I forgot to update the schematic.

    Meteorman, jumper around the 470k resistor for a boost of output and see if it gets you to where you want to be. If you like it you can put the 470k resistor in the path between the master volume output and the power tube.
     
  11. Meteorman

    Meteorman Tele-Afflicted

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    Many thanks gents.
    So i moved the Master lug 3 wire to the output cap (i.e. the R470K out of line now).
    Unfortunately, i could detect no discernable effect in volume.

    i'm an electrical hack, but this seems to suggest a coupla diagnoses to me:
    (1) there's an issue downstream of that modification still choking volume, or
    (2) the 470K needs to go in line between master vol and power tube in order to complete the output improvement.

    I'm guessing #1.
    I'm gonna try a different speaker, tubes, and maybe start chasing down some of hook-up leads using this cheapa*s solid wire.
    Anymore thoughts I'm all ears ! Thanks again.
    /mike
     
  12. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The problem doesn't have to be downstream. You could be losing signal upstream too.
     
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  13. Meteorman

    Meteorman Tele-Afflicted

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    Checked all my resistors and did a resistance check on all the hook-up leads, thinking I mighta broke/cracked a solid wire. They all registered .3-.4 ohms, which I assume is OK.
    Noticed I had some funky value caps in for the tone cap (330pF) and a 2nd bright cap between lugs 2 and 3 of master volume.
    Don't know if that was my issue, but I removed the MV bright cap, and changed the tone cap to a 4700pF.
    It sounds a louder to me now. It won't rattle the windows but that's OK, I don't play well enough to do that anyway.
    It really cranks through my ATH700MK2 headphones, which was the feature which sorta drew me to this build in the first place.
    It now sits on my tweed Deluxe build, and I'm likin it !!!

    [​IMG]
     
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  14. richa

    richa Tele-Afflicted Ad Free Member

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    Lik'n that alot. Especially the headphone aspect. Very cool.
     
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  15. Meteorman

    Meteorman Tele-Afflicted

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    I finally took the time to tear this thing apart to try and solve the low volume problem.
    Allowed me to incorporate some of the tweaks Rob has made to the layout since I first put it together.
    Plus I reconfigured the whole assembly to get the tubes and PT up out of the interior of the case.
    I noted that the 1M resistor on the input jack was reading about 500K. Assume that might be where my signal was leaking to ground ?
    Fixed that, re-configured the assembly, and it performs very nicely now. Volume is good and the headphone-out feature gets a lotta use.

    [​IMG]

    [​IMG]

    [​IMG]
     
  16. awasson

    awasson Poster Extraordinaire Silver Supporter

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    Aha! This is that amp you posted a photo of in the thread about using Hammond boxes. Glad to be able to read the whole thing. What a great form factor. I think I have to do something like this. It’s the perfect living room rig.
     
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  17. BigDaddy23

    BigDaddy23 Tele-Holic

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    Great build, man! Well executed!
     
  18. Meteorman

    Meteorman Tele-Afflicted

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    thanks gents.
    It is indeed a big sound out of a small box... thank to Rob for that !
    A committed player who travelled a lot for work could actually pop the tubes in their pocket and plane travel with it in their checked luggage, along with a pair of headphones.
    Make all those nights in strange hotels a little more bearable.
     
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