Deluxe Micro build

Discussion in 'Shock Brother's DIY Amps' started by davesans, May 14, 2020.

  1. davesans

    davesans TDPRI Member

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    Hello everyone I started to go through my parts I have on had to build a Deluxe Micro. I will be using an old chassis I have from another project that never happened just received my output transformer. This is my first guitar amp build I build other tube related gear I am posting of my chassis layout if you thinks it looks good I am ready to start drill holes and move forward

    Thanks Dave

    amp2.1.jpg
     
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  2. dan40

    dan40 Tele-Afflicted

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    Welcome to the forum! Your plan looks fine. I would normally place the OT in the center of the chassis, right between the output tube sockets myself. The primary and secondary wires would pop through the chassis under the turret board and head straight to the sockets and output jack. Since you only have one power tube socket your placement should work fine though.
     
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  3. drneilmb

    drneilmb Tele-Meister

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    I like that placement for a single tube power amp. One primary is close to the B+, the other one heads right over to the power tube, then the secondaries come up right under the output jack.

    0510202213.jpg

    There's a similar layout on a one-tube triode/pentode rig. OT dead center under the output jack, red to B+, blue to the plate.
     
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  4. davesans

    davesans TDPRI Member

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    Ok I moved the output transformer to the center of the chassis ignore the hole in the center I have a piece of aluminum that will cover them up.

    amp2.2.jpg

    The board is mounted on the underside the wires from the transformer will run under it to the speaker jack.

    amp-board.jpg

    Thanks for looking
    Regards Dave
     

    Attached Files:

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  5. davesans

    davesans TDPRI Member

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    I managed to get all the holes drill in the chassis and did a mockup
    ampmockup.jpg

    i also did a mockup of the board all comments and question are well a second pair of eyes never hurts
    board-mockup.jpg

    Thanks for looking
    Dave
     
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  6. dan40

    dan40 Tele-Afflicted

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    Your board looks great! Just don't forget the ground buss for the first two filter caps and cathode resistor on the left of the board. If you haven't soldered yet, I might suggest pushing the power tube cathode resistor to the left just a bit more. They can get hot with use and you don't want to heat up the e-cap beside it. The more air space you have between them the better.
     
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  7. davesans

    davesans TDPRI Member

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    Thanks dan40 I appreciate it nothing is soldered yet so it won't be a problem move the cathode resistor. I do have a question about the 6.3 volt heaters the Hammond transformer doesn't a center tap Rob shows how to create a artificial center tap with two 100 ohm resistors which goes to the power tube cathode resistor. I was going to put a terminal strip in connect the two green heater wires with the two 100 ohm resistors with a wire to the cathode resistor and two wires one for V1 and another for V2 also I would use the terminal strip for the resistor and diode to power the LED
    indicator. This should all work without a problem or should I do it differently?

    Regards
    Dave
     
  8. BigDaddy23

    BigDaddy23 Tele-Holic

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    There needs to be one 100R resistor on each heater secondary wire going to ground to provide the artificial center tap.

    Using a 3 tab terminal strip works great as you have a ground tab (center lug on the strip) that mounts to the chassis and you can land each side of the heater circuit to the other respective tabs. Makes for easy connections. You'll have plenty of room on that chassis for this method - Given you are running the LED, it may be worth running 2 separate 3 lug terminal strips on either side of the PT, or get a larger terminal strip and locate the whole lot on one side. Note, the larger strips tend to have their attachment ground lugs on either end and not central for strength purposes.
     
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  9. BigDaddy23

    BigDaddy23 Tele-Holic

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    Here's a pic showing one I used in a Plexi build - red circle. Center lug goes to ground. Note the 100R resistors going to ground (center lug on strip) from the 2 sides of the heater circuit.

    You can see the red/yellow heater string heading off to the tube sockets and the green heater secondaries coming from the PT > Pilot Light > Terminal Strip. In you case, you won't have the pilot light so the green heater secondaries would go straight from the PT > Terminal strip.

    Running the center tap to the positive side of the cathode bypass cap provides heater elevation which can be a handy but not always necessary. You may well find the standard 100R pair to ground works fine. If there is too much heater hum, you can always move the tail/ground end of the resistors to a non grounded tab and then run a worse from there to you cathode bypass cap +ve to try the elevation method.

    Artificial tap.jpeg
     
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  10. davesans

    davesans TDPRI Member

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    Thanks BigDaddy
     
  11. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Your circuit board has a coupling cap grounded, which it shouldn't.

    I would also try to separate the V1B cathode resistor and bypass cap as much as possible (they may be vertically separated but I can't tell).
     
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  12. davesans

    davesans TDPRI Member

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    Thanks Rod I got confused with the black dot on the layout thinking the coupling cap was attached to the ground plane I corrected it now and moved the cathode resistor
    board.jpg
     
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  13. dan40

    dan40 Tele-Afflicted

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    Good catch Rob! I completely missed that connection. That would have made for some problems at first power up!
     
  14. davesans

    davesans TDPRI Member

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    I started wiring the chassis should be able to get some good progress over the long weekend.

    Regards
    Dave
    chassis-wiring.jpg
     
  15. davesans

    davesans TDPRI Member

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    I finished up the wiring I happened to wire the heaters wires to 5-6 instead of 4-5 on V2 I fixed that I going to double check everything again. Then start the power up procedure as per Rob's website. Report back soon thanks for looking.

    finishedamp.jpg
     
  16. davesans

    davesans TDPRI Member

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    Everything powered up just fine no smoke Yay! Here is my voltage readings

    B+1 334vdc
    B+2 281vdc
    V1A pin 1 178vdc
    V1A pin 3 1.47vdc
    V1B pin 6 179vdc
    V1B pin 8 1.49vdc
    V2 pins 1 and 6 332vdc
    V2 pins 3 and 8 2.68

    I have a 5751 in V1 and a 12AU7 in V2 I have a 12AY7 on it's way. It sounds really good on hum at all I was really surprised how loud in gets for the moment I have it plugged into the speaker in my Blues jr. Thanks to Rob for the great instruction on his website and everyone here for the help along the way this was a real fun build. I am going to build a cabinet and get a speaker for it. I will post some final photos and sound clips soon.

    Regards
    Dave
     
  17. jeff_e

    jeff_e TDPRI Member

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    Cool , nice work.

    I have another amp on the go, but may build one of these first, since I can't turn up the volume anyway with everyone staying home right now..
     
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  18. sds1

    sds1 Tele-Afflicted

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    Gosh sorry to drive by but I was looking at your voltages and now I'm confused. :(

    So it looks like you're using Hammond 269GX, it's 225-0-225 is that correct? So diode rectified B+ should be 315VDC max. Trying to figure out how you ended up where you did. What's your PT HT secondary and B+ measuring at?
     
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  19. davesans

    davesans TDPRI Member

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    I am using a Hammond 269GX and it is 225-0-225 I just took another measurement and think my first measurement was not under load.
    Voltages now are
    B+ 319vdc
    B+1 311vdc
    B+2 251vdc
    HT is 497v

    I hope that clears things up.
     
  20. sds1

    sds1 Tele-Afflicted

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    I guess your PT HT measures more like 250-0-250 unloaded then? If so, then it makes sense.
     
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