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.

I am about to start my first amp build.

Discussion in 'Shock Brother's DIY Amps' started by Ironwolf, Sep 5, 2020.

  1. Jason McG

    Jason McG TDPRI Member

    Age:
    49
    Posts:
    54
    Joined:
    Apr 8, 2020
    Location:
    Calgary Canada
    hey Ironwolf, I see Stewmac specs out a bipolar 250uF 25V aluminum electrolytic. what do they supply with the kit? mind posting photo of it, with the manufacturer and specs? I am following their build layout, but can't seem to find a bipolar cap. Wonder if it can be substituted with a standard polarized cap? thanks!!
     
  2. Ironwolf

    Ironwolf Poster Extraordinaire Gold Supporter

    Age:
    64
    Posts:
    9,283
    Joined:
    Mar 11, 2008
    Location:
    Boise, Idaho
    I have that one installed on the board already. It is marked as a Sprague Atom TVA1208. It is not marked as bipolar so I installed it with the markings oriented as the wiring diagram indicates. Hopefully, it is either bipolar or the orientation will be correct.
     
  3. _Steve

    _Steve TDPRI Member

    Age:
    40
    Posts:
    80
    Joined:
    Jul 14, 2020
    Location:
    Los Angeles
    Great thread and the build is coming along nicely!

    Would you mind taking a closeup photo of that sticker on top of the output transformer? I too am curious what iron they are supplying with the kit.
     
  4. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    2,292
    Joined:
    Dec 30, 2019
    Location:
    california
    The sprague datasheet lists the tva1208 as polarized so follow the markings.:)
     
  5. Ironwolf

    Ironwolf Poster Extraordinaire Gold Supporter

    Age:
    64
    Posts:
    9,283
    Joined:
    Mar 11, 2008
    Location:
    Boise, Idaho
    More info on the Sprague capacitor in question. The wiring illustration shows the turret 52 connection from the cap leading to pin 8 and pin 3 of V1. The circuit diagram indicates that the cap is oriented with the + towards V1 which is how I have it mounted. I am going to call StewMac to verify this.
     
    Jason McG and 8barlouie like this.
  6. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    2,292
    Joined:
    Dec 30, 2019
    Location:
    california
    I looked at the stewmac instructions. Yes, the positive side of the cap should be towards the V1 (turret 52).
    No worries.:cool:
     
  7. Ironwolf

    Ironwolf Poster Extraordinaire Gold Supporter

    Age:
    64
    Posts:
    9,283
    Joined:
    Mar 11, 2008
    Location:
    Boise, Idaho
    I received an answer from StewMac support, and they also confirmed the orientation of the capacitor is with the positive terminal towards V1, i.e. attached to turret 52.
     
    Jason McG and Lowerleftcoast like this.
  8. Mongo Park

    Mongo Park Tele-Holic

    Posts:
    937
    Joined:
    Nov 28, 2010
    Location:
    Winnipeg
    Since you have not put anything on the tube sockets I would twist up the heater wires a little mor at the sockets. At the sockets is where the twisting has a good effect since other parts And wires will be close bu on the sockets. Can’t hurt if you get him when it is finishes it is hard to get at the heater wires and twist them some more
    Cheers Ron.
     
  9. Ironwolf

    Ironwolf Poster Extraordinaire Gold Supporter

    Age:
    64
    Posts:
    9,283
    Joined:
    Mar 11, 2008
    Location:
    Boise, Idaho
    Worked on the turret board today.

    Got about half way through and broke for lunch.

    break for lunch.JPG

    By the end of the day I had everything populated (including the back which isn't shown). However, there was one part missing. a 1/2 watt 15K Ohm resistor which mounts between turrets 26 and 37. I already ordered a small pack which should be here Monday.

    almost done.JPG

    In the picture, some lead trimming remains to be done. It has been.

    I was asked to show the labels of the transformers. Here is the power transformer.

    power transformer tag.JPG

    And the output transformer.

    output transformer tag.JPG

    Tomorrow I'll take a soft tooth brush and my can of flux remover and give the board a good scrubbing.
     
    Jason McG likes this.
  10. Ironwolf

    Ironwolf Poster Extraordinaire Gold Supporter

    Age:
    64
    Posts:
    9,283
    Joined:
    Mar 11, 2008
    Location:
    Boise, Idaho
    Cleaned up the board and installed it.

    The testing did not go well. The initial voltage tests were spot on, but as I started testing the gain stages and tone stack circuitry, readings were all over the place.

    I began by retesting all the connections. The solder joints and grounds all tested good. Continuity from the board connections to the filter caps, pots, and tube mounts all tested good. I then started re-checking individual components.
    I discovered a couple of resistors that were not passing current. I replaced them and retested from the beginning. Everything checked out. I adjusted the power tube bias and plugged into a 2x12 cab and tried a guitar. It sounded great.

    Here is the chassis after the trouble shooting and rework.

    reworked chassis.jpg

    I mounted the chassis in the cabinet and closed up the back.

    chassis mounted.jpg

    back attached.jpg

    This is how it looks assembled.

    front panel.jpg

    This has been a very educational and fun project. I will be casting about for similar projects in the future. If I can get my recording gear setup and working, I will try to add some sound clips in the future. In the mean time, this has replaced the Origin 50 in my wet/dry rig.
     
    Gleesonjf, LiteAsh, SacDAve and 9 others like this.
  11. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

    Posts:
    7,662
    Joined:
    Feb 15, 2014
    Location:
    Maine
    Wow, Wolf, that is awesome. Nice job.
     
  12. awasson

    awasson Poster Extraordinaire Gold Supporter

    Age:
    56
    Posts:
    5,680
    Joined:
    Nov 18, 2010
    Location:
    Vancouver
    That’s a really nice looking amplifier. Nice job.
     
  13. Kevin Wolfe

    Kevin Wolfe Tele-Meister

    Age:
    62
    Posts:
    444
    Joined:
    Jun 13, 2017
    Location:
    Lakeland FL
    Nice looking work.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.