Newbie 5f1 Build

Discussion in 'Shock Brother's DIY Amps' started by MD57, Apr 3, 2018.

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  1. MD57

    MD57 TDPRI Member

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    20180512_141540.jpg 20180512_141550.jpg 20180512_141612.jpg 20180512_141622.jpg 20180512_141634.jpg 20180512_141648.jpg 20180512_141709.jpg 20180512_141716.jpg 20180512_141720.jpg back of board.jpg Thanks to all who posted. I moved the power tube's cathode resistor to pin 8 and connected the shorting contact tab (center) to the ground tab on the speaker jack as suggested. Also, OT is classic Tone 40-18031 and the indicator light is on. Still no sound. Is the power tube supposed to glow/get warm because it doesn't.

    Included the back of the board in the attached pics

    20180512_141540.jpg 20180512_141540.jpg 20180512_141550.jpg
     
  2. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    So what are we looking for to make the power tube glow? We need AC voltage at those pin where the heaters connect to 2 and 7. Do we have that? Does the 12ax7 glow?
     
  3. clintj

    clintj Friend of Leo's

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    Pull all the tubes and look for AC voltage in each of the following spots, with one meter lead clipped to the chassis:

    12AX7 socket (V1), pins 4, 5, and 9.
    6V6 socket, pins 2 and 7.
    Indicator lamp, both solder lugs.

    You should find about 3.15VAC at each point, give or take a few percent. There's an open circuit somewhere in the heaters, let's find out where.
     
  4. D'tar

    D'tar Friend of Leo's

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    Whats going on here? Looks like three terminals? This looks fishy to me. Should be four wires and only two connection points?

    Screenshot_2018-05-12-16-28-01.png
     
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  5. jimgchord

    jimgchord Tele-Afflicted

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    Also, you will have to change that ot wiring. The blue lead goes to the board and the red or brown goes to the tube
     
  6. clintj

    clintj Friend of Leo's

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    I'd suggest leave it be for now; there's a 50/50 chance it might be the right polarity as is. If the amp squeals the first time you get sound, then definitely switch them as above.
     
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  7. MD57

    MD57 TDPRI Member

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    Pulled the tubes and tested 12AX7 socket (V1), pins 4, 5, and 9.
    6V6 socket, pins 2 and 7.
    Indicator lamp, both solder lugs.
    all points above indicate 3.6v AC

    The reason there are 3 solder points on the pilot light is that 2 of them had continuity and it was easier to solder one wire to each
     
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  8. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    3.6V is right on the money.

    Put in just the 12ax7. Does that tube glow?

    If so, do you have a different 6v6 you could try?
     
  9. MD57

    MD57 TDPRI Member

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    corliss1, I put in only the 12ax7 and it did not glow or get warm. I tested the voltage with the tube in and it was 3.6 v ac at the 4, 5, and 9 tabs. I do not have another 6v6 but could pick one up tonight at guitar center. I will be traveling for a couple weeks starting late morning tomorrow.
     
  10. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Nah - if neither the 6v6 nor the 12ax7 glows, something else is up. You have the correct voltage though, so that's odd. I'd go through and start triple checking everything.
     
  11. clintj

    clintj Friend of Leo's

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    Pop one tube in, either one, and check heater voltage again. Your wiring may pass normal voltage unloaded, but drop out once it has to actually supply current.
     
  12. MD57

    MD57 TDPRI Member

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    Success! Thanks to all. This is a lot more fun when you get sound. I moved the wire on the pilot to the same tab as the PT output (shout out to D'tar) and then when I got glowing tubes and a squeal sound changed the polarity on the OT (shout out to Jimgchord and Clintj. Also, thanks to corliss1 and hackworth1. There is more hum than I would like but the tone is awesome. Will address the hum issue later.
     
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