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New 5E3 Build

Discussion in 'Shock Brother's DIY Amps' started by Lavely, Dec 22, 2020.

  1. mrfitz98

    mrfitz98 Tele-Meister Silver Supporter

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    Sounds to me like a cold solder joint somewhere in the output side.
     
  2. Muzzy

    Muzzy TDPRI Member

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    Bad/cold solder joints can cause that as they heat up and expand. You need to use more heat and solder. Are you using 60/40 solder? It looks like your soldering iron isn't hot enough.
     
  3. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I assume the V3 pin3 is a typo. Is it 298?

    The EH are biased cooler than the TS but they are still highish running about 134%PD.

    The B+ seems wrong. Usually the VAC voltage is lower than the rectified voltage. For instance a 330-0-330 PT, after rectified with a 5Y3, will deliver 370VDC B+.

    A 12ax7 will run higher voltages than a 12ay7 so V1 pin1 and pin6 will be higher than the *proper* voltage.

    The starved for voltage description gives us the idea of bad solder joints. If the EH are redplating odd sounds can happen from that too.

    The rectifier solder joints should be reflowed. There seems to be a problem there. I would think more connections than that need attention though. Make sure both Center Taps have good connections. Make sure the grounds for the filter caps/ground bus are good.

    What rectifier tube are you using?
     
  4. D'tar

    D'tar Friend of Leo's

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    Just an observation... V3,V4 pin 5 control grid should not have high voltage DC. your proper column is incorrect. The voltage should be on pin 4 the screen grid connection like your actual reading.


    upload_2021-1-25_9-59-16.png


    Did you do this? confirm the 250 ohm cathode resistor and measure also from each power tube pin 8 to ground... It should be equal to the cathode resistor value. I agree with some of your joints needing attention. You also may want to shorten some of the "tails" left on the stripped wire ends. pull the wire insulation up close to the solder terminal, make a mechanical connection then apply heat and solder. Trim off excess wires.
     
    Last edited: Jan 25, 2021
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  5. Lavely

    Lavely TDPRI Member

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    Back at it. In response to: “Do you have the *measured* resistance of the 6V6 250 Ohm cathode resistor? It is the large dark gray resistor next to the filter cap.”. The answer is that it measures at 248, so seems fine.

    but, each power tube pin 8 to ground is at 38 VDC - same reason on the tube side of the resistor, if that was what was meant?

    Rectifier tube is NOS JAN-CNU.

    I’m going to redo some solder joints and retake measurements.
     
  6. Lavely

    Lavely TDPRI Member

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    NEW problems now...I redid a bunch of solder connections to deal with the idea of a "cold solder" connection. Wicked away the old solder, reconnected the wires, re-soldered the connections (hopefully better this time). Also, shortened some wires and in many cases cut and restripped a much smaller length of wire, so there is much less "exposed wire" now. I'll get full pics up soon. In the meantime, I was going to do the whole re-start and measure voltages to see if the work helped, and now not even my pilot light comes on. Bummer. So, before I plow into the voltages again, gotta get the juice moving!



    Here's that end of the chassis and two separate angle shots of the recto socket. Why isn't my pilot light getting juice?



    [​IMG]Untitled by joelavely, on Flickr





    [​IMG]Untitled by joelavely, on Flickr





    [​IMG]Untitled by joelavely, on Flickr
     
  7. jmp81sc

    jmp81sc Tele-Meister

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    Your Pilot light and tube heater voltage comes from the twisted green wires directly for the power transformer. So either a bad solder joint to the pilot light, a burned out bulb or your output transformer is not putting out the heater supply voltage. Or you are not getting 120V AC to the power transformer.

    I would make sure your main power and fuse are good, then measure the green heater wires voltage to check the transformer is working properly, then the bulb and soldering.

    BTW you probably should solder/crimp a terminal to your mains ground wire to secure it to the chassis, rather than wrapping the bare wire under the mounting screw.

    I know that electricians do it this way with house wiring, but that is solid 12 or 14 gauge wire, not the smaller twisted wire in guitar amps.

    Good Luck
    John
     
  8. Lavely

    Lavely TDPRI Member

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    Well, it looks like it was a blown fuse! Crazy. After replacing the fuse, I fired back up one stage at a time, with lightbulb limiter, etc. Ultimately, it works fine! Must have been bad soldering, as I redid much of the tube side of the chassis, also a lot of the board connections.

    Of course, the best part was plugging in a guitar - wow! Damn thing roars!!! A few things I still need to clean up, including re-wiring some of the control panel side of the chassis, but it works!! Very cool to get a little reward after struggling a bit. New voltage chart below...if anyone has corrections or additions to the "Proper" columns, please let me know and I'll add them.


    [​IMG]Screenshot (6) by joelavely, on Flickr
     
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  9. D'tar

    D'tar Friend of Leo's

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    Sweet! Congrats! It's a great feeling right!!! Enjoy!

    Your voltages look great!
     
  10. jmp81sc

    jmp81sc Tele-Meister

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    Nice work, glad you got it sorted.
     
  11. Lavely

    Lavely TDPRI Member

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    I appreciate deeply the help on this Board!!!!!
     
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  12. Lavely

    Lavely TDPRI Member

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    I went through to clean up some long wiring, re-do some solder joints, replace some jumpers with too much exposed wire. The result - V1 voltages are now screwy (the rest of the tubes and B+ are in the right ranges)! Pins 1 & 6 are now 280VDC, pins 3 & 8 are now 5VDC. I do have a 12AX7 in V1, FWIW. Pics below, of the preamp section wiring. Any specific thoughts? Voltages were good before my rewiring, just not sure WHICH rewire would have caused the voltage jump.





    [​IMG]Untitled by joelavely, on Flickr



    [​IMG]Untitled by joelavely, on Flickr



    [​IMG]Untitled by joelavely, on Flickr
     
    Last edited: Jan 31, 2021
  13. D'tar

    D'tar Friend of Leo's

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    Do you have a jumper wire from V1p3 to V1p8? Also make sure V1p4 and 5 are joined together.
     
  14. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    ??? I don't understand how the V1 pins can be higher than B+3. Check the B+ numbers.

    To compare numbers, my 5E3 with a 12ax7 in V1:
    Pin1 166
    Pin6 163
    Pin3/8 1.32

    B+3 247

    When using a 12AY7 the Pin1 Pin6 voltages are less.
     
  15. Lavely

    Lavely TDPRI Member

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    @D’tar - yes, V1 pins 3-8 and 4-5 are jumpered

    @Lowerleftcoast - the chart above is no longer valid with the resoldering. Now:

    B+1=384
    B+2=320
    B+3=280

    With these readings, V1 pins 1 & 6 read 276VDC, pin 3 & 8 still around 5VDC.
     
  16. D'tar

    D'tar Friend of Leo's

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    Can you ohm V1p8 & V1p3 to ground with amp off/unplugged caps drained

    Also
    V1p1 to B+3
    V1p6 to B+3
     
  17. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    V1 is not conducting properly.
     
  18. Lavely

    Lavely TDPRI Member

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    V1 - both pin 3 and pin 8 to ground read 0.L on the Ohm setting - I assume some sort of error message?

    b+3 to v1 pins 1 & 6 both read 101 Kohms
     
  19. D'tar

    D'tar Friend of Leo's

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    OL mean you do not have proper path from V1p3/8 through the 820 ohm to the ground
     
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  20. D'tar

    D'tar Friend of Leo's

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    Reflow connections and or replace broken wire
     
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