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.

5E3 Mods gone wrong?

Discussion in 'Shock Brother's DIY Amps' started by James Knox, Sep 8, 2020.

  1. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    So I’ve gone back in to the 5E3 I built in July. It sounded really good, just really bassy and farty, lol. I know it is what it is!

    Changed the Bright Channel .1 Coupling cap to .022. Better! Changed the Normal channel .1 coupling cap to .0047 cuz I’m thinking of doing the Cascading Channel mod Rob suggests. Less flub, less farting... I like it.

    Tried the Pre PI Master Volume. Didn’t really care for it, so I took it out.

    Amp still sounds good.

    Then I made a classic mistake. Made a bunch of changes without checking along the way. :mad: Rookie lesson learned, lol.

    I read that I could still smooth out overdrive tone and keep distortion sweet by adding a 470k grid stopper to pin 7. I like smooth and sweet. Did it!

    Added the 3 way NFB mod. Cool. Got the squeal, changed the OT leads.

    Added 470R Screen Resistors to both 6V6s. Good enough for the Edge, good enough for me!

    Now, all excited to play some EQed creamy, smooth, sweet distorted Rock Riffs I plugged in and turned on. Ouch... harsh. nasty. Distortion like a really bad SS amp. :(

    I read through Robs Troubleshooting guide and learned that bad sounding audio is usually a bag connection or bad component. So.... I triple checked the wiring, the layout, resistor values. I checked all the voltages (B+, tube pins, etc.), all good. I reflowed all solder joints and tug tested every one. All, A-OK. I continuity checked all the “behind the board” connections thinking maybe my reheating the turrets knocked something loose.

    I notice that if I place the 3way switch on the 56k setting every note strummed/played creates a horrific harsh buzzy aweful distortion. I thought that was supposed to be the cleanest, highest headroom position.

    Could my 3 way switch be bad?

    Ive checked everything I can think of and could use some ideas. Thanks so much. Here are some pics...

    A6003CE1-0536-44BA-81E3-C99768349CCF.jpeg DC87A414-350E-4547-A53B-757DBDB013C4.jpeg F15EC31E-F473-4569-B1B9-AC910F46B1B5.jpeg 3FCEA186-79D6-41AB-A510-E08DFF7D3D42.jpeg
     
    Last edited: Sep 8, 2020
  2. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

    Posts:
    3,002
    Joined:
    Apr 30, 2016
    Location:
    Crawfordville, FL
    My guess is, where you did the NFB mod, your cathode bypass cap is connected, but not the cathode resistor.
     
    James Knox and tubegeek like this.
  3. Hachiko

    Hachiko TDPRI Member

    Posts:
    6
    Joined:
    Sep 8, 2020
    Location:
    USA
    Phrygian77 has it right, the way you have it, you have the cathode floating. You only want the switch to change between: bypass cap without NFB or no bypass cap with NFB.
     
    Last edited: Sep 8, 2020
    James Knox and Phrygian77 like this.
  4. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

    Posts:
    3,002
    Joined:
    Apr 30, 2016
    Location:
    Crawfordville, FL
    I inadvertently fired up one of my Vibro Champ builds with the output tube cathode resistor disconnected, because I was testing the bias and tone with different values. That is a pretty God-awful sound.
     
    Last edited: Sep 8, 2020
    jsnwhite619 likes this.
  5. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

    Posts:
    3,002
    Joined:
    Apr 30, 2016
    Location:
    Crawfordville, FL
    Okay, looking at it closer, now I'm thinking maybe something is wrong with the cathode resistor. I can't make out the color codes. Are you sure it's the correct value?
     
  6. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    ahhhh...

    right there in front of me!
     
  7. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Yep. That is NOT smooth, creamy distortion, lol.
     
  8. jtcnj

    jtcnj Tele-Holic

    Age:
    57
    Posts:
    599
    Joined:
    Feb 2, 2015
    Location:
    N.J. USA
    I dont think this is the case, if the nfb switch is either a on-on or on-off-on it looks like the yellow wire is continuous on the center pole of the switch to the cathode resistor, so it would never be switched out (unless the switch was overheated and melted the innards and it failed, dont ask me how I know this).
    +1 on checking the cathode resistor value as well and the voltage across it.

    EDIT: the 56k nfb switch position should be the lowest gain.
    I have misread switch position myself before so I will mention this: remember the toggle will be pointed away from the active contact position.
    If you point the toggle toward the nfb resistor you are in the stock cathode resistor + bypass cap position.
     
    Last edited: Sep 8, 2020
  9. Commodore 64

    Commodore 64 Friend of Leo's

    Age:
    45
    Posts:
    4,261
    Joined:
    Mar 1, 2010
    Location:
    Kent, OH
    I let someone borrow this pretty standard 5E3 build (on a UPCB) with MV. It came back like this: [​IMG]

    With an EF86 switchable in parallel or cascade to V2a, the NFB bods, A James tonestack, A VVR and some other standalone effects loop BS that I took out.

    Rocks pretty F'n hard though. Just never wanna troubleshoot it.
     
  10. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Ok, I rewired the cathode resistor/capacitor. Still sounds horrific!

    This is how it’s supposed to be and now wired this way...

    17E8E69D-CA38-4041-B021-C5CB046F16F0.png
     
  11. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Yes, I was suspecting the switch, so I did a continuity check on all 3 lugs. It seems right.

    #stumped
     
  12. jtcnj

    jtcnj Tele-Holic

    Age:
    57
    Posts:
    599
    Joined:
    Feb 2, 2015
    Location:
    N.J. USA
    What did you change?
    pic #2 in post #1 looks like that except for how the wire is routed and the orientation of the switch.
     
  13. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    That is some “mad scientist” stuff right there!
     
  14. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    I ran the 1.5k resistor from turret to turret. Hung a new Cap from the top turret. Attached the blk wire to the Cap and the yel wire to the bottom turret.

    AEB9CAFD-FC59-4AB2-B7C3-CB24E34BD5C0.jpeg
     
    Last edited: Sep 8, 2020
  15. Commodore 64

    Commodore 64 Friend of Leo's

    Age:
    45
    Posts:
    4,261
    Joined:
    Mar 1, 2010
    Location:
    Kent, OH
    Ironically, it started out as one of the best examples of lead dress I had ever done, LOL.
     
  16. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Yeah, it starts out all beautiful and clean and straight and THEN we start foolin’ round with Mods, etc. :lol:
     
  17. Commodore 64

    Commodore 64 Friend of Leo's

    Age:
    45
    Posts:
    4,261
    Joined:
    Mar 1, 2010
    Location:
    Kent, OH
    Yeah, Man. The dude was COAX CRAZY. I gave him several feet of it, and boy he used it.
     
  18. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,251
    Joined:
    Dec 30, 2019
    Location:
    california
    InkedEdge_Deluxe_Mods_LI.jpg

    Hey! Where did you put this wire? You got no Edge.

    I haven't found the the odd distortion yet... Looking.
     
  19. jtcnj

    jtcnj Tele-Holic

    Age:
    57
    Posts:
    599
    Joined:
    Feb 2, 2015
    Location:
    N.J. USA
    The layout is changed but circuit wise I think everything is the same.

    And it does look like your screen wires need to be moved to pin#1 as in post #18.
    this wont be the fix but the screen resistors are not in the circuit.
     
    Last edited: Sep 8, 2020
  20. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    932
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Its the blue/white wore that runs from pin 4 of V3 to pin 4 of V4. I noticed that the EDGE Mod layout went from pin 1 of V3 to pin 1 of V4 but I built I from a Boothill Kit that showed wiring the other way. Does it matter if they are connected at pin 1 or pin 4?

    916AF659-1366-4AC9-AA75-FE5CE02AEEF9.jpeg
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.