5E3 Tweed Build - Normal Channel Not Working

Discussion in 'Amp Tech Center' started by HookedOnTubeAmps, May 20, 2019.

  1. HookedOnTubeAmps

    HookedOnTubeAmps TDPRI Member

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    HELP!!! [​IMG] [​IMG]


    I finished a 5E3 Tweed Deluxe build a few weeks ago, and I'm getting nothing from the Normal channel – dead silence, except for a little amp noise through the speaker – from both the Hi & Lo inputs. When I turn both of the volumes up and down, the little bit of speaker hiss gets louder and quieter, but I get nothing from the jacks/guitar. However, I'm getting some very sweet and awesome tone from both inputs of the Bright channel. I have gone over every single wire, connection, and solder joint, traced wiring, done continuity tests to make sure wires are starting and ending where they should, and to check for proper and improper grounding, and that includes the tube sockets. At first, I thought it was the coupling cap from V1 (normal channel side), so I removed it, and measured the capacitance . . . it didn't have any. I replaced it with a new cap (measured it first), fired it up again, and the same thing – silence. I removed the same cap again, and tested it, and it tested just fine, so I soldered it back into place, fired it up again, and once again, the same thing – silence. Could both input jacks be bad? I did continuity tests on both Normal channel jacks, and everything tested fine. Since they're passive devices, there's not much voltage to measure. Both volume pots work with the Bright channel – the Bright volume goes loud and soft, and the Normal volume cuts out the Bright volume when turned all the way up – so I don't believe it's a bad Normal channel volume pot, because I tested it's resistance from 0 ohms to 1M ohms, and tested ground as well, and it tested good (I could be wrong though). I swapped the tubes back and forth between V1 and V2, tried two more tubes in V1, and still nothing. I went through and measured all the tube and B+ voltages, and I've attached a pic of the measured voltages. I did the "chop-stick" test, and poked around with an orange stick, but didn't find any loose connections, or find any connections that snapped-crackled-or-popped (yes, I did keep one hand in my pocket at all times).

    I'm at a loss. Is there any way to test the signal within the circuit, to find where the signal is being dropped? I've been through every troubleshooting manual I can find, and searched the internet, but nothing has helped. I've also attached pics of the wiring, a layout of how I wired the input jacks, and the layout I used for the build (I did change it from non-shielded to shielded wiring from jacks to V1). Am I overlooking something? Any help would be greatly appreciated . . . thanks in advance.

    Limited to 10 pics, so additional pics are on next post . . .

    Pic 1.jpg
    Pic 2.jpg Pic 3.jpg Pic 4.jpg Pic 5.jpg Pic 6.jpg Pic 7.jpg Pic 8.jpg Pic 9.jpg Pic 10.jpg
     
  2. HookedOnTubeAmps

    HookedOnTubeAmps TDPRI Member

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    Here's the remaining pics . . .

    5E3 Deluxe Layout Used.jpg Input Jacks Wiring.jpg Voltages.jpg
     
  3. Nickfl

    Nickfl Tele-Afflicted

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    My guess would be a problem at the input jack wiring, it sounds like everything is fine after V1. I know you said you already checked it, but check it again. Make sure that the shorting switches are actually opening up when you insert a cord. While you are at it, test the resistance to ground from the tip of a guitar cable inserted into the bad channel, hi should be 1m, low should be about 136K. If you have no resistance you have a short, check to see if any of the grounded leads around those jacks are touching something they shouldn't be, also check to see if the shielding on either end of the shielded lead to V1 is making contact with the signal wire at the cut ends.
     
  4. Preacher

    Preacher Friend of Leo's

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    I agree with what @Nickfl said.

    I had a slight hisss and hummm and figured it was in the jack wiring. Rewired this weekend, redid all the grounds and it is hum and hiss free.

    It could be one bad solder connection or a stray wire grounding everything out.
     
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  5. philosofriend

    philosofriend Tele-Holic

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    To trace the signal in the circuit the most common way is with an oscilloscope. I wish I still had mine.

    (After you do the tip to ground test like Nickfl described): Plug a guitar cord in either normal input jack. from the tip of the other end of the guitar cord to the grid connection in v1 should read about 68k or 34k ohms depending on which normal jack you picked. I would pull out the tube and do this test right down the hole that that pin of the tube goes into, who knows, maybe the tube socket is defective (not likely).

    When you put a plug into the input jacks it is supposed to break the connection between the tip and the third (non-ground) jack terminal. If that connection is not being broken it would give the problem you describe. Also, even one little stray hair of copper wire between any metal in the jack-to-grid section would kill the sound. I use a magnifier and a bright light to make sure no wire has a strand hanging out.

    With the other channel turned down, does turning the normal channel all the way up give a bit of hum or hiss sound out the speaker? That would pretty much indicate that the plate of v1 is hooked up right.
    If so, then the problem should be between the input jack and the grid of v1. Since that part of the circuit is totally passive you could unplug the amp, remove v! and safely signal trace with the help of a working guitar amp. Plug your guitar into the ailing amp. Take a guitar cord from the working amp, run a jumper from the sleeve to the ground of the 5e3. Then a wire from tip will be your probe to use on every connection between the jack and the grid. You ought to be able to put that wire into the grid hole in the tube socket and hear your guitar in the working amp.
     
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  6. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Step 1 in amp troubleshooting - voltage chart of V1. See what that tube is doing.

    Step 2 - signal tracing, for such a small area it wouldn't take long. You can google how to make a signal tracer, but all you need is an audio source (radio, cd player, phone - just something to plug into the amp) and old guitar cable you don't feel bad about chopping one end off, and a 600V capacitor.
     
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  7. philosofriend

    philosofriend Tele-Holic

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    It could also be a cold solder joint or defective socket to the (normal) cathode of v1. You should measure zero ohms between pins 3 and 8 (the two cathodes) in the socket.
     
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  8. HookedOnTubeAmps

    HookedOnTubeAmps TDPRI Member

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    First, I want to thank everyone who put in their $0.02 cents worth – actually it was all much more valuable than that, because I wouldn't have found the problem without everyone's help. But as a result, I now have a greater breadth and depth of knowledge about building and trouble-shooting amps, so again thanks. Also, I want to apologize for not responding to everyone's posts/suggestions sooner. It's been a crazy week at work (I'm a teacher, and it's the end of the school year), and so didn't get a chance to try anything until today, and I've been working on it for the last couple of hours, going through everyone's suggestions. The result is . . .

    PROBLEM SOLVED!!!! :D

    From the suggestions on the Telecaster Guitar Forum, I again measured voltages, resistance, and continuity at all the point suggested, I couldn't find anything wrong. I measured resistances like Nickfl, Preacher and philosofriend suggested, and everything measured really good – within the ranges they mentioned. As philo also suggested, I again checked speaker response with nothing plugged in, and the slight speaker-hiss went up and down when the volume knobs were turned up and down. I also removed V1 and measured the resistance between the inside of the pin sockets of p3 & p8, and got 0.2 ohms. All still good, and thanks to corliss1, I now have my own home-brewed signal tracer.

    From the Les Paul Forum, as suggested – thanks Case24, Wrench66, and Pappy58 – I double checked the heater connections and turned out the lights to make sure V1 was heating up properly. Tubes looked good, and both triodes were glowing nicely. I checked continuity of the center conductor of the shielded cable, and continuity through pin 2 of V1's tube socket. It was also suggested to check if the normal channel's shielded wire center connector was shorting to ground. I did, and it checked fine. So for everything is checking properly . . . CRAP!!!! . . . (not what I really said).

    On The Gear Page Forum and the Hoffman Amplifiers Forum – thanks HotBluePlates, oldhousescott, Rockinrob86, zenas, VaughnC, Winnie Thomas, 66 Kicks, sluckey, and PRR for your input – I tried the suggestions of measuring voltage with the guitar plugged it at the normal channel plate – voltage was fine. Triple-checked the input wiring, and again everything looks good. Checked the pots again – everything checked out, and amp sound/hiss through the speaker went up and as it should with the volume pots turned up and down. Also, I checked all grounding wires and looked for cross-contact, and again everything looked and tested just fine. Unfortunately, I don't have a signal generator or oscilloscope to do the other tests; and I didn't get to the suggestion of using a second amp (suggested by a couple of posters in other forums as well).

    I was going to try sluckey's suggestion of swapping the normal and bright inputs on V1, and I remembered the comment from "The Ballzz" on the Les Paul Forum, " Why the shielded cable? I agree it's the most probable cause, and not needed at all. I've built a half dozen tweed kits and never used it." This was my first build with shielded cable, so I decided to remove it from the normal channel and replace it with plain old cloth push-back wire when I did the V1 swap between normal and bright. Just before I pulled it out, I tested the center conductor to ground one more time before removing it, and voilà – the center conductor was grounding out!!! I pulled out the shielded cable, and I found a single tiny strand of cable wire with a little solder at the bottom of Pin 2. It was going over towards Pin 1, and I didn't see it because the shielded cable was blocking it!!! Apparently, every time I took measurements with V1 out, there was no grounding. But when I plugged the tube in, the sockets would move and the little strand would make contact between Pin 3 and Pin 1, grounding it out.

    Long story short (too late for that I guess), I cleaned off all the solder and wire strands from Pin 2's solder connector, soldered in the non-shielded wire between V1 and the normal channel jacks, and the problem was solved. Along the way I learned a few new things, got a new piece of test equipment for my bench – you can never have too many tools (unless you ask my wife) – and best of all, I have an awesome tone machine with the 5E3. It sounds amazing, and will now be played and played until my wife complains, at which time I'll turn it down and keep playing . . . now for my next amp, I'm going to build a British-style 18 watt 1 x 12 with . . .

    Again THANKS TO ALL!!!
     
  9. Paul G.

    Paul G. Friend of Leo's

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    Don't feel bad. That exact thing happened to me on my first build 15 years ago. It took me a couple of days to find that one fine strand.

    More recently, one of my 18-watters gave me crackling when plugging and unplugging into the normal channel. Turned out to be caused by the same sort of thing, intermittent this time.
     
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  10. Wally

    Wally Telefied Ad Free Member

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    Kudos on finding the problem. Fwiw, the fact that the Normal channel volume control raised the white noise at the speaker indicated that your problem was in the input signal to that tube. And...making a voltage chart pull have also clued one into that since the POP hard at the plates of V1 would have been the loudest pops heard in the circuit. That would have been another indicator that V1 was conducting current. The increase in the volume of the pops to be heard when taking voltage measurements starting at the power tube plates and moving back toward the inputs is one of the oldest diagnostic tests...and it is still viable.
     
  11. HookedOnTubeAmps

    HookedOnTubeAmps TDPRI Member

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    Great info, thanks. I'll remember that for next time I'm trouble shooting . . . again, another tool for in the box.
     
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