Yet another 5E3 Noob Build Issue Troubleshooting

Discussion in 'Shock Brother's DIY Amps' started by hubajube25, Sep 24, 2021.

  1. hubajube25

    hubajube25 TDPRI Member

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    Hello good people of TDPRI.

    Been a long time since popping into this forum via an actual post, but I lurk and benefit from everyone's insights. Thanks for that.

    So, I've been wanting to do the 5E3 build for a long time and finally willed it to happen. Big thanks to Daytona Dave with Boothill amps for the kit and John Mergilli for the cabinet. Dave has been very patient with my rookie questions but wanted to share my pain with others to selfishly benefit from your collective expertise. I am done now with the build in the sense it is all together, but upon powering it on and starting with Weber's first power on processes, I got issues. I double checked my wiring along with way, but didn't test the continuity until just now. Alas, we learn.

    Firstly, only the 3V 6V6 is glowing along with the pre-amp tubes. Voltages of the red leads from the PTX are at 390. The yellow leads from the PTX at the B+ pin 3 is not measuring anything. I can only think that the flow is being disrupted early in the circuit. Obviously, nothing is happening and I essentially built a really expensive jewel light switch.

    FWIW, I realized late into the build that the two primary schematics I used, Boothill amps document with the kit, and Rob's '5E3 "Deluxe: Amp' had slight differences. More specifically on the OT centertap and the Standby switch. It seems my issues would go beyond this if I am understanding the circuit path.

    Guess my question or help needed is more in general with where I should go from here. I included some pictures of what I put together, but please note I am relatively new on the soldering iron as well, so it will look like it. Basic questions to start:
    • Should I move the center tap of the OTX to the standby switch (revert to Boothill)?
    • Is my white/neutral coming out of the power cord correctly wire nutted to one of the black leads of the PTX?
    • Based on the tube filaments not glowing, is there an point in the circuit that may be the issue?
    • Any feedback on other connections?
    • Other voltage checks I can offer to provide more data for troubleshooting?
    Appreciate any help that can be offered, even if the help is 'put down the iron and take it to a builder.' I will be diving into this weekend.
     

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    Last edited: Sep 24, 2021
  2. Paul G.

    Paul G. Friend of Leo's

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    The red leads are AC. The other voltages are DC, so -- are you measuring them with the meter set correctly?

    The filaments are run from the 6.3 V secondaries from the Power Transformer. These are the green wires coming from the pilot light to pins 2 and 7 on the 6V6. Make sure you have good connections there.

    It's fine where it is.
    Never use wire nuts. The connection is correct, but solder and heat-shrink it for safety. Wire nuts can loosen and leave bare wires floating around your chassis.
    See above paragraph.
    [​IMG]
     
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  3. separateness

    separateness TDPRI Member

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    I've never built one of these but I've built other amps and I know something about troubleshooting. If I am understanding you correctly, you have a power tube which is not warming up and you have no B+ voltage?
    Assuming this is the case, the parsimonious way to go about this is to
    1) With the amp off ensure you have continuity along the both sides of the whole heater string/pilot light circuit. Then with power on, ensure you have 6.3V at the filament pins of the unlit tube. Test on the tube socket itself. I have in the past had bad solder joints in the heater circuit which would not conduct or would do so intermittently. It was the dickens to figure out because it looked solid but the solder needed to be reflowed so that everything cooled together properly. As an aside, I would perhaps suggest working on your filament lead dress but, well, you'll get to that.

    2)find where you do have power supply voltage. You have it (AC) at the output of the power transformer (I think), well do you have your DC B+ at the output of the rectifier? If you do, keep going down the B+ line ensuring you have voltage along the way. If you have voltage at one place, say the output of the Power Tranny but not the next (the output of the rectifier), well then we have a problem with the rectifier. This sort of divide and conquer, follow-the-voltage-and-find-where-you-are-losing-it method is common to troubleshooting electrical/electronics systems of all sorts.

    As far as where you would put a standby on this, I would assume it would be in line directly before the junction of the first filter cap and OT center tap.

    I have never used wire nuts in an amp.
     
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  4. hubajube25

    hubajube25 TDPRI Member

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    Thank you Paul G, seperateness for your insights.

    No wire nuts in amps... Got it. Guess I wired one too many car stereos. I will be changing that one as the first order of business.

    I will go back to double check and reflow my filament lead dress. I know, its pretty bad looking. I had actually considered abandoning the stranded wire in lieu of vintage cloth wire (solid) as I feared the fraying was sloppy and may impact the integrity of the wiring. I still may rewire it, but I thought since I did the work with the stranded, would see if it would be good enough.

    I will also go back over the voltage on both AC and DC sides after confirming I have the right settings. It could quite possible be operator error.

    Attached are a few more photos as the key parts of the wiring may not be as well covered. Thanks again for your help!
     

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  5. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I just noticed the key on the 6V6 tubes do not seem to line up with the sockets. Make sure the tubes are in properly.

    This would account for the 6V6 tube not glowing or conducting.

    Careful, do not break off the keys of the 6V6.

    InkedIMG_0918sockets_LI.jpg
     
    Last edited: Sep 24, 2021
  6. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    It doesn't look like there is an under board ground wire soldered in the center of this turret (6V6 220K grid leak resistors junction).
    Use your meter to check this turret has continuity or low resistance to the ground bus wire. If there is no connection, solder a wire from this turret to the ground side of the middle 22uF filter cap turret. As shown in purple on the picture below. (I know Rob and Dave probably show the connection at the closest filter cap but better practice is to connect it to the ground side of the middle 22uF filter cap. I will explain if needed.)

    InkedIMG_09115e3undone_LI.jpg
     
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  7. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I do not see the under board connection at the turret with the yellow arrows. Make sure it has continuity or low resistance to the turret with the green arrow.

    InkedIMG_09115e3undone_LI3.jpg
     
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  8. TobyZ28

    TobyZ28 Tele-Meister

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    Hi @hubajube25 , congrats on diving in to your first amp! It sounds like you're stuck at a "what should I do now, it doesn't work" point. I would start methodically from the plug in the wall all the through the circuit comparing what you're expected values are against the measured. It looks like you've already started to do this
    • Do you have Current Limiter Setup when your testing? If not, I would make one, yunno to prevent dying and stuff.
    • "The yellow leads from the PTX at the B+ pin 3 is not measuring anything." Measure AC between pins 2 and 8, i think you made a typo and meant 8. If this still measures zero stop, make sure your fuse is not blown and the AMP is actually On (yea i've been there).
    • If it all checks out your PT is bad for the (yellow) 5V lines, which means the rectifier won't work right which means everything down the chain won't work as they won't be getting power, or the right power. It also would explain why your heaters appear to be working (I wasn't clear on which ones were operating correctly or not though) but nothing else is.
    • I think you checked your Red AC HV lines to the rectifier and verified they are OK.
    • If your 5V is ok then check your 6.3V heaters, if they are all working you just need to verify the voltage is within spec
    • If your 6.3 checks out, Now you can start looking at what the rectifier is putting out (DC out pin 8, aka B+1) and then your B+2 and B+3 Voltages.
    If all the above check out your off to a good start, but in your post you mentioned your B+ is showing nothing, so my money is on bullets #2 and 3 being your problem.
     
    Last edited: Sep 24, 2021
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  9. hubajube25

    hubajube25 TDPRI Member

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    Thank you TobyZ28! I thoroughly enjoyed the building process but found moments of small frustration in working with my ham hands/sausage fingers in the sometimes tight quarters of the chassis.

    Appreciate the blown fuse line of thinking. I actually did pull it before you suggested it and I noticed what appeared to be a very thin wire. I thought perhaps the fuse was still intact because of that, but in looking a slow blow fuses online, it appears that it is blown and likely playing a role here.

    Question for you and others. When I brought my amp online for the first time (images of lightning and Frankenstein on a raised metal table) there was some very light sparking right at the pilot light. It appears a small strand of wire was within the two wiring harness areas at the light. Total noob question, would that have blown the fuse? If not, I guess I have bigger problems that need attention before throwing a new one in.
     
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  10. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Possibly, but the 6V6 being inserted incorrectly would have the wrong pins connect with a good chance of creating all kinds of havoc.
     
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  11. hubajube25

    hubajube25 TDPRI Member

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    Thanks... Yeah, I can't believe I did something so dumb. I suppose this thread will become an example case study in 'here's why you don't do this' for others to learn from (or simply point and laugh... lol)
     
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  12. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    You learn more this way.

    It happens to the best of us. You will see a lot of *don't ask me how I know.* comments. Been there done that. hah.

    You will be the expert soon.;)
     
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  13. dan40

    dan40 Friend of Leo's

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    Check your fuse with your meter set to continuity. A good fuse should read just a few ohms on the meter. A bad fuse will show open or "OL" on most meters. When checking your voltages throughout the circuit, always be sure your meter is set to the correct voltage. All of your incoming power, the green and yellow filament wires and the two red wires leading from the PT to the rectifier socket will be an "AC" voltage. All of your other voltage checks from pin 8 of the rectifier through the B+ rail and your plate voltages on the sockets will be read as a "DC" voltage.
     
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  14. hubajube25

    hubajube25 TDPRI Member

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    Thank you! Will be doing that this evening and that is helpful for the novice amp builder. Much appreciated.
     
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  15. hubajube25

    hubajube25 TDPRI Member

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    In the meantime, I reseated the erroneously crammed 6V6 properly into the socket and I now have 4 of 5 filaments glowing. I will be checking the fuse and replacing it if is bad. If it failed, hope to be able to source one from the local hardware store. Otherwise I will be placing an online order and waiting a few more days...

    I also included a picture of the pilot light wiring where I mentioned sparking above. I am going to resolder the inside of the two attached connections as the stranded wire threads and solder glob are 'spilling out' from the intended connection.
     

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  16. TobyZ28

    TobyZ28 Tele-Meister

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    Sounds like your getting closer... You did mention 4/5 tubes are glowing now, which means your fuse must be fine. IF the fuse is bad nothing should work at all in the amp, unless I'm totally misunderstanding something :confused:. Side note: I've personally had a slow blow fuse look totally fine but was actually blown - check with a multimeter as mentioned above :)

    The 5VAC not getting to your Rectifier (V5) explains why its not not warming up, and also explains why you have no voltage at B+. My money is on that! A strand of wire can cause a fuse to blow, but unless its a pretty thick strand (and/or very short) I would imagine a single strand would heat up very quickly and burn itself out before a slow blow goes off.
     
  17. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Since the 6V6 was in the socket wrong, might the rectifier be installed wrong as well? That could explain the rectifier not glowing.

    After you check the rectifier tube position, take the rectifier and the 6V6 tubes out and measure for VAC with your red probe one pin 2 of the rectifier socket and the black probe on pin8. It should read a little over 5 volts AC.

    If there is 5 VAC there, then install the rectifier and check for high voltage DC from rectifier pin8 to ground. You can use alligator clips to do this hands free. Use all high voltage protocols when checking voltages. whether the amp is *on* or *off*.)

    When the tubes are not functioning the large caps will hold a charge. The charge can knock you on your butt even if the amp is *off*.
     
    Last edited: Sep 24, 2021
  18. wangdaning

    wangdaning Tele-Meister

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    You really should not have started it up with all tubes. Look for @robrob 's startup procedure. First no tubes, then rectifier only...This will help you identify the problem. If the rectifier is not putting out power no need to sacrifice the other tubes. First sort that, then move on.
     
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  19. hubajube25

    hubajube25 TDPRI Member

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    oh.... my... goodness. Is 2 misplaced tubes a first time for TDPRI Shock Brothers forum? lol.... Yes, I did it again. I had the rectifier in wrong. Upon reinstalling the tube, I not only have all five tubes glowing, but I am getting sweet sounds out of my normal and bright #1's. My #2's are not working though. My first thought is I went way too crazy trying to bend the jack arm away from the ground and turret board. The 1/4" cable does not go in all the way which is not a good thing. Perhaps that is it.

    Yes, the fuse is still intact. I did a continuity test ahead of the rest and while my meter didn't give me an read in terms of a measurement, it provided an audible sound if there is a signal under 50. I also forgot I removed it when I made the below repairs and thought I screwed it up again as it wasn't powering on. Then I realized I forgot to put the fuse back in.

    I also nuked the wire nut in favor of the solder/heat shrink solution and looks much better. I am sure I will be able to hear the tonal difference as well, lol.

    I checked continuity on the suggestions above and got a good signal on all but the below that the kind poster of Lowerleftcoast offered above (reposted the picture). Unfortunately, I didn't take a picture of the back of my board (another key learning) but I did double check and counted the connections before installing which all checked out. That said, it doesn't mean it is there and/or if it is a bad solder joint.

    So, key learnings thus far.
    1. Don't be a jackhole and cram the tubes in there thinking that 'they may just be tight fit' as previously read, even while thinking I had the key lined up.
    2. Take a picture of the back of the board before install just to have a reference point if necessary.
    3. Be careful when bending the input jack hardware
    4. Great community of people on this forum that continue to impress
     

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  20. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    If in the above photo (post 19) were not making contact there would be no sound. We know there is a connection there because it is making sound.
     
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