5e3 expert opinions

Discussion in 'Glowing Bottle Tube Amp Forum' started by JamesAM, May 13, 2020.

  1. David Barnett

    David Barnett Doctor of Teleocity

    Age:
    63
    Posts:
    12,803
    Joined:
    Mar 17, 2003
    Location:
    The Far-Flung Isles of Langerhans
    Could it be that the dirty ground is not properly separated from the preamp ground?



    (dirty ground - the current loop including the power transformer, rectifier, and 1st stage of filtration)

    (not to be confused with dirty pillows)
     
    tubegeek and JamesAM like this.
  2. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    that’s what I think- it must be a combination of that plus single wire heater noise. When I rewire I might ground the first two filter caps at a star ground like in robrob’s layout and get them off the brass plate. I figure a new ground, removing the HT standby switch to the negative terminal of the second filter, and installing an artificial center tap will get me where I need to be.
     
  3. tubegeek

    tubegeek Tele-Afflicted

    Age:
    59
    Posts:
    1,743
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    You've been sleeping on the ground so much that you are making that mistake?
     
  4. David Barnett

    David Barnett Doctor of Teleocity

    Age:
    63
    Posts:
    12,803
    Joined:
    Mar 17, 2003
    Location:
    The Far-Flung Isles of Langerhans
    [​IMG]
     
  5. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,189
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Good for you. TBH, I was feeling like if you ever did fix your buzz it would still just mean you’d finally found the pig's lips on which to put lipstick. That amp is ill, and not in the good way.

    What layout are you gonna use? The board itself is pretty much still what Fender drew, but their grounds, heaters, and power wiring are somewhere between suboptimal and dangerous.

    FWIW, as you likely know, Rob's 'unmodded' 5e3 layout is hard to beat. Tho even there, like @muchxs and Merlin, I omit the standby switch, and you’ll still have to decide how to do your artificial heater CT, and a few other things.

    [​IMG]
     
    JamesAM likes this.
  6. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    I’m right with you. I’ll be using this exact layout without a standby (I’ll put a dummy switch in there for now), but I will likely keep the brass plate for grounding the preamp as opposed to wiring in a buss and see where that gets me. I’ll move the power ground to a chassis bolt like rob has here- I figure that will give me enough separation to quiet things down. What do you think?

    the cab is super nice, the speaker is from either 1952 or 1962 and is perfect, and the chassis is sturdy.

    i went with mallorys for the coupling caps as opposed to the orange drops. I figure if I don’t like them, I’ll just put the orange drops back in.

    the last thing is the power transformer- it’s safe to put a lineman’s splice into the hv tap lead, right? It’s not long enough to reach the second filter cap. I’d prefer not buying a new transformer, but don’t want to burn the house down.
     
  7. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,189
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    What do I think about keeping the brass plate? Ummmm. Some smart people here think that plate may be your problem. It's known to fail when corrosion gets between it and the steel chassis. Soldering your new grounds to it is gonna be a total bear, and re-soldering it to the chassis, at home, almost impossible. A new brass plate can work if done well in a new chassis. Trusting an old one? I think you're saying, "I'm gonna rebuild my whole car -- except for the drivetrain."

    A ground bus sounds complicated, but it can be a chunk of straight wire running across the front of the board held in place by the ground leads coming off the nearby eyelets. Use good solid-core wire (22 will do, but 18, or Romex core, is better) and ground it to an input jack. Look at a bunch of 5e3 builds and you'll see dozens of ways to make it work.

    Mallorys should be great and are sure a lot easier to fit than ODs. Some folks think caps don't alter sound, but among the rest of us, Mallorys rate well.

    Yes, a good lineman's splice can be put into virtually anything. There's a reason it was called the Western Electric splice.

    I really like your idea of re-doing the amp. What'd my dad say? Oh, yeah, "Any job worth doing is worth doing right..." :)
     
    JamesAM likes this.
  8. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    Sounds good. I’ve got some 18awg set aside just for this, so that works. The only reason I was going to reuse the brass plate is because it’s really soldered into the chassis good and will be tough to take out. It’d be a lot easier to use the wires already soldered to the plate and put them back into the new board, but I’ll make it work. As long as I can keep the brass plate on the chassis and still use a preamp buss, I’m good (muchxs said this would be fine, so I’m not too worried about it).

    I wired up the board yesterday and it looks great. Going to go heaters first and wire them old style, under the chassis lip, then put the board in. I’ll let everyone know how it goes.
     
  9. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,189
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Muchxs is right, of course. It isn't the plate sitting in the amp that can cause problems, it's the grounds going through the plate.

    Maybe I'm missing the difficulty you picture rewiring all the grounds -- imagining maps and layouts from words is hard. But I see 3 ground wires from the preamp board, and 2 from pots, to a 'bus wire' that then attaches to an input ground tab. And the power amp ground bus is even simpler; it can be 2 lengths of black wire (or lavender wire, who cares) linking the first two filter caps and the bias ground eyelet. As I say, maybe you see doing more (or less?) than that...
     
    JamesAM likes this.
  10. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    Oh no there’s no difficulty in the buss wire, rob’s layout is super straightforward. I’ve already wired it into the new board - it’s ready for installation into the chassis. Ill solder the end to the ground tab of the input jack, as per rob’s layout and your description above.

    I just worry about creating a ground loop with the plate and the buss and I’m back to square 1 chasing buzz. I keep telling myself as long as I disconnect any connections from the plate to the board, I should be good. I shouldn’t need any insulating/isolating washers for the pots or the jacks, right?
     
  11. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    A tale of two boards. Still need two resistors (ordered extra 22k instead of 220k, whoops) and some jumpers, but we’re getting there- also want to triple check before I solder anything.
    had to drill some new mounting holes in the eyelet board, but it mounted to the chassis just fine (thank goodness).

    I’ll work the heaters later on in the week to enjoy the weather this weekend. Hopefully I’ll have everything ready for the first power on test by the end of next weekend.

    ECE6DC6C-407B-4A3C-842E-19E462982401.jpeg
     
  12. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,189
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    You can't have a ground loop from the plate if it doesn't have any grounds on it. It'll just be a brass decoration inside your chassis with some weird solder blob sculpture on it. It could be made out of plutonium for all the electrons care -- they can't loop there if they don't go there.

    You are taking *all* the grounds off the plate, right?

    OK, good stuff. Your new board already looks 85X better than the old one.

    boards.jpg

    I basically love the improvements you've made. Bear with me on picky details. Since you're chasing noise, d'you know how to test those Mallory caps for outer foil end? If not, lemme know, it's easy and useful to test and orient 'em the quieter direction.

    At this point someone usually points out the bias resistor (far left) gets hot -- bend that cap away from it, or bend the resistor further left. If you have a 10W wire wound, it can't hurt to use that (it'll get less hot or have more surface area) but if you don't, no worries.

    I assume those are under-board wires sticking out of the top eyelets and nearly touching the bus wire? It's good to leave visible tails on top with under-board wires, and it's fine to run a simple bus wire there, but nothing except ground can touch it. The logical direction for those under-board tails is right back over their under-board brothers, which will take them down and left, and I might run the bus wire as far from the eyelets as I can.

    As a resistor-aware guy, I'm into your choice of places (like PI plate) to put CC resistors. If there is CC mojo, and I like to hope there is, good for you. I'm not into the CC in the second dropping (22K) resistor, though. Maybe I'm missing something. Wassup there?

    Small details: You can run black wire (for the insulation) on ground legs that might touch something -- like that arch over the mounting screw. And you don't need the green insulation on the ground that goes up from the right end of the bus -- unless you worry it may bend and touch the chassis. Which I hope is unlikely.

    And it's nice to rotate all your caps so the value is pointing up at the viewer -- although the way they print Mallories with so little ink sometimes, it may not matter. Compulsive folks like me orient all their resistors with that bands in the same order, say L->R and top-to-bottom. 95% OCD, 5% makes 'em easier to read if they're all the same.

    Basically, though, your new board compared to the old one seriously says you chose right to rebuild the amp.
     
    hepular and JamesAM like this.
  13. tubegeek

    tubegeek Tele-Afflicted

    Age:
    59
    Posts:
    1,743
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    You don't know that for sure. There's always a first time for everything.
     
    King Fan likes this.
  14. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    Thanks for the feedback, this is awesome stuff. I’ve already gone ahead and fixed most of the things you mentioned:

    - cathode resistor: good shout, I was wondering how far to bend those apart. I’ve separated them more- theres probably about 3/8 of an inch between them now.
    - under board jumper tails: I’ve moved them down and to the left like you mention- not sure why I twisted them that way to begin with.
    - cc 22k dropping resistor: well these were actually the only 22k mojotone had in stock from what I remember- NOS cc resistors. Stew-Mac uses a cc 1/2w resistor there for their 5e3 kit, so I figured I’d be fine. Just in case, I just got some 2w metal oxide ones from Amazon after reading this and I’ll swap one in before I solder.
    - green insulation: I just had some extra green push back wire from the heaters, so I used that- I might strip it before I put it in.
    - caps: I’ll probably end up rotating them for easier reading, good eye. Also, I didn’t know there was a sure way to orient them north/south- I figured they don’t have polarity so it wouldn’t matter. Definitely into learning how to test them if there’s a direction that makes a difference in sound.

    Again, thanks so much for all the help. This has been a lifesaver. I’ll be sure to show updates as more stuff goes in.
     
    Last edited: May 24, 2020
  15. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,189
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    They're non-polar, but their construction makes orientation quieter one way than the other. For the how/why, I'll refer you to Mr. Aiken; but you don't need an oscilloscope if you have another amp handy. Here's how I test.

    test.png

    This is basically a ¼" plug with alligator leads to clip to a cap. The black clip comes from the sleeve of the jack (ie, ground), the red clip from the tip. Here I left some wire on the old jack to allow separation in space; it's OK without the wire.

    Then you turn the amp on, turn it down to 0, clip the other end of the gators to the cap leads, turn up (2 or so worked for me) and give the cap a squeeze between your fingers. Turn down, reverse cap, turn up, squeeze again. Start with your smallest caps where the noise is pretty obvious. It's usually clear which orientation is quieter, but if not, you can try holding the cap over the amp’s power cord. The outer foil end is the end on which the black (ground) clip is quieter. I like to mark this end with a black sharpie.

    Oh, and Aiken is a genius, but parts of that article describing where to point the outer foil end can be confusing. In a 5e3 all the (non-polar) caps on the board want the outer foil down, towards the tubes; the tone cap coming off the ground lug of the tone pot also points down to connect to your ground bus.
     
    Last edited: May 25, 2020
    hepular and JamesAM like this.
  16. muchxs

    muchxs Doctor of Teleocity

    Posts:
    13,171
    Joined:
    Aug 14, 2004
    Location:
    New England
    You'll never see 'em for obvious reasons. But... I never cross under the board jumpers over each other.

    It would be bad if I managed to squash the insulation enough to create a short.

    It would be worse if a wire shorts under the board fifty years from now. I won't be around to fix it.
     
    JamesAM likes this.
  17. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    this is great- I got here by putting a short patch cable into my amp’s input and clipping the cap leads to the jack tip and sleeve. Gave the cap a pinch and there was an obvious difference in noise depending on orientation. Thank you!!!

    @muchxs i never would have thought of your way of doing the rear jumpers, but I’m redoing them that way immediately because I have short mounting screws and can’t source any more right now. Thanks, this is brilliant
     
    King Fan likes this.
  18. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    Ok, the board is soldered and the heaters are in. I used the 18awg cloth covered wire from mojotone, and if I had to do it again- I’d use something smaller. It was tough to work with, but I got it in, twisted, soldered, and tucked under the chassis lip. Artificial CT is wired with two metal film 100 ohm resistors to a PT bolt.

    Now I’m ready to put the board in and wire the tubes and controls. For those of you who use the preamp buss:

    How do you route your pot and input jack leads from the board? Under or over the buss wire?
     
  19. King Fan

    King Fan Poster Extraordinaire

    Posts:
    5,189
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Sorry, I should wait for others to chime in -- altho I'm the guy who said you could just use a wire for a bus. I actually use solid bus bar or Romex core and float it slightly in front of or above the board on mounts, so I can't say from experience. Your wire is flush with the board, right? I'll *guess* tho that it'd be better to have the insulated leads resting lightly (if at all) on the bus wire than to have the bus wire pinching down on the leads...

    Glad to hear you're making good progress.
     
    JamesAM likes this.
  20. JamesAM

    JamesAM TDPRI Member

    Age:
    34
    Posts:
    78
    Joined:
    May 13, 2020
    Location:
    Virginia, USA
    Sorry about that- the bus is elevated now, I just kept it flush against the board (as shown in my picture) to secure it before I soldered it in. It’s now roughly about 3/16” off the board directly over the eyelets.

    I could pinch it back down flush with the board, but I wanted to see if there was a special trick you guys had for wiring the inputs and controls with the elevated bar in to ensure the leads don’t touch it.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.