5e3 expert opinions

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

  1. JamesAM

    JamesAM Tele-Meister

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    Hi everyone,

    This is my first post here on TDPRI, and I apologize in advance for the length.

    I bought a 5e3 clone about 10 years ago that’s always had some issues, and I’m finally getting around to sorting them out. It’s really noisy cranked, but I can’t say for sure if it’s new noise or if it’s always been that way because I’ve only rarely been able to really open it up. It sounds amazing at low volumes.

    The amp has sat idle for maybe 5 of the past 10 years with some intermittent playing. I turned it on last week for the first time in a while, and there’s some definite 120 cycle hum with a fluttering sound in the background- figured since I’ve had it for 10 years and it was built 6 years before that, that sound is AC ripple and it’s time to swap out the electrolytics. I’ve bought new TAD filter caps (20, 20, 16 to tighten up the bass) and some other parts from mojotone to sort it out. Im hoping you all could take a look at the inside to see if there’s anything else I should look at while I’m in there. I’ve worked with amps before so I’m comfortable soldering, working with high voltages, and discharging caps.

    Now for the rest of the story, which I actually joined TDPRI to tell you guys. Whoever built this amp really made some interesting engineering decisions, and I’m hoping that there’s a chance that they may be on this forum to walk me through what’s happening here. First, the good:

    - extremely nice lacquered tweed cabinet that looks like solid wood
    - what looks like a real vintage Jensen p12n that sounds incredible
    - really cool NOS Raytheon 5y3 and Marconi coke bottle 6v6g power tubes

    The puzzling (pics below):

    - instead of a 270 ohm 5w ceramic resistor coupled with a 25uf cap going into the filter caps, what looks like a 3w 120 and 3w 240 metal oxide are wired in series and jumpered to the cap. I guess that would work, but that can’t be safe, right?
    - instead of a 4.7k 2w metal film resistor connecting the first and second filter positive leads, there’s a 5k 5w ceramic resistor. No idea why.
    - the lead dress needs some work out of the power transformer, which I’m planning on fixing.
    - it looks like the eyelet board was screwed to the chassis before the electronics were soldered on, so the jumpers that would usually go behind it are in front.
    - the ground scheme is funky- instead of a center tap, there are a bunch of ground points to a brass plate at the top of the chassis where the pots are.
    - I discovered about a year ago that on the foil on the inside of the back panel, it’s etched that the amp was built in 2004 by Stu-daddy Hopkins with a lifetime warranty and a signature. I was super excited about this because of his awesome reputation and sent the amp to him to recap. It turns out that it’s a forgery! So I apparently unknowingly bought a knockoff Stu daddy amp from Craigslist sometime in 2011. Stu was not happy about that, and obviously I wasn’t either, because I had to ship a tube amp across the country twice with nothing to show for it.

    Anyway, I’m hoping the buzz/hum is either the old rectifier gone bad or the filter caps. The noise is always there, and increases when you turn up either volume and the tone as well. At 12, it’s really distracting and kind of unplayable. I don’t think it’s a grounding issue or cold joint, but I have no evidence to say it’s not. I don’t think it’s lead dress because the heaters are tucked away and I’ve poked around and tried to move things- no change.

    So I’m planning on swapping the filters, putting in new Mallory coupling caps, fixing the lead dress, and re-kajiggering the resistors to the correct values and locations. I think I’ll leave the jumpers where they are instead of moving them to the back of the board. I’ve also bought a new 5y3 and power tubes just in case. Based on the pictures, is there anything else I should be looking for once I’m inside? Does my description of the noise sound like bad filter caps?

    Thanks all, and again, sorry for the long post.

    0391CBB3-8056-4706-92DB-4162B691F752.jpeg FA18F73C-7CC9-497C-A83C-191B9772ECAF.jpeg 7899B022-AEDB-4136-9908-DEAD443CC67F.jpeg 9E42A84D-7743-4A60-9EE1-9875BF0337A9.jpeg 65DFF4BD-F0BE-4517-8687-DE92EE645BC5.jpeg 4BEE2B03-A6F9-49DE-AFCA-968F78753375.jpeg A24E1A8F-BB69-4F32-ACAB-8D5AD33205FE.jpeg BF0A60F0-1926-4FC9-81B2-9DE277C778EF.jpeg 9BB1BCE9-413F-45E2-9D4B-95553FAAD382.jpeg 65DFF4BD-F0BE-4517-8687-DE92EE645BC5.jpeg BF0A60F0-1926-4FC9-81B2-9DE277C778EF.jpeg
     
  2. schmee

    schmee Doctor of Teleocity Ad Free Member

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    - the ground scheme is funky- instead of a center tap, there are a bunch of ground points to a brass plate at the top of the chassis where the pots are.
    I can comment on this part and the hum. I found in building one that where you ground what is important.
    The preamp portion should be grounded near the input jacks.
    The power portion should be grounded near the power transformer and not on the control panel. At least that's what worked for me after combing grounds and having hum.
     
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  3. Ricky D.

    Ricky D. Doctor of Teleocity

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    I built a Mission 5e3 kit 12 years ago. It's very close to the original design, including the big brass plate behind the control panel for grounding. It is dead quiet at all volume levels, just a whisper of hiss at full crank.

    Bruce Collins at Mission said that it's important to use an NOS 5Y3 for the rectifier, the issue being the B+ voltage. New production rectifiers give you a B+ about 30 volts too high.
     
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  4. JamesAM

    JamesAM Tele-Meister

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    Awesome, thanks! It’s hard to tell with all those wires by the transformer, but it looks like the power section and transformer are grounded to the pilot lamp, but only with a single lead. The AC power cord is grounded to the usual place on the chassis. I’ve been looking for a long time, and I’ve never seen a layout like this. It’s wild
     
  5. Nickfl

    Nickfl Friend of Leo's

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    The two resistors in series for the cathode resistor is kind of janky but there is nothing inherently unsafe about it. The builder probably just didn't have a 5W in the value he needed. One of them looks a bit burned in your picture though, so I'd replace them while you are in there.

    Those marconi coke bottle 6v6s look a lot like JJs in your pictures. ;)

    Elevate your heater center tap on the power tube cathode resistor, that will help a lot with hum.

    Never heard of "Stu-daddy". I don't think I could bring myself to be excited that a dude who would call himself that built my amp... but its even weirder to try to imagine the guy who would pretend to be that guy.
     
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  6. JamesAM

    JamesAM Tele-Meister

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    Thanks. I’m hoping the NOS Raytheon one that’s in there now is ok and it’s just the filter caps. I bought a TAD one from mojotone- any idea if those are ok?
     
  7. Paul G.

    Paul G. Friend of Leo's

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    The exception to this is the JJ 5y3, which is pretty close to the forward voltage drop of the old ones.
     
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  8. JamesAM

    JamesAM Tele-Meister

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    I know, I had those backup JJs in there while I took the pics to prolong the life of the marconis. I’ll try to get some pics of them when I get home.

    As for the heater center tap, would it still buzz if they were tucked away under the lip of the chassis away from the signal leads? Because of how everything is laid out I might have to take them all out and re-solder them to get the leads in an acceptable position. Probably best to just do it anyway while I’m working on it.

    I thought the same thing- a really small group of people even know about Stu-daddy amps, so does it really make sense to pretend? Crazy.
     
  9. Preacher

    Preacher Friend of Leo's

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  10. JamesAM

    JamesAM Tele-Meister

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    Thanks, I know rob posts here sometimes so I’m hoping he might be able to suggest the best way to proceed if the grounding looks off. His site might be my favorite thing on the internet- it’s so helpful.
     
  11. muchxs

    muchxs Doctor of Teleocity

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    That's the way the filaments are run on 1950s originals. It's a "one wire" filament scheme. The other side of the filament is connected to ground.

    You end up with one wire 6.3v above ground.

    That's the way they did Champs right through the 1970s.

    It's just a sloppy build. Still, it has good bones. I'd take a 15 year old chrome chassis any day over current issue "EPA" chrome.

    They made chrome stick to plastic decades ago. Why can't we get good chrome on steel anymore?

    Stu Daddy is The Father of "Stood Up" filaments.

    1950s Fender amps never had the filament wiring in the way of everything . If you wire the filament string "stood up" like a 1960s Fender it's right in the way. Stu Daddy promoted that as the wildest panacea known to Man for hum reduction.

    Find the filament string in this picture. It's as quiet as most of the wiring is invisible. It's not necessarily quiet because the filament wiring is tucked away. It sure makes troubleshooting and repairs easier, though.


    HPIM3013 (2).JPG



    CAUTION! One leg of the filament string is grounded in the OP's amp. That will raise hell with the "usual" noise reduction schemes.​
     
    Last edited: May 13, 2020
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  12. muchxs

    muchxs Doctor of Teleocity

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    If I had to set that straight I'd spend my first half hour stripping it down to a bare chassis. Clean slate. Build it back up without mistakes, faux pas or shortcuts.
     
  13. Ricky D.

    Ricky D. Doctor of Teleocity

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    No idea, sorry.
     
  14. JamesAM

    JamesAM Tele-Meister

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    That’s what I was afraid of- I was hoping there was enough salvageable in this build to avoid a complete overhaul. Once I get the new caps and resistors in and the lead dress fixed I reckon I’ll see where I am.
     
  15. Nickfl

    Nickfl Friend of Leo's

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    Re: the heater center tap, see @muchxs's post. I didn't notice that your amp is wired old school with one side of the heater filaments grounded. In order to elevate the center tap, you would have to redo the heaters with twisted pairs of wire and you may have to add an artificial CT if your PT doesn't have a center tapped heater winding.

    If your hum problem is really 120hz, replacing the old filter caps may quiet it down, so maybe try that first and then move on to the heaters if you still have issues.

    As for the TAD 5y3, it is probably "ok" in that it won't harm your amp, but I'd be surprised if it gave you the same voltage as a vintage rectifier. Even the JJ 5y3, which many on the internet claim to produce correct 5y3 voltage, yields voltage a good bit higher than old production tubes in my experience. At this time, I can't see any point in buying new production 5y3 tubes, vintage examples are extremely plentiful, last a very long time, and can be had all day long for less than a current production tube.
     
    Last edited: May 13, 2020
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  16. dan40

    dan40 Friend of Leo's

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    I would start with a fresh set of filter caps and see what happens. Some rearranging of a few of the wires with a chopstick might improve the noise. You can also switch over the filament wiring to the newer scheme pretty easily. It would be nice to know the plate voltage in that amp. If it's in the normal range for a 5e3, you can switch back to the standard 250-270 ohm cathode resistor also.
     
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  17. JamesAM

    JamesAM Tele-Meister

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    Yeah, you’re right. I’ll report back when I get my parts from mojotone installed and see how things sound. In the meantime, I’ll get a plate voltage measurement to see if anything’s out of spec. I worry that since the second cathode resistor looks burned that something is wrong with the rectifier, or god forbid the PT. It could also just be that the 240 ohm resistor didn’t drop the voltage enough for the second one to handle, I guess. I’ll get some measurements and check it out. I’ve never actually checked the bias on this amp so it will be good to confirm it anyway.

    My plan is to replace the filter caps and fix the transformer lead dress and reassess from there, depending on what the voltage measurements look like. Hopefully everything will check out so I can replace the coupling caps next without messing with too many resistors.

    Thanks guys, I’ll report back and see how it goes.
     
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  18. jsnwhite619

    jsnwhite619 Friend of Leo's

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    I may have missed it, but what brand transformers are in it?

    I agree completely. I tuck mine down like the old Fenders. Out of sight, out of mind. Behind the board ground wires as well, for the same reason. I learned several tricks after I finally got my hands on a couple originals.

    IMG_20200511_174545131_HDR.jpg
     
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  19. muchxs

    muchxs Doctor of Teleocity

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    I'll hit a few high points for clarity.

    Your hum is likely a bad ground. It would be unusual for your big blue caps to fail this soon.

    Your amp is built like a very sloppy version of an original. Most of it "grounds" to the brass plate. Hassle with the brass plate in original amps was if there was a little corrosion behind it, removal and replacement of parts on the plate... the ground gets funky. There should be at least one good solid solder connection between the plate and the chassis. That's a hassle. It takes a really large soldering iron to get that one ground right.

    Sarah Richter had a better idea.

    Richter.png

    I've been grounding my amps like that as long as I can remember which is about fifteen minutes, lately.

    :rolleyes: :rolleyes: :rolleyes:

    It's an often imitated seldom duplicated setup. Everything on the preamp side of the board grounds to the buss bar. In your amp the buss bar picks up a solid ground from the inputs. Ditch the brass strip.


    Seen worse.

    I use a 250 ohm 10 watt resistor. Lotta guys worry about bias. I use NOS tubes or JJ 6V6s.

    I use a couple 1/4" spacers and air gap my resistor. Doesn't matter but I do it anyway. It doesn't even get warm.

    That's your screen grid resistor.

    There are a couple schools of thought on this. One school says use a 2 watt resistor. If tube fails the resistor burns, one of the most common sources of smoke in a tube amp. I use a 5 watt ceramic type. I can tell my tubes are failing 'cuz my amp sounds like poo when they do.

    Suit yourself. I learned the hard way. It's more work to fix someone's screwed up kit than it is to start from scratch. Sometimes it's a lot more work.

    You're already throwing parts at it. Let's see...

    Couple 6V6s, $30.

    Good deal on a 5Y3, $10. Hopefully it's a U.S. 5Y3.

    More big blue caps, $35.

    We technicians mine the Motherlode of reliable low buck caps.


    It would be helpful to see the other side of the chassis to see the transformer codes. That way we can offer suggestions about hum remediation.


    The difference between me 'n' Stu Daddy (and there are a few differences) is that I wire my filaments first. I wire 'em so they're out of the way. They don't hum and they don't cause problems.

    If yours was a real Stu Daddy the filaments were wired last. That's how you do a "stood up" string 'cuz it gets in the way once it's there.

    Another difference between me 'n' Stu Daddy is I would be inclined to tidy up someone else's crappy build.
     
    Last edited: May 14, 2020
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  20. muchxs

    muchxs Doctor of Teleocity

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    And, looking at your pics:

    Where do the first two power supply caps ground? Do they ground at all?

    Drain your caps. You'll be poking around your power supply. Then, check continuity. The negative end of your caps should connect to each other and to the grounded end of the cathode bias network. If you have a multimeter with an audible continuity check, set it to audible. Clip the negative lead to the chassis. You should be able to tell in less than three pokes. Chassis to the negative side of the caps should beep. Your amp will hum if it doesn't.

    Another hack leaves dirty tracks.

    You should never see soldering iron burns on insulation or parts. It sucks when there are burns on a $15 capacitor, even worse if there are burns on the insulation on the leads to your expensive transformers.
     
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