5e3 expert opinions

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

  1. JamesAM

    JamesAM TDPRI Member

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    Thanks @muchxs and everyone else for all of your patience and help, this is all great. I haven't had the chassis out of the cabinet in a while, but I recall that the power transformer actually had the fender logo on it. Later tonight when I have some time, I'll take the chassis out and get a picture of the transformers for everyone - I definitely need to check them out.

    - Filter caps grounding: I've asked myself the same question, and I am assuming that the builder stuck to the original schematic and there's a buss behind the board connecting them to the cathode resistor and the third cap to ground them. I'm afraid to take the board off, because then we're in full on rebuild territory - that might be a foregone conclusion at this point, though. I'll check continuity tonight and report back, thanks for this great idea.

    - Power Tubes: you can kind of see in one of the pictures that both are grounded directly to the chassis via an uninsulated wire running from pins 1 and 2. The original diagram does not have these grounds depicted - could this be an indicator that the filters are not grounded, and the builder relied on grounding the 6V6es to accomplish that?

    - Other power supply questions: one green lead from the PT (I'm assuming this is a 6.3V heater filament lead) goes to the pilot lamp, and the other one goes to the star ground on the chassis with the AC power cord and the red/yellow lead on the far left. I don't think this is the center tap, as there is a green/yellow lead that's been cut off and taped. Is it worth rerouting the lead from the star ground to the pilot lamp with the other lead and the heater filament? The rest of the PT leads - primary, HV, and 5V B+ - are all in the right place. It looks like what I assume is the HV center tap (red and yellow) is routed to the bypass switch, then to the star ground. There is another additional orange wire that is routed directly to the same ground.

    - The buzz/hum sound is whisper quiet but audible when the volumes are low. It gets louder as either volume increases, with some whooshing and fluttering flap flap flap sounds underneath, which makes me think it's the filters or a power supply issue. The amp has sat idle for long periods as well. You're absolutely right though, I should be using common sense and eliminating any easy grounding issues first.

    Thanks again for all of your patience and help. I'll be back with transformer pictures, voltage readings, and continuity results later.
     
    Last edited: May 14, 2020
  2. JamesAM

    JamesAM TDPRI Member

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    I see now that the way I described the heater wiring is also the original method that Leo used (one heater lead from the PT to the lamp and one lead to ground), and at least some of the noise in the amp is just a natural consequence of that method. I still need to check the continuity of the filter caps and plate voltages. After that, assuming a good result, it looks like I have four options:

    - Install new filter caps and keep the old ground method, hoping the noise is reduced sufficiently

    - Install a virtual center tap with 2x 100 ohm resistors and rewire the entire heater filament chain, hoping the noise is reduced sufficiently

    - Do both

    - Scrap the whole thing and rewire from the chassis up - @muchxs , one thing you might agree with stu on. He called the amp as it is a "basket case" and recommended a complete teardown. This is unfortunately looking more and more like the best option.

    Two quick questions:
    1. If I decide to install the virtual CT: what should I do about pins 1 and 2 in the 6V6es? Certainly I won't be able to leave the direct ground to the chassis there, as it will result in a direct short from filament to ground?
    2. If I start from the ground up, is there a layout you recommend?

    Thanks
     
  3. dan40

    dan40 Tele-Afflicted

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    Most modern Fenders do not ground pins 1 and 2 anymore. Pin 1 is often used as a tie point to attach a grid stopper to pin 5 or can be used as a place to connect a screen resistor to pin 4. You can also leave it unconnected if you want. Pin 2 will of course be used for the new filament wiring scheme.

    Be sure that your PT does not have an actual green/yellow centertap wire for the filament winding. If it does there will be no need for the 100 ohm artificial CT. Use one method or the other but never both at the same time. For an extra bit of noise rejection, you can attach the centertap wire (or artificial CT) to pin 8 on one of the 6v6 sockets.
     
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  4. dan40

    dan40 Tele-Afflicted

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    Have you tried a new tube in v1 yet? One that you know is quiet in other amps? It may be that the noise is simply a result of a bad or noisy tube in v1.
     
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  5. David Barnett

    David Barnett Doctor of Teleocity

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    Where is she grounding the bus bar? The input jacks are insulated from the chassis.

    And why is she grounding the screen grid node with the preamp?
     
  6. David Barnett

    David Barnett Doctor of Teleocity

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    Green/Yellow is possibly a center tap for the heaters. If so, that gives you another option for the heater circuit...

    Speaking of which, if you go to a center-tapped or artificial center-tap for the heaters, you'll need a new lamp assembly, since the one you have now connects one side of the lamp to the chassis.
     
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  7. JamesAM

    JamesAM TDPRI Member

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    Yeah, I tried 2 different 12ay7s and 3 12ax7s in V1. No dice. Still hum.

    update: I checked the connectivity, but couldn’t find any alligator clips to check plate voltage. I didn’t really trust my hands’ steadiness against the chassis with a live amp, so I’ll wait until I can clip the common lead to ground and use one hand.

    The negative ends of all three filter caps show connectivity with the chassis. There must be a buss on the back side of the board that connects the first two to the cathode resistor or the third cap ground points on the control panel.

    I also compared it to my AC15hw, another amp with no negative feedback that might give a good reference for baseline noise, fully cranked on the top boost channel with the MV bypassed. The 5e3 definitely hums more, but the vox has way more hiss. At full volume with no instruments connected, you can hear the 5e3’s buzz clearly over the vox, but not by much. ive had ground noise from a failed input jack on this amp, and this is way quieter. I think this might just be the old 50s layout doing what it does, maybe coupled with 16 year old filter caps that have sat for a while.

    for those interested, I also took the chassis out of the cab for pictures in case anyone can provide more info about the transformers. Thanks again for all of your help, I’ll see what happens when the new parts come on Friday.

    A19CEDA3-361D-4D61-BBA6-AB9775919C88.jpeg 36F87051-D971-4C24-861F-AC072BE6D406.jpeg D420ED77-6AE1-47F4-AFC7-1C6D0FC6D127.jpeg
    7AC3872A-DD80-48EC-AA7D-6D2D8DAD8196.jpeg
    F61C6E48-76CD-4A37-A0A4-B41FAB14E88B.jpeg
     
    Last edited: May 14, 2020
  8. JamesAM

    JamesAM TDPRI Member

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    That’s my assumption too. Unfortunately whoever built it cut that lead off to about an inch long and rendered it unusable. I think I might just take muchxs’s advice and start from the chassis up with a new build that includes a virtual center tap.
     
  9. dan40

    dan40 Tele-Afflicted

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    With a quick search I was able to find a link that described that PT code as being a Deluxe Reverb model PT. If so then voltages should be pretty spot on when using a 5y3 rectifier. Here is the spec sheet for a Classictone PT designed for a Deluxe Reverb. It is the same model I used in my 5e3 build and it delivered a perfect 360-370vdc final B+ voltage. Your PT should be perfect for the 5e3 circuit.

    http://www.classictone.net/40-18016.pdf
     
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  10. David Barnett

    David Barnett Doctor of Teleocity

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    I've got a set of those WWII-era Canadian Marconi 6V6s, I can't remember who it was now but someone was dumping a bunch of those on the market a few years ago.
     
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  11. JamesAM

    JamesAM TDPRI Member

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    How do yours sound? They look cool but I can’t perceive any meaningful difference from the jjs.
     
  12. David Barnett

    David Barnett Doctor of Teleocity

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    I had them in a '63 BF Deluxe-Amp, they sounded fine. I was a bit worried that the 6V6G isn't rated for the 420V+ in a blackface amp, especially the screens, so I took them out. I should still have them somewhere...
     
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  13. dan40

    dan40 Tele-Afflicted

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    I would expect those old Marconi's to break up a bit earlier and compress a bit more than the JJ's. Your amp is biased a bit cool with 360 ohms in the cathode circuit. 5e3's sound the best to me when running hot with their normal 250-270 ohm cathode resistor. Your power tubes may exhibit a bit more character once you get the circuit closer to stock values.
     
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  14. JamesAM

    JamesAM TDPRI Member

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    Well, here’s an update.

    - put a new rectifier in, which helped slightly, but only at 0 volume
    - put in new 6v6s, which also helped slightly, but only at 0 volume. The amp is almost silent at 0 volume now, which is great, but still buzzes when volumes and tone are turned up.
    - pulled out V1 and the buzz disappears. Awesome, sounds like @muchxs was right and it’s not the filters at all- it’s a preamp ground issue (right?). I’ll leave the filters alone for now, but have new ones waiting just in case.
    - pulled out and cleaned the pots and input jacks to make sure they made contact with the brass plate. Still buzz.
    - the buzz is more apparent on the bright channel.
    - when I poke the input jacks, all but 1 (which is one I replaced not long ago) crackle against their ground tabs. I’ll replace the other 3, but I’m not 100% sure they’re wired correctly. When I replaced the old input jack (bright 1), I wired it the same as normal 1- it matches the mission layout.
    - like the power tubes, v1 and v2 are grounded directly to the chassis via a soldered ground lug on pin 9. The other ground in the preamp is from the v1 cathode resistor, which is soldered to the brass plate at the control panel.

    I’ll replace the input jacks, but what’s the best way to troubleshoot a ground loop before v1? I’ve chopsticked there and Can’t find any cold joints. Is there a specific course of action I should take next after replacing the input jacks? Where should I check continuity?

    additionally, is there a “best way” to wire the input jacks using the original fender layout that reduces noise?

    thanks everyone
     
    Last edited: May 16, 2020
  15. muchxs

    muchxs Doctor of Teleocity

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    I suspect everything "grounds" to the brass plate but the brass plate doesn't have a good ground to the chassis.

    I never use the brass plate. Mojotone doesn't sell them. I have a whole stack of Weber VST brass plates.

    Hassle with any discussion of "the best way" is we'll get several different "best ways" starting with Stu's legendary "stood up" filaments. There are dozens of arguments for and against various styles. At the end of the day that's what it is, style. Or lack of style.

    There are guys who will tell you big blue capacitors suck. I can tell you back when I used 'em we'd get one that was open every so often. Not a capacitor at all. It looked like a capacitor.

    There are guys who will tell you your orange caps suck.

    There are guys who will tell you your carbon comp resistors suck.

    I could tell you how I wire my input jacks. There are guys who will tell you my way sucks.

    At the end of the day what matters is tone and silence. You want tone when you're playing and silence when you're not.

    At a glance your input jacks look o.k.. They're not the way I do 'em but they're o.k.. As we've established the entire amp is generally untidy. It would be great if it had just one problem. Maybe it does have just one problem.
     
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  16. muchxs

    muchxs Doctor of Teleocity

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    Look at the original Fender layout drawing. Your anonymous builder grounded pins 1 and 2 exactly like the original drawing.

    https://schematicheaven.net/fenderamps/deluxe_5e3_schem.pdf
     
  17. David Barnett

    David Barnett Doctor of Teleocity

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    Lupe's way seems to work well enough:

    Original_5E3_Deluxe_Input_Jacks.jpg
     
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  18. muchxs

    muchxs Doctor of Teleocity

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    And...

    Fender changed "Lupe's way" post- tweed amps.

    You would be the guy who argues about the way I do 'em.
    There are three basic ways to do this. No mix and match!

    Screwing around with your filament wiring is an excellent opportunity to burn the filament winding out of your transformer. There are a few ways to short the filaments starting with the way they're currently wired and working towards a hybrid scheme. The fuse won't save your transformer if you short the filaments.

    Just for fun, let's count the possibilities:

    One, use the chassis for one leg of the filaments. It worked in 1957, it worked in 1960, it continued to work in every Champ through 1981 'cuz that's how they did it.

    Two, center tap the filaments. Warning! You need to re- wire one side of the filament string, get it off the ground. You will zorch your PT PDQ if you just ground the (clipped off) CT.

    Three, artificial CT. This is the 2x 100 ohm resistors Fender did, typically from the pilot light to a ground tap. Again, Warning! You need to re- wire one side of the filament string, get it off the ground. If you just add 100 ohm resistors you're going to smoke them on startup and maybe damage your PT. Again, the fuse may not blow before you damage your PT.


    There are elevated filament schemes and DC filament schemes in addition to the basics. I've never felt the need to deviate from the basics even in sicko high gain amps. My stuff don't hum.
     
  19. JamesAM

    JamesAM TDPRI Member

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    Yeah, I was hoping I’d missed something. That’s what I was afraid of. I can’t seem to find any other ground points that might be messed up, so I’m thinking this is a brass plate ground issue too. It’s definitely a bit loose on one side, so I worry that it reacted with the chassis and corroded.

    More and more I’m thinking that the amp in its existing layout is just buzzy and a total overhaul is the answer.

    I’ll see what happens when I replace the input jacks, which needed to be done anyway. Thanks for all the ideas
     
  20. muchxs

    muchxs Doctor of Teleocity

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    Save your old ones. They cost a couple bucks each and they're probably o.k..



    Here is my "Pancho and Lefty" story.

    Little known but Lupe (pronounced "Loopy") had a cousin Sloppy (pronounced "Slop Eh") While Lupe toiled away assembling amps up in Fullerton, Sloppy hung out at various dog and pony shows and bars in Tijuana. When Sloppy wasn't warming his favorite bar stool he could be found passed out by the garbage cans in his preferred alley.

    Lotta tweed amp builder wannabes have heard about Lupe (pronounced "Loopy"). For example the OP's amp is wired like a juxtaposition of Lupe and Sloppy. The grounding plate is wired like Lupe would have wired it, only Sloppy. The inputs are wired like Lupe wired them, only Sloppy. The ground string is wired like Lupe wired it, only Sloppy.

    Lotta wannabe builders hear "Lupe" (pronounced "Loopy") and decide their build should literally be Loopy. They figure if ten feet of five different colors of wire came with their kit they should use all ten feet each of five different colors of wire. Or even better, fifty feet of one color. Rather than committing to a build and neatly trimming their transformer leads they make their build Loopy by leaving all 18" of the leads un- trimmed. Come to think of it these must be the guys who never trim the excess string off when they re- string their Telecasters. They're usually playing with painful pricked fingertips from when they got into the loose ends of their "B" and "E" strings.

    :rolleyes: :rolleyes: :rolleyes:
     
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