First Time Startup, a few Questions! (5E3)

Discussion in 'Shock Brother's DIY Amps' started by TobyZ28, Jan 30, 2020.

  1. TobyZ28

    TobyZ28 Tele-Meister

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    Update: It works! ;) Couldn't help myself and fired it up, played first go!!

    Need a bit of Voltage help!
    I've followed Rob's amp startup procedure with no burning/sparking/etc so far! I'm up to step 6 and noticed I have high B voltages.

    Voltages are: 440/420/312

    I'm guessing this is because of the rectifier tube that came with the kit (5AR4 instead of a 5Y3) AND/OR because the power tubes are not yet put in.

    Any experts out there able to chime in on if these voltages sound right for no power tubes/speaker hooked up with a 5AR4 rectifier? I am getting 335VAC at each of the rectifier input leads (pin 3/5 before on my setup, before the diodes)

    As for the next steps should I:
    • Still proceed with power tubes and speaker then re-measure
    • Replace the 5AR4 with a 5Y3 and repeat tests before proceeding
    • Do something else entirely
    Thanks all who've help me get this far! Here is my exact layout, B+ Voltages show are from the "Standard 5e3 voltages" image on Rob's site, not my own readings.

    5e3_Tube_Guitar_Amplifier - M V1.0.png
    PS. Using all my willpower to step on the brakes.. LOL so tempted to put the tubes in and just see what happens!
     
    Last edited: Jan 30, 2020
  2. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    Put 'em in. You know you want to.
     
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  3. TobyZ28

    TobyZ28 Tele-Meister

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    I just did... And it works !!! :D I jury rigged up the speaker cone and it sounds fantastic even without a cab (Cab is on it's way)!
    Voltages are way more in line too now, 390 | 349 | 260, all probing tests passed, power tubes are putting out nearly identical values too (+/- 0.3V) :cool::cool::cool:
     
  4. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    Amp building gets pretty addictive! Congrats on your success.

    I did 3 Deluxes of various sorts till I realised they are pretty much untameable indoors so went on to do a Princeton Reverb. Twelve inch speaker, slightly bigger transformers and the Stokes mod. It's a killer, with cleans to die for.

    Come to the blackface side!
     
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  5. The Ballzz

    The Ballzz Tele-Afflicted

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    @TobyZ28
    Congratulations on the first needle stick of your new addiction! :eek: The voltages are a tad high, so I might suggest that now is the time to try that 5Y3 and report back with what you find. Also, let us know what brand that 5Y3 is.

    Congrats Again! :D
    Gene
     
  6. The Ballzz

    The Ballzz Tele-Afflicted

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    @TobyZ28
    Congratulations on the first needle stick of your new addiction! :eek: The voltages are a tad high, so I might suggest that now is the time to try that 5Y3 and report back with what you find. Also, let us know what brand that 5Y3 is.

    Congrats Again! :D
    Gene
     
  7. Preacher

    Preacher Friend of Leo's

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    from somewhere on the interwebs

    The 5Y3 and 5AR4 (GZ34) are at opposite ends of the spectrum of the various pin-compatible rectifiers.
    The 5Y3 has the most voltage drop and the lowest current capacity.
    It's that voltage drop that creates the "sag" that amps like the 5E3 have as part of their signature sound.

    The 5AR4 (and to a lesser degree the 5V4) have a much lower voltage drop at maximum signal due to their indirectly heated cathodes.
    These tubes have a real, separate cathode; B+ does not flow through the filament when they are hooked up right.
    HINT : always pull B+ from pin 8 regardless of which rectifier you are using.
    The 5AR4 will supply a higher B+ which may exceed some component's design parameters.

    So it sounds like what the post I found was saying is exactly what you are experiencing. However that "sag" most people experience in the 5E3 is caused by the voltage drop on the 5Y3 rectifier.
     
  8. jimgchord

    jimgchord Tele-Afflicted

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    Congrats. I would echo voltages being just a tad high. See where you are with power tube dissapation then do all that again with a JJ or NOS 5y3
     
  9. TobyZ28

    TobyZ28 Tele-Meister

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    Sound's like there is consensus on the voltages being high. I'll run some more tests..

    Here are my B+ measurements vs Rob's 5E3 Typical Voltages Diagram as my Target
    Measured | Target
    B+1 390 | 370
    B+2 349 | 318
    B+3 260 | 247
    So i'm ~20V too high.

    Based on : https://300guitars.com/articles/rectifier-tube-voltage-drop-chart/
    Going from a 5AR4 to a 5Y3 would result in a 40V drop to the DC current. I would be around 20V below the target voltage. Would it make more sense to get a 5V4-GA or GZ37?
    Keep in mind I'm totally new to tubes and i have no clue how available or swappable these are - please cllue me in if I'm completely out to lunch on the above thought process :)
     
  10. Lowerleftcoast

    Lowerleftcoast Tele-Meister

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    https://robrobinette.com/Generic_Tube_Amp_Mods.htm#Rectifier_Switch

    In rob robs pages he lists several different rectifier tubes with their voltage drops. Choose on ethat will get you close. Do not buy a new rectifier tube. Only NOS or used for a rectifier tube.(or listen to others tell you different). Your choice.

    Mind the fil amp rating. Some power transformers will not tolerate 3amps on the 5v filament.
     
  11. rough eye

    rough eye TDPRI Member

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    i bought a new 5e3 when i built mine. shouldn't i have? and if not, why not?
     
  12. Lowerleftcoast

    Lowerleftcoast Tele-Meister

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    The old ones seem to last longer.
    The old 5y3 generally drop a little more voltage than new versions. A good thing usually.
     
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  13. King Fan

    King Fan Friend of Leo's

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    Not out to lunch, but overthinking it maybe? Get an NOS 5Y3. Nominal voltage drops are nominal. Let us know what you measure — and what you hear.


    Sent from my iPad using Tapatalk
     
    Last edited: Jan 31, 2020
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  14. jimgchord

    jimgchord Tele-Afflicted

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    20v isnt a big deal, but the voltage is only part of the story
     
  15. TobyZ28

    TobyZ28 Tele-Meister

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    Sounds like it, I'm still just trying to wrap my head around the rest of the story bit ;)

    I do have JJ's in for my power tubes and from the readings it sounds like they can handle my measured 370V at the plates no problem. Also I think the kit may have included the 5AR4 rectifier intentionally as they power transformer is a 330/0/330...

    I think i need to do a full measurement dump and put it up here for a more comprehensive picture.. Is there a standard format/template people on the board prefer to get? This must be something that's done very frequently on the board!

    I'll look into getting a NOS rectifier tube in parallel, i suspect the comments on my detailed measurements might help me determine what kind rectifier to go with!

    Apologies for overthinking all this, when starting out learning something new it's hard to know how to quantify "how bad" something is when it's out of spec, especially when spec is a fuzzy subjective number too! FYI I'm doing this 99% for the learning experience, not because i'm obsessing over my amps tone ;), my (lack of) playing skills do not do the amp justice!
     
    Last edited: Jan 31, 2020
  16. jimgchord

    jimgchord Tele-Afflicted

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    Yes, jjs are a 14w tube. They are pretty rugged. You still should calculate the power tube dissapation , it will help you see the whole picture better.
     
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  17. TobyZ28

    TobyZ28 Tele-Meister

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    Hi All just want to close the loop on this thread... Here are my new numbers with the JJ 5Y3-S. As everyone had mentioned, the numbers are far better and the amp still sounds great, Dissipation is at 91% with the JJ's and would be just a hair over 100 with regular 6v6GT's. B+ Voltages are just below the RobRob 5E3 Typical Voltages diagram - well within Tolerances (I think!).

    Thanks all for the advice and patience with my first-time amp questions, learn't a lot! Tube Values and Bias Measurements 2.png
     
    Last edited: Feb 5, 2020
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  18. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Congratulations on getting it up and running and sorted.
     
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  19. TobyZ28

    TobyZ28 Tele-Meister

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    Thank you for the invaluable website resource which made this actually possible for me to do!
     
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  20. robrob

    robrob Poster Extraordinaire Ad Free Member

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    You're more than welcome Toby. Z28? Are you Italian? :D Just kidding, I'm a fan.
     
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