5Y3 in an amp designed for a 5V4...it’ll fit, but is it wise?

Discussion in 'Amp Tech Center' started by cmm71, Apr 28, 2019.

  1. cmm71

    cmm71 Tele-Meister Gold Supporter

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    Hey All, I picked up a really nice 5E3 amp today. The builder designed it to use a 5V4 rectifier rather than the standard 5Y3. The previous owner installed a Weber Copper Cap WY3 which is designed to replace a 5Y3. Will this substitution have damaged the amp? I’ve got an NOS 5V4 on the way, I’m concerned that the Copper Cap (5Y3) currently installed may have stressed the circuit. Plenty of people seem content replacing a 5Y3 with a 5V4 but I’m not sure it works the same replacing a 5V4 with a 5Y3. Any thoughts?
     
  2. Dacious

    Dacious Poster Extraordinaire

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    A 5E3 will drop B+ voltage (total power) but it shouldn't.have any overall negative impact. If it's been running that way it's probably fine. Dropping voltages in the preamp might make the amp sound browner.

    Cathode biased amps tend to be fairly self-limiting and adjusting and 20-30 volts either side of 350 doesn't really affect them.
     
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  3. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Running a 5Y3 actually puts less voltage and therefore stress on the amp. You should be fine.
     
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  4. Wally

    Wally Telefied Ad Free Member

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    If one were curious, one would measure voltages and bias numbers to fully understand how the amp functions....what is the B+, which affects every aspect of the circuit. Since you have a 5V4 on the way and you have that 5Y3 emulator, it would be simple to gather that information....and to make your choice as to what you prefer.
     
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  5. mherrcat

    mherrcat Tele-Holic

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  6. Wally

    Wally Telefied Ad Free Member

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    The 5Y3 and the 5V4 both draw 2 amps on the heater filament, so they are interchangeable with the only concern being the resulting voltages.
    Tying back into this thread since the OP here has an amp that was outfitted with a solid state emulator of a 5Y3, I will add that when using emulators like that anything goes since their is no heater filament involved. One could run an emulator of the 5U4, which pulls almost twice the current of a 5Y3, a 5v4, or a GZ34/5AR4. Why would one od so? Maybe someone has a certain voltage point in mind, right?
     
  7. jimytheassassin

    jimytheassassin TDPRI Member

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    I would double check the first filter capacitor size. 5y3 typically has about a 20uf max although I've seen it said that a 5y3gt can withstand up to 30uf (no idea if that's actually reasonable). If so, ya I agree that a 5y3 should be fine

    FWIW it seems that the 5v4g can handle more filter capacitance in the first stage, than the 5y3. It's a good reason to double check
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    Last edited: May 5, 2019
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  8. Wally

    Wally Telefied Ad Free Member

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    +1 with jimmy on the filter capacitance. The 5Y3 and the 5V4 have the same basic rating there according to what I found at Duncan Tube Data.
     
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  9. jimytheassassin

    jimytheassassin TDPRI Member

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    Ya that's the part that confuses me. I always assumed 20uf was the limit based on years of accumulated knowledge. Plus a good 20uf cap is likely going to measure higher than that even still. The data sheets do show 10uf on both the 5y3 and 5v4. Yet, in my recent research on multiple audio and electronics forums, the accepted limit (on the interwebs) varies a lot more with what both will actually tolerate before suffering adversely. I was surprised to see the 5v4 touted as working well with up to 60uf. Dont quote me but it gave me pause when the OP stated the amp was designed for a 5v4. It makes me wonder what info the builder had on hand.

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  10. Nickfl

    Nickfl Tele-Afflicted

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    Those values on the datasheets aren't usually strict limits, they are suggested values. Thats why you sometimes see 10uf and other times see 20uf in the 5y3 datasheets and why people regularly use 30 or 40uf without a problem. As I understand it, the rectifier tube is damaged by excessive current draw rather than cap size itself. A larger reservoir cap will lead to more current draw during charging and especially at startup in a given circuit, but the overall circuit design will determine how big a cap can be used without damaging the rectifier tube.
     
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  11. mherrcat

    mherrcat Tele-Holic

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    So my 5E3 with a 335-0-335 PT and 5Y3GT rectifier has filter cap values of 22/16/16.

    Will changing the filter cap values to 30/22/16 make much difference with either a 5Y3 or 5V4 rectifier?
     
  12. Wally

    Wally Telefied Ad Free Member

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    What difference are you seeking?
     
  13. mherrcat

    mherrcat Tele-Holic

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    This is actually a two-part issue and started in another thread with someone saying they thought my voltages were low and referenced a Weber 5E3 layout from Rob Robinette's site.

    Part 1

    My PT is 335-0-335 and voltages read:

    5Y3GT
    B+1 = 337 VDC
    B+2 = 298 VDC
    B+3 = 219 VDC
    Plates = 327/324 VDC

    With a 5V4 I get:

    B+1 = 364 VDC
    B+2 = 323 VDC
    B+3 = 236 VDC
    Plates = 353/350 VDC

    Part 2

    The amp seems to be a little "flabby" and low-end heavy so I was reading that higher voltages and/or a higher first stage filter capacitor might "tighten it up" so I thought I might give it a try, but I want to make sure I am not stressing the PT or rectifier.
     
  14. Wally

    Wally Telefied Ad Free Member

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    I remember those numbers now. There are things that were not touched on in that thread. I am not a moderator, but it seems to me that taking this capacitance question back to that thread might be advisable. In short, I would wonder about. A lot of things in addition to rectification and filter capacitance. What OT? What speaker? Heavy pick attack?
    Ime, a good 5E3 can yield very lively, very clean sonics with the volume on up the dial. I never run one below halfway...and prefer it to be around 2-3 o clock.....6-8 on the dial. Heavy pick attack precludes these results. I save the heavier pick attack for those Neil Young corral distortion moments. I never beat on a guitar.
    I like a stock 5E3. I like them with true vintage P12Q’s speakers or something of that ilk.
    There are lots of ways to change things, though.
     
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  15. BobbyZ

    BobbyZ Doctor of Teleocity

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    The Weber Copper cap differs from a tube in a few ways. As Wally pointed out, no heaters so no worries about heater current. That's really nice if you want a tube rectifier vibe but have a PT with no 5 volt winding. Or like Wally said you want a 5u4 type thing in a 2 amp, amp.
    Since these are solid state, the filter cap limitations of a tube rectifier shouldn't be an issue.
    If I remember right the Weber CC also handle a heck of a lot more current than the tube they replace. Opens up some possibilities for a 5y3 type voltage drop in amps that'd eat a real 5y3.
     
  16. Wyatt

    Wyatt Tele-Afflicted

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    This is what I get for not reading the last post, @BobbyZ beat me to it.

    The OP has a Weber Copper Cap WY3 installed, not a real glass 5Y3, so the reservoir cap capacitance shouldn't be an issue at all. The Copper cap is a solid-sate rectifier with an inrush-limiter and a sag resistor picked to match the voltage drop of a 5Y3.

    BTW, Fender Champs paired with 5Y3GT and 40uF reservoir caps starting sometime in the BF era.
     
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  17. Wally

    Wally Telefied Ad Free Member

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    Wyatt, regarding the use of those 40mfd caps in the Champ and Vibrochamps; does the fact that those circuits use a single 6V6 place less stress on the rectifier when trying to recharge the caps to keep up with demand?
    I know that the spec sheets allow that there are situations in which the limits can safely be exceeded, but I am not sure what those situations entail.
     
  18. Wyatt

    Wyatt Tele-Afflicted

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    I think everything on a spec sheet is contextual. I expect the data sheets were created to certify that the tubes met minimum industry and military standards and set a warranty and UL threshold. I use data sheets, I respect and adhere to them, but there are plenty of examples showing tubes running well beyond those specs. We've seen Fender and others push the specs on tubes for 70 years, but they had the first hand experience, warranty history, and proper valve theory training to create and test hypotheses.

    Heck, according to the spec sheet a 5V4 maximum input capacitance is 10uF! And who truly believes a 5R4 has to be limited to 4 uf!
     
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  19. jimytheassassin

    jimytheassassin TDPRI Member

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    I truly appreciate the informative discussion here on rectifier filter capacitance. I’m sorry if it derailed us a bit too far off topic. The explanation makes a lot of sense about current draw to fill the reservoir. I suppose there would have to be a real world measurement to determine if the value has been pushed too far and current near or above maximum? So I guess that’s the next point of curiosity (when it turns from good to bad and in what typical designs it’s either A-uf or B-uf). At the end of the day all we want is to avoid a blowout or excessive wear and tear on the rectifier. It certainly seems difficult to weed out the theory and fact from the speculation around the web. Cool beans


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