[Boatanchors] 5U4 vs 5Y3

Brian Carling bcarling at cfl.rr.com
Sat May 24 14:48:02 EDT 2014

Seems like Fender always put more than 150 mA through a 5U4 when feeding 4 - 6L6GB tubes with about 80 to 100 watts or more of audio out. Assume 65% efficiency and 500 volts on the plate supply and do the math... It's gotta be well over 150 mA.

Best regards - Bry Carling

> On May 24, 2014, at 2:32 PM, Garey Barrell <k4oah at mindspring.com> wrote:
> Bob -
> Depends upon how much DC current is drawn.  Roughly speaking, the 5U4GB is about 150 mA of DC current supply, and the 5Y3GT is only about half that.  All sorts of limitations/variations on both depending upon cap or choke input filter, DC voltage, etc.....
> Tube data book covers all that stuff.  Bases are the same. 5Y3 draws LESS filament current, so no problem there.
> But as long as the DC current drawn is less that about 80 mA you can safely sub a 5Y3 for a 5U4, at least long enough for test.
> 73, Garey - K4OAH
> Glen Allen, VA
> Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
> and TR-4/C Service Supplement CDs
> <www.k4oah.com>
> Bob Jackson wrote:
>> Can a 5Y3 be subbed for a 5U4 for testing purposes?
>> Bob
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