Can a 5Y3 handle the load of a Princeton Reverb?

[LooseChange]

Can a 5Y3 handle the load of a Princeton Reverb?

Thanks!

[Fresh_Start]

http://www.mif.pg.gda.pl/homepages/frank/sheets/093/5/5Y3GT.pdf

DC output current 125 ma

Princeton Reverb (idle condition):
3 12AX7 @ 3ma each = 9ma
1 12AT7 @ 20ma (both triodes)
2 6v6 @ 40ma each (plate + screen = 80 ma

TOTAL 109ma

BUT - that's with the power tubes at idle.
http://www.mif.pg.gda.pl/homepages/frank/sheets/093/6/6V6GT.pdf

Page 2 - B+ at 285, 6V6 maximum for two tubes:
Plate current 92ma
Screen grid current 13ma

TOTAL 134ma

I'm not an expert, but this seems to be over the rating for the 5Y3GT rectifier tube.  The 5AR4/GZ34 is rated for 225ma which seems like a prudent cushion for this circuit.  Think about amps that use the 5Y3 like a Tweed Deluxe - two cathode biased 6v6s, a 12AX7 and a 12AY7 (6ma).

Tube data: http://www.mif.pg.gda.pl/homepages/frank/vs.html

HTH

Chip

[LooseChange]

Yes. totally helps.  Want to reduce the B+ a bit. Thanks!

[bluesbear]

A 5V4 should work. It would give you nearly the voltage drop without risk. Doug sells 'em.
Dave

[tubenit]

IIRC,   I think it was GroundHog Ken that recommended a 5Y3 in a Princeton Reverb to me yrs ago.  So when I owned my '76 PR, I did use a 5Y3GT with it. I thought it sounded good.

With respect, Tubenit

[PRR]

> 3 12AX7 @ 3ma each = 9ma
> 1 12AT7 @ 20ma (both triodes)

You got those numbers from the tube-seller. They are show-off numbers. Yes, a 12AT7 can suck 10mA at 250V. But that's actually unusual.

The 12AX7 stages are fed 240V and have 100K plate resistors. The absolute MOSt each stage could suck is 240V/100K or 2.4mA. And that only if the tube were dead-short. Dead-shorts are no good cuz there's no signal. OTOH zero-current is also no-good. Assume the "good" condition is somewhere in the middle: 1.2mA. (In this case, a bit less than 1mA, but no great difference.) Six sections at 1.2mA is 7mA.

12AT7 is a versatile tube, can be used many ways. The AA1164 schematic shows 8V across a common cathode resistor: 8V/2.2K= under 4mA for both sections.

I get 11mA, not 29mA. Nowhere near "large" compared to the power stage, but enough to matter in marginal cases.

> 2 6v6 @ 40ma each (plate + screen = 80 ma
>  B+ at 285, Plate current 92ma Screen grid current 13ma

Leo ran those 6V6 FAR outside the datasheet. 400V on plate and screen. Plate current will be well over 100mA, perhaps 115mA. G2 current may be 15% more, 130mA total. OTOH, at idle the fixed-bias runs much cooler.

Yes, the full-power load on the rectifier lays outside the Design Center ratings for a true original 5Y3. 5U4 seems a bit large for a couple 6V6, but this IS a hot-rodded amp.