Tube rectifier B+ differences

[tubedood]

In my time searching this fine forum for ideas some time ago I came across a posting that gave a quick breakdown of the various rectifiers and how to get a ballpark B+ voltage. I remember that the SS diode rectifier calculation was to use the secondary AC leg to Center Tap and multiply by 1.4, I think the 5Y3 was multiply by 1.1.

If anyone has that little chart or info on the various tube rectifiers and the math to get us the B+ expected that would be great!

Dale

[Pedro Vecino]

This list can serve as a reference:

http://www.300guitars.com/articles/r...ge-drop-chart/

[tubedood]

Thanks Pedro, good chart I appreciate it. It assumes I already have a known B+ via SS diodes at 425DC. I was hoping to find the multipliers to get a B+ from the secondary such as to get a B+ from a secondary via SS diodes it works out to secondary * 1.4 … to use a 5Y3 its secondary * 1.1

Math definitely isn't one of my strong points

Dale

[Enzo]

Don't think of it as math then, think of it as arithmetic. And a pocket calculator comes in handy for the numbers.

[tubedood]

Point taken my friend Enzo. I am not afraid of trying to calculate I just wanted to be sure I had an understanding to calculate from. So if the AC secondary happens to be 290-0-290 or 350-0-350 I can figure out the B+ with the solid state 1.4 formula and the 5Y3 will always be 60 volts (more or less) lower than the SS?

I'm trying here

[Helmholtz]

This list can serve as a reference:

http://www.300guitars.com/articles/r...ge-drop-chart/

If - as I suspect - the voltage drops in the table relate to the respective max. currents and not all to the same load, results in the same amp will be different.

[Justin Thomas]

As Helmholtz said. The voltage drop is specified at a certain current draw, and if you're drawing less current than what the tube is speced at, your B+ will be higher. So, say, a GZ3R powering a single 6AQ5 may drop 10V, instead of the 17 that the spec sheet says. Even a 5Y3 is underspec in a Champ, so probably doesn't really drop all 50V.

All that said, it IS useful as a rough guide...

Justin

[tubedood]

Great folks thanks! I was hoping there were some basic guideline to what kind of B+ to expect with the various tube rectifiers.

Thanks as always you all are great,
Dale

[mac dillard]

If you are looking for the multiplier to use for each rectifier tube, these are close: SS---1.414, 5Y3 (old original)--1.1, 5Y3 (new production)--1.3, 5U4---1.2..GZ34---1.3, EZ81---1.3. you have to be careful with these numbers. Even the drops listed in the charts. All of these numbers are based on the loads on the transformer.

[Pedro Vecino]

If - as I suspect - the voltage drops in the table relate to the respective max. currents and not all to the same load, results in the same amp will be different.

Dependent on the final load, of course, but I do not think those voltage drops are necessarily relative to its maximum power capacity.
I recently had a Fender Tweed Deluxe (knotty alder handwired) that came equipped with diodes and the voltage drop when installing an american 5Y3 was exactly 60 volts.
In the Dual rectifier (4x6L6 and 2x5U4), the voltage drop is 40/45 volts at idle.

[eschertron]

I see R.G. is lurking. Not long before he straightens us out.

I'd think voltage droop is more a function of PT regulation than the diode characteristics. At PT rated load, figure 85% to 90% of the calculated no-load peak AC voltage, then subtract whichever rectifier drop you choose. I've read some threads where the discussion is about swapping the interchangeable types to get a B+ more to the user's liking.

[Helmholtz]

I suggest to do some tube data research, e.g.

https://drtube.com/datasheets/5ar4-amperex1958.pdf

Here you can find everything you need.

[Enzo]

What I THINK the OP was implying was there might be a formula for tubes like there is for silicon. In other words 1.414 x RMS is peak, which caps charge up to. Problem is the tubes, such a number will only be a gross approximation. If a tube drops 50v at rated current, that will be 50v at a wide range of voltages. So there won;t be a universal number. 50v off 450v will be a different ratio than 50v off 350v.

[Helmholtz]

What I THINK the OP was implying was there might be a formula for tubes like there is for silicon. In other words 1.414 x RMS is peak, which caps charge up to. Problem is the tubes, such a number will only be a gross approximation. If a tube drops 50v at rated current, that will be 50v at a wide range of voltages. So there won;t be a universal number. 50v off 450v will be a different ratio than 50v off 350v.

I know, that's why I don't support the OP's approach.

[mozz]

Use Duncans power supply designer. It will be very close. The more parameters you know the closer, such as secondary resistance, load resistance.