Capacity of the second and following caps in Tube rectified PS ???

[kagliostro]

We know that if a Tube Rectifier is used the first capacitor capacity must respect the needs of the Tube Rectifier

so we look to the Tube Rectifier data sheet and know what to use

but what about the second capacitor in the PS chain ?

assuming to use, as an example, a GZ34, the max first capacitor must be 60uF

if we use the max usable value (60uF) than an inductor or a resistor, the following capacitors must be within a stated value or can have the values we like more to use ?

Thanks

Kagliostro

[John]

Without looking to be sure, I believe the second filter cap can be whatever you want.

For instance, on mine I used a 22 coming off the 5y3, then my second one is a 47.

[PRR]

The capacitance is not limited. The Peak Current must be limited.

You can put 10,000uFd on a 5V3 if you have 2,000 ohms resistance between (may be PT winding resistance).

You can be in trouble with 10uFd and some rediculously low series resistance at higher voltage.

The "second" cap is isolated with more impedance (resistor or choke). As long as there is enough impedance to make a 2nd cap useful, the peak current will not be large.

[chocopower]

Now you talk about this, time ago i bought and old Selmer amp with a GZ34 and a 100uf cap as first one, BUT with a 50 ohm-5w resistor between them.
Everyone said to me that the tube rectifier was in problems with that capacitance, but it worked like that for DECADES (1966), so i always suposse that the 50 ohm resistor keep the GZ34 alive.

Is my presuntion ok?

[John]

The capacitance is not limited. The Peak Current must be limited.

You can put 10,000uFd on a 5V3 if you have 2,000 ohms resistance between (may be PT winding resistance).

You can be in trouble with 10uFd and some rediculously low series resistance at higher voltage.

The "second" cap is isolated with more impedance (resistor or choke). As long as there is enough impedance to make a 2nd cap useful, the peak current will not be large.

More good info, thanks! I had only read about "the rush of current" to charge the first cap.

[HotBluePlates]

We know that if a Tube Rectifier is used the first capacitor capacity must respect the needs of the Tube Rectifier

so we look to the Tube Rectifier data sheet and know what to use

assuming to use, as an example, a GZ34, the max first capacitor must be 60uF

Funny enough, only the european GZ34 data sheet ever states a "maximum capacitor value." The american 5AR4 data sheet does not. Neither does the 5U4GB data sheet.

Notice that the Philips data sheet keeps the same maximum cap value, but shows the supply voltage raising, as long as you keep increasing the series supply resistance to limit the peak current.

[PRR]

> the european GZ34 data sheet ever states a "maximum capacitor value."

Along with a "minimum winding resistance".

They are detailing how (one reasonable way) to get the claimed output voltage and current without violating the 750mA peak current rating.

[kagliostro]

MANY THANKS for explanation & detailed infos

Kagliostro