max. uF rating NOS 5Y3GT

[Chris / CMW amps]

Hi all

I was wondering what the max. uF rating from the 1st e-cap may be with a NOS 5Y3GT rectifier and no choke.
Most datasheets say 20uF.

tia!

[MWJB]

My Champ is happy enough with 50uf, I know of folks that routinely fit 100uf with no reported problems.

[AlAmps]

Hi all

I was wondering what the max. uF rating from the 1st e-cap may be with a NOS 5Y3GT rectifier and no choke.
Most datasheets say 20uF.

tia!

Directly connected? Amp with standby and where?

Al

[R.G.]

Hi all

I was wondering what the max. uF rating from the 1st e-cap may be with a NOS 5Y3GT rectifier and no choke.
Most datasheets say 20uF.

tia!

OK. The vote in the datasheets is 20uF. What might we conclude from this about the rating?

Here's another thought - it's only the first filter cap after the rectifier that gets the huge current pulses. How about putting in a 10uF (which is what Sylvania's databook says, then put a 50uF or 100uF after a 100R resistor.

[petemoore]

How about putting in a 10uF (which is what Sylvania's databook says, then put a 50uF or 100uF after a 100R resistor.
Seems like a great approach, I'll try that sometime soon or on the next amp built/recapped. That particular part of my amps just got re-do-ing..and is doing fine enough.

[firestorm]

I'd like someone smarter than me to resurrect this thread and address the question of what is the REAL maximum capacitance ina capacitive input filter for common rectifier types. From what I understand, a lot of tube data sheets inadvertantly gave "typical" values and "max" values. Some sheets also include the advice that "higher values of capacitance than indicated may be used , but the effective plate-supply impedance may have to be increased to prevent exceeding the maximum rating for peak plate current." A lot of power transformers provide reasonably high effective plate supply impedances, calculated (for a full-wave rectifier) as Effective Plate Supply Impedance Per Plate = 1/2 the Resistance of the Secondary Winding + the Voltage Ratio of the Primary to 1/2 the Secondary at no load X the Resistance of the Secondary (usually written out as Rs= Rsec + N2 * Rpri). From what I can tell, this means that a lot of rectifiers are safer to use than commonly believed. Thoughts anyone?