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06-25-2024, 01:34 AM
Hi Guys
These extra resistances we add to limit surge currents are also there to enforce a high-frequency filter effect, but...
In the context of surge current limiting, you are forgetting the dynamic resistance of the diode itself, plus the PT winding resistance, plus the connecting wiring itself. All of this adds up to the fact that standard 1N4007s can be used almost universally in guitar amps <100W. For essentially no mark-up, you can use the faster UF4007. Or, if you stick with the 1N-series, use 1N4004s in series as those are as fast as the UFs.
If you are contemplating going to 3A diodes, think twice. They have huge fat leads since they are meant to cool the semiconductor die. You will find more amenable easy-to-solder and easy-to-place into eyelet leads on most integrated bridges. If you use a bridge with a CTed plate winding, be certain to add a resistor to ground off the "unused" negative terminal. Of course, there should be one off the positive terminal, as standard practice. These will prevent damage to bridge.
The voltage drop of a solid-state diode in a tube plate supply is immaterial and need not complicate the calculations. Besides, varying mains voltages and loading conditions will make an attempt at precision pointless. Another significant point is that there is only about a 15% chance of turning the amp 'on' at the mains peak voltage.
Have fun
These extra resistances we add to limit surge currents are also there to enforce a high-frequency filter effect, but...
In the context of surge current limiting, you are forgetting the dynamic resistance of the diode itself, plus the PT winding resistance, plus the connecting wiring itself. All of this adds up to the fact that standard 1N4007s can be used almost universally in guitar amps <100W. For essentially no mark-up, you can use the faster UF4007. Or, if you stick with the 1N-series, use 1N4004s in series as those are as fast as the UFs.
If you are contemplating going to 3A diodes, think twice. They have huge fat leads since they are meant to cool the semiconductor die. You will find more amenable easy-to-solder and easy-to-place into eyelet leads on most integrated bridges. If you use a bridge with a CTed plate winding, be certain to add a resistor to ground off the "unused" negative terminal. Of course, there should be one off the positive terminal, as standard practice. These will prevent damage to bridge.
The voltage drop of a solid-state diode in a tube plate supply is immaterial and need not complicate the calculations. Besides, varying mains voltages and loading conditions will make an attempt at precision pointless. Another significant point is that there is only about a 15% chance of turning the amp 'on' at the mains peak voltage.
Have fun
