bear in mind that as capacitors store voltage, chokes store current..http://hammondmfg.com/pdf/5c007.pdf
yes, dc voltage will be highers during startups when the filaments are stlll cold, dropping as load currents starts to flow....
the way i do it in my amps is to introduce resistances along the line so that i end up with the desired voltage when the amp is making music...
it is easy to lose voltage when you have more, than want voltages that you do not have......
in most cases this is no big deal...
yes, dc voltage will be highers during startups when the filaments are stlll cold, dropping as load currents starts to flow....
the way i do it in my amps is to introduce resistances along the line so that i end up with the desired voltage when the amp is making music...
it is easy to lose voltage when you have more, than want voltages that you do not have......
in most cases this is no big deal...
The bleeder resistance does not matter.eduard said:
A 900V transformer will give you 1260V DC once the rectifier warms up, and then about 800V under load via a choke input supply. Less resistive losses when under load.
Sorry, when you said "bleeder resistance" I thought you mean a resistor used merely as a bleeder i.e. a safety feature to discharge capacitors when switched off. What you are talking about is a load resistor to ensure that the necessary minimum current is always drawn. In this case the correct value should ensure that the DC voltage does not rise - provided that you can trust the resistor never to fail.
Hello,
YES, the resistor is there to take care there is always a minimum current running that will make the supply work as a true choke input.
Once the resistor is installed the dc voltage will not go down a lot when the circuit is also connected.
I will probably start with switching all the heaters ( including those of the 5R4GYB) after that switch on the high voltage transformer and hope it will go up in a few seconds untill the desired voltage.
Maybe i could install a string of zeners diodes with a total of about 50 volts more than the actual voltage to protect the caps from getting to much voltage.
Today i ordered the 30H 100mA 11,2 ohm total dcr.
Greetings, Eduard
YES, the resistor is there to take care there is always a minimum current running that will make the supply work as a true choke input.
Once the resistor is installed the dc voltage will not go down a lot when the circuit is also connected.
I will probably start with switching all the heaters ( including those of the 5R4GYB) after that switch on the high voltage transformer and hope it will go up in a few seconds untill the desired voltage.
Maybe i could install a string of zeners diodes with a total of about 50 volts more than the actual voltage to protect the caps from getting to much voltage.
Today i ordered the 30H 100mA 11,2 ohm total dcr.
Greetings, Eduard
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I would simply buy caps with a higher voltage rating for the case when the B+ might over-shoot. Yes, it costs more money, but generally speaking the higher voltage rated caps are also of better quality due to the thicker layers needed to handle the higher voltage.
design of the power supply begins with the load, total filament power, total plate power....then calculate the size of the core that will support required power with some headroom..i tend to overbuild my power traffo since M6 cores are hard to come by here and is so expensive...
since you are using traffos off the shelf, then be prepared to make the needed adjustments, i.e. introducing series resistances at the b+ line..
since you are using traffos off the shelf, then be prepared to make the needed adjustments, i.e. introducing series resistances at the b+ line..
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