After the initial measurement, I've found out that some of the secondary voltages are slightly higher than the specified values, especially those for Filament supplies.
The 12.6vAC @ 5A measures around 13.58~13.6vAC at no load. This is for the pre-amp and output tubes.
The 5vAC @ 4A measures 5.65vAC. (for rectifier tube).
Any comment if these voltage increments are just tolerable for the circuit?
Do you know your primary voltage when you did your measurements? Turns ratio is fixed so it varies with input voltage, I bet that the 220 volt input is somewhat higher. What I am trying to say is that there are two ways by which your secondary voltage will vary, one is by primary voltage, the other is the loaded voltage, you will find that once loaded, those voltages will dip, by how much we do not know yet. You can check that once you have wired up your heaters.
Btw, in building your amp, the heaters gets wired first, once done you can then check voltages and see if they are within range, for the 6.3 volts, anywhere between 5.9 to 6.9 is okey, so for 12.6 volts, 11.8 to 13.8 is fine. They will still go down once the amp B+ is connected and playing music.
The way I see it , there is nothing to be concerned about, not yet anyway. In any case should the voltages be higher when things are completed, you can add a small resistor in series to bring the voltages down, but I doubt that it will come to that.
I see you posted question about resistors, tube amps in the old days used carbon composition resistors of 5, 10 and even 20 percent. I see no reason to use 1% types today, but do not let me stop you. Carbon composition resistors are best used as grid stoppers, carbon films can be used almost anywhere….
tony
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Thanks Sir TonyT!
