Will this choke be too big?

[zippy1540]

thinking of adding a 200ohm 7hy stancor choke to my diy st35. mains here are about 125-130v so my b+ is high anyway, 390vdc to the power tubes. will this choke work?

[EWBrown]

That depends on the choke's maximum current rating, it should be rated at least 200 mA to play it safe. 7H will reduce any ripple to very low levels.

The formula for inductance is 2*pi*L*F ( 6.28 X 7 X 120 )

So at 120 Hz , the choke will be equivalent to about 5200 ohms , while at DC it is still 200 ohms.

The ST35 runs at around 150-160 mA B+ current, so a 200 ohm DCR choke will drop 30-32 VDC, which will get your B+ at the OPT's center taps to around 360VDC, which is a good "normal" operating voltage for the 6BQ5 /EL84s.

HTH

/ed B