V76 Output Choke DIY

[CJ]

here are the plots for the air gap vs Henries on a DIY V76 plate inductor,

this is the 250 H output choke that loads the E83F tube,

a V72/V76 EFR804s choke has about 4 to 5 ma of DC on it,

this guy has about 11-12 ma DC on it,

input signal was set to give 40 VAC across the choke,

a V76 amp was used  so that we can get a good test,

current was read off the cathode resistor as was done on the V72 choke

this prevents false readings due to test lead capacitance

we snipped the output cap lead so that the AC cathode current = the choke current,

core saturation due to no gap pushes the curve down  more compared to the V72 as this choke caries twice as much DC,

looks like an 8 mil gap will get us our 250 H @ 20 Hz,

max inductance was with the 5 mil gap,

another test was run which checked inductance vs frequency for different AC voltage levels on the choke, 5-10-15-20-25-30-35 and 40 VAC,

they all plot out about the same, so no use showing a graph,

 

[Landins]

Could it be said that difference from ef804/v72 and v76 output -choke is mailnly in the airgap as the output carries more DC? Thanks for insight on these objects.

Kindly

 

[CJ]

more DC current means bigger wire, which means fewer turns, which means bigger core, which means lower DCR, which means Happy Holidays i hope,

 

[Landins]

Sounds sound. AWG 40 will handle 13 something ma. Just hope santa bring some nice cores and an LCR meter.

 

[lukas]

....someone knows, how much winding turns for choke bv515?