03-09-2023, 04:31 PM
OK. After having thought about it, and then looking at some other RCA contemporaries (like R-7 Superette) I think I know what this choke is for and what value it should have.
If one looks at the Superette sch, it shows a choke used in the same way, but with much lower DC value. Like 80 Ohms.
Then something told me, that this tube, 55, being both 2nd detector and Pushpull driver, might be simply using an RF choke, in the same way Philco 70 or 90 use it after the plate detector, to simply filter RF from getting to the output of the tube. So the value of the similar chokes being a few mH, this is probbaly what it should be. from 1 to 5 mH. A filter together with C23.
It is certainly NOT there to compensate for frequency response on low. If anything, at low frequencies the reactance of the primary's inductance is across the load, and, being low, it diminidhes the Low output. Adding another inductance will simply divide the signal further between that shunted load and that choke.
And at high it will be in series with the parasitic (leakage) reactance and the load, and will again be used as a loss element.
What I am not sure why they used such a large coil. I at some point subbed this choke at Philco 20 with an axial small inductance, and I think I will simply do this again.
If one looks at the Superette sch, it shows a choke used in the same way, but with much lower DC value. Like 80 Ohms.
Then something told me, that this tube, 55, being both 2nd detector and Pushpull driver, might be simply using an RF choke, in the same way Philco 70 or 90 use it after the plate detector, to simply filter RF from getting to the output of the tube. So the value of the similar chokes being a few mH, this is probbaly what it should be. from 1 to 5 mH. A filter together with C23.
It is certainly NOT there to compensate for frequency response on low. If anything, at low frequencies the reactance of the primary's inductance is across the load, and, being low, it diminidhes the Low output. Adding another inductance will simply divide the signal further between that shunted load and that choke.
And at high it will be in series with the parasitic (leakage) reactance and the load, and will again be used as a loss element.
What I am not sure why they used such a large coil. I at some point subbed this choke at Philco 20 with an axial small inductance, and I think I will simply do this again.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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