21-04-2013, 10:46 PM
Ah - ha! Things are starting to make sense now, thank goodness. 
60 kHz and 1 nF: L = 7 mH. That sounds about right for the inductance, (especially considering that it has a ferrite core).
Using that value of L, and running at 300 kHz, (i.e. no 'real' capacitor), that returns a total stray capacity of about 40 pF: which again, sounds about right.
On the other hand, for C = 10 nF and L = 7 mH: f = 19 kHz: hmm. If it's 'happy' to run between 300 kHz and 60 kHz, which it is, I don't think it'll be too happy with that L/C ratio: the Q is too low; the cct. will squegg.
(All calculated figures above are approximate).
As for the EHT diodes, the QU37 is listed as a CV4061.
The U37 is almost identical, except has a higher current rating.
They are each 1.4 v. heater, 15 kV P.I.V., but the QU37 is rated at 100 µA whereas the U37 is rated at 2 mA.
You might consider using solid-state EHT rectifiers: the 1N6527 springs to mind. These are available on e-bay right now. Other 'possibles' are the BY140 and the BY176.
Whatever . . . you've made some significant progress, Alan, and for your persistence in so doing you are to be congratulated: well done!
Al. / April 21 //
60 kHz and 1 nF: L = 7 mH. That sounds about right for the inductance, (especially considering that it has a ferrite core).
Using that value of L, and running at 300 kHz, (i.e. no 'real' capacitor), that returns a total stray capacity of about 40 pF: which again, sounds about right.
On the other hand, for C = 10 nF and L = 7 mH: f = 19 kHz: hmm. If it's 'happy' to run between 300 kHz and 60 kHz, which it is, I don't think it'll be too happy with that L/C ratio: the Q is too low; the cct. will squegg.
(All calculated figures above are approximate).
As for the EHT diodes, the QU37 is listed as a CV4061.
The U37 is almost identical, except has a higher current rating.
They are each 1.4 v. heater, 15 kV P.I.V., but the QU37 is rated at 100 µA whereas the U37 is rated at 2 mA.
You might consider using solid-state EHT rectifiers: the 1N6527 springs to mind. These are available on e-bay right now. Other 'possibles' are the BY140 and the BY176.
Whatever . . . you've made some significant progress, Alan, and for your persistence in so doing you are to be congratulated: well done!
Al. / April 21 //
