RE: Re: tank circuit of VTTC

["Herwig Roscher" <herwig.roscher-at-gmx.de> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

David Trimmell wrote to the list:

> Again, with up to 3 833C's filted DC 2+ KW in.

David,

Thank you for your comments. I copied your schematic and I've got 
some questions:

1. In my records I found the 833 A to have a plate dissipation of 
300 W at natural cooling and a maximum plate voltage of 3000 V. 
Does the 833 C offer better data?

2. Do you use forced air cooling for your MMC?

3. Plate voltage: Do you use a variac permanently and is your plate 
voltage 5 kV? Are there any arcovers *in* the tubes as the rated 
max voltage is 3 kV only?

4. Is there any rf bypass for C1?

5. Did you have a look at the generated wave form? Is it a pure 
sinus or is it distorted?

6. In the schematic your tank coil is not tapped. How did you 
manage the tuning?

> if you go and use a larger diameter pri conductor, then you may
> run into problems with size.
- The coil would become very bulky if I used e.g. 1/4" tubing.

> MMC is a single strand of Panasonic 0.015 uF caps, it does get 
warm, and I sugest using two strings for longer life. 
- A single strand! I'm surprised. I'll redesign my MMC if I know the 
final conductivity of my new tank coil.

> I generally run mine at 1.5 X Plate voltage.
- Did you face any MMC failures because of this small factor?

> I must point out that the meathod of Audio modulation I use 
(grid), I run the tubes at almost cutoff, with 40-50K Resitance in the 
grid leak, and the effective "pulsing" of the tube must cut the 
dutycycle down.
- That's interesting for my next step towards audio modulation.

> I did "burn" up a secondary once, it seems to get the hotest af 
anything (besides tubes
- Could you please recommend a "burn-proof" :-))  4" secondary? 

Regards,

Herwig