[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: [TCML] Re: VTTC Sound Generation
Hi DocHank,
Have you or others used fullwave rectification on say a 4 or 5KV volt plate
transformer. I seem to remember someone writing the doubler gives it a
better shot in performance. I would think a Plate transformer would be
better for audio modulation for us old timer heavy iron types :-^) I believe
John Freau has commented on this.
I have (4) RCA 833a's and original Johnson sockets, top caps, and plate and
grid heatsinks. I also have rat-holed a couple of Big mica Sagamo, white
transmitter caps and other classic micas.
When I build this one, it will use a nice piece of furniture and be a
tribute to my Dad who got me interested in electronics at 7 years old by
building a crystal radio and a board with a light, bell, knife switch and
completed circuit around the board to a battery - cool thing to do for your
kids!
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of dr.hankenstein@xxxxxxxxxxxxx
Sent: Saturday, May 31, 2008 7:47 AM
To: James Zimmerschied
Subject: [TCML] Re: VTTC Sound Generation
Jim
First of all, I am assuming you are using a MOT with or without a level
shifter on your VTTC. (That part doesn't really matter) and you are
obtaining good sparks in CW mode, but when you connect the Staccato
controller to the circuit, the sparks are "wimpy"? Maybe you have even
adjusted the "duty cycle" control to no avail? The duty cycle control also
seems to act like a "phasing control" and not only tells the tube how long
to stay on, but when to come on. The tube can only conduct during the
positive part of the wave, so if you try to turn it on at the wrong time
(such as during the negative portion of the cycle), it simply won't conduct,
or if it does, the output will be very wimpy at best. Maybe it's just a
phasing problem:Try reversing the staccato controller supply transformer's
leads. This will shift the pulse phasing 180 degrees and the run the duty
cycle control through it's paces. Also, I have noticed that some of the
staccato schematics out there do not provide en
ough duty cycle when built as shown. You may want to play around with
that. Still others have "bust mode" and other sorts of bling which I find
totally unnecessary.
Personally, I am using a 40amp / 800volt SCR. I have used a 40amp / 600volt
Triac with the same output results. However, if using an SCR, you need the
swamp the gate to kathode with a 390ohm-1/2W resistor in parallel with a
.01uf ceramic cap and the series-limit the 12V pulses from the Steve Ward
board with about a 100~150 ohm resistor to the gate. You'll have to
experiment with this value for consistent results. I did notice, if using a
triac, you can get away without any resistors or caps at all.
----- Original Message -----
From: James Zimmerschied
To: dr.hankenstein@xxxxxxxxxxxxx
Sent: 5/30/2008 9:19:16 PM
Subject: Re: VTTC Sound Generation
Woo,
Thanks for the information on the sound source. I am using Steve's circuit
but I don't get a very strong signal off the triac/scr. I may have a bad
solder connection somewhere. What SCR type are you using?
Thanks
Jim
----- Original Message -----
From: dr.hankenstein@xxxxxxxxxxxxx
To: James Zimmerschied
Sent: Monday, May 26, 2008 1:33 PM
Subject: RE: VTTC Sound Generation
Jim,
What circuit are you using that is giving you problems with the staccato
circuit? If you are using the "Steve Ward" design, you shouldn't be having
any issues as this is a pretty straight forward design. As far as grid
driving goes, I am using an oscillator/modulator/mixer in the front end and
feeding the low level signal into a mosfet 100 watt 30~500khz power
amplifier which drives the grid via a coupling transformer. Of course, the
grid must be properly biased to prevent the tube from excessive current
draw. At present I am working on a positive feedback circuit with phasing
control from the coil's secondary to the oscillator's input to improve
issues with oscillator drift. Unfortunately, work has gotten in the way of
my fun, so the project is on hold for now.
Woo
----- Original Message -----
From: James Zimmerschied
To: dr.hankenstein@xxxxxxxxxxxxx
Sent: 5/23/2008 7:01:36 PM
Subject: VTTC Sound Generation
Dr H,
do you have any circuit information for coupling a sound source to the VTTC
grid? I have a VTTC and have had trouble getting the staccato circuit to
work correctly. I am assuming the sound source intermittently grounds the
grid.
Thanks in advance.
Jim Zimmerschied
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla