[TCML] Home-made modulation transformer/guitar-driver (VTTC)
chriskarr4 at hotmail.com
Sat Apr 24 16:32:06 MDT 2010
So, the method of driving which you speak of, using a plate-transformer, is one in which the low-impedance signal is sent through a low-impedance winding of the plate-transformer. After going through the core, the energy is transfered to the high-voltage, high-impedance winding of the plate transformer(?). If this is the case, then fitting a new primary is a necessity.
Also, in the manner you speak of, does the circuit require two plate transformers? It seems this is the case, though I could be mistaken.
The filtering for my supply is achieved via a capacitor with the markings:
Then, it goes on to list the ratings of the three 'valid' combinations of tap-points:
"A-C 2.0MFD. 1200VDC
B-C .6MFD. 1200VDC
D-C 5.4MFD. 1200VDC"
Then, it lists a number, of which the first-half appears to be the postal-code for the company (gudeman's) mailing address:
It seems this capacitor was manufactured for Motorola, exclusively, hence the lack of information on it and its having strange values. The bottom has a red sticker which reads, "WARNING HIGH VOLTAGE APPLIED TO TRANSMITTER DURING STANDBY. TURN POWER SUPPLY SWITCH TO OFF FOR SERVICING."
The capacitor is designed to be mounted with its leads facing down-ward, mounted via four screw-points on its case. If anybody has a capacitor similar to this, or has information on it, please let me know.
Now, back on-topic. Is this capacitor capable of providing enough DC filtering for this application? Its maximum-ratings are 8.0 micro-farads at 1,200V. The oscillator I plan on using is a push-pull set of 811As or 812s.
The transformer I am to use will be rated at around 400VRMS, though it will be multiplied by a CW multiplier (made of 942C20P15K-F capacitors and 1N4004 diode-assemblies) to 1200V, nominal output. The transformer is to be oscillator-driven, not unlike a flyback transformer, though hand-wound.
Is there any reason for which this setup might now work?
> From: dr.hankenstein at earthlink.net
> To: tesla at pupman.com
> Subject: RE: [TCML] Home-made modulation transformer/guitar-driver (VTTC)
> Date: Fri, 23 Apr 2010 22:41:11 -0700
> Using a MOT for a modulation xfmr sounds like a pretty cool idea. I
> don't know anyone who's tried it before. I do know that some of the ham
> radio guys use old plate xfmrs hooked up "backwards" for their AM rigs.
> This should work on the same principle as your MOT providing you have a
> well filtered DC supply and adequate RF bypass. What they do is plug a
> 100 watt audio amplifier into the filament winding and use the plate
> winding for the series modulator. Works pretty good. Keep in mind that
> all they are trying to do is match the low impedance of the power amp to
> the higher impedance of the plate circuit.
> Good luck,
The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail.
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