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Is there an inbuilt voltage doubler/tripler in Modern half-wave DC DST flyback or just a inbuilt diode? Answered

Hi, I have dc half wave modern type DST flyback from a   computer  CRT and put out around 30kv. I wonder: Is there an inbuilt voltage doubler/tripler in  these modern half-wave DC DST flyback or just a inbuilt diode?  I became every confused from very contradiction   info.   Why I ask? I want to know as well as I would want to build a multiplier for the flyback.   I know mine isn't the old AC type but the DST should be a DC  pulsed ...The  flyback I have just  looks like these typoical modern DST ones here: http://www.imagebam.com/image/b88cbf268367234 . Your help would be tremendously relieving for me. I have been struggling to  find out  for a while now...  Thanks a lot

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mpilchfamily
mpilchfamily

7 years ago

It's just a flyback transformer. There are no other components built in. But the transformer needs a driver circuit to feed it the AC voltage it needs to operate. SO look for driver schematics that give you the desired output from the desired input.

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leviterande
leviterande

Answer 7 years ago

Thanx for the reply!, yes I have many different drivers for the transformer. that is no problem. You said "There are no other components built in" I believe you are mistaken, this Dc transformer has at least a diode inside to rectify the Ac, all modern type flyback got a rectifier inside. What I am not sure though is whether the Flyback got a tripler/doubler as well as some people say that hmmm, its near impossible to find that out without tearing it up

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mattbeowulf
mattbeowulf

Answer 6 years ago

Sorry about the necromancy, but a Google search got me here, so I'll chip in for accuracy's sake:

You are correct, leviterande, that mpilchfamily is mistaken. While AC-only, component-free flyback transformers DO exist, they are not what anybody is likely to find and refer to as a "flyback transformer," these days.

As for your question, I've never heard of built-in voltage multipliers, but that doesn't mean much. :-) That IS a topography used for other types of high-voltage sources, like those found in ion-generators, AND many flyback transformers seem to contain the right sort of components (diodes, capacitors) onboard... but I am guessing that's not what those are there for. I think that the cathode-ray tubes these were meant to excite, take a threshold voltage level to turn on, and then some minimum amount of current to control. Given the losses inherent in each stage of a voltage multiplier, and the achievability of threshold voltages using flyback inductive effects alone, I'd expect there is little reason to add multipliers to an FBT from any CRT device.

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steveastrouk
steveastrouk

Answer 7 years ago

If its got a doubler, you won't have DC continuity from the output pin to the ground.

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leviterande
leviterande

Answer 7 years ago

Thanks Steve, I am a little confused from the different answers, I just measured continuity from the HV outputs coming from secondary. Zero continuity. The resistance was also above scale.

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steveastrouk
steveastrouk

Answer 7 years ago

Measure it the other way round.

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leviterande
leviterande

Answer 7 years ago

I did and still got zero continuity and seemingly infinite resistance...

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steveastrouk
steveastrouk

Answer 7 years ago

Try a real voltage source. The resistance is BOUND to be VERY high though

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leviterande
leviterande

Answer 7 years ago

Ok, I have connected my 24v PSU as shown here: https://www.instructables.com/id/How-to-find-the-primary-and-the-secondary-coils-of/
I Got a reading of only 3.6V instead of the "should be" 5V minimum but that's maybe alright?.
Anyway I recorded the waveform of this CRT DC flyback and what I got looked like damped AC oscillations ha?
http://www.imagebam.com/image/b35481269380401 (Ignore the freq and volt reading as the numbers were fluctuating a lot).
I measured by first having both my flyback´s 0V pin and the oscilloscope probe-ground grounded. The probe itself is 1ft away from the flybacks positive sphere terminal. I am finding this very strange that the wave looks like AC and nothing like pulsed DC... as if there was no diode inside, I am a beginner so I must have been missing something vital here . Thanks a lot for you time.

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leviterande
leviterande

Answer 7 years ago

Thanks a lot. Do you know this for sure if I may ask? have you torn up a flyback and looked inside it? Regards
levi