ferlop

modified 10 years ago

Vacuum tube power supply

117

01:30:51

300VAC Suppy we could use this supply or similar with safety fuse. 240 RMS gives you about 316 VDC, with a load of 300 ohm it comes down to about 300 VDC.

published 10 years ago

thebugger

10 years ago

What if i accidentally reverse the mains polarity (phase and ground). Try grounding the the other end of the source and you'll notice the whole circuit becomes at mains potential. Even worse at the + of the capacitor, the AC shifts to DC with twice as high voltage, meaning it'll become 740VDC.

ferlop

10 years ago

You have to polarize the plug, in the old days, there were what the called hot chassis, TVs had hot chassis and so did the radios, I remember getting shocked when touching the back of the radio.

ferlop

10 years ago

Are you telling me that your house wiring doesn't have polarized receptacles?

hurz

10 years ago

There is no need for a polarization. You can have ground at any point in circuit. It does not change the circuit and its voltages. Its only the interpretation which will change!!!! Dont look at voltages on a single wire, which is relative to ground. Place a voltmeter to measure the relative voltage across the cap! The only thing which is dangerous is, the phase can be at chassis potential, depends on how the plug is inserted. And output to other devices must be galvanic separated by e.g. a transformer for audio.

thebugger

10 years ago

Just try and reverse the ground in this circuit and view the blue line on the scope. It shifts to one end of the scope making it a 700VDC. I think that's pretty dangerous.

hurz

10 years ago

You still reference to ground and don't look at the delta! As i said, use an EC voltmeter and read my last post again ;p

faceblast

10 years ago

if you shrink the capacitor suddenly the voltage goes super high

hurz

10 years ago

Q=C×U ; Q is constant C shrinks, so U must go up! One of the nice things in EC I love ;p

ferlop

10 years ago

thebugger,what hurz is saying that as long as you don't touch the chassis and the hot connections in the circuitry youll be fine and not elektrokill yourself........................................................................................ Dealing with electricity requires knowing how to deal with it, if you don't feel confident and sure, please stay away from all electrical equipment, it might jump and bite you

ferlop

10 years ago

hurz is helping, he has experience with the subject at hand, lets pay attention.

hurz

10 years ago

Right, if you feel uncomfortable or you have unanswered question, then do not do such dangerous circuits. Anyway, a stepup converter at 300V and more than 20mA is also very very dangerous!!!

thebugger

10 years ago

Yes indeed but with only 20mA current capacity, the voltage will quickly kneel if you touch it. Nonetheless I've set my mind on this, I've worked with everything except tubes and i think it's about time i made something with them too. So please any help will be appreciated. For the mains rectification, so it's no trouble reversing the polarities as long as i don't touch the ,,hot parts,, right?

thebugger

10 years ago

Everything should be rated 350V right?

thebugger

10 years ago

I have another problem though. The tubes i dug out are from the 50's and as you can imagine the labeling has been completely erased, so i have no idea with what I'm working with. Can't i just use an arbitrary tube?

ferlop

10 years ago

Not all the tubes are unreadable, are they?.............. If so the you don't know what you have.

thebugger

10 years ago

Almost all but some i managed to decipher. I have a dual triode of some kind and... Wait better yet here's a circuit of the tv set i got them from http://www.kn34pc.com/sch/sch_tv/tv_pirin/sch_tv_pirin.gif

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