Hot to mathmaticly predict voltage sage for each added tube in circuit?

[ElectronTubesRule]

I know my target for two tubes is 2500V800ma for full output. I have to say I am not that concerned about being able to drive each tube to it's limit. What I am trying to figure out is how much no load voltage I need to arrive at 2500V@800ma. The reason I say this is because under no load conditions the voltage I chose for my filter caps will determine my final voltage. Voltage is X 10 value of filter caps capacitance is 1/10 that of caps. So if I use 450V caps I will end up with 4500V if I use 250V caps I get 2500V and so on.......

So if I end up having more voltage then I truly need was wondering if it was easier to add more tubes sense you cannot find computer grade caps in a vary wide range of values. I am thinking 250,350,450 are the over-whelming norms. Since I have 7x GI7BT tubes it is fairly simple for me to add more tubes to get things to work out well. Origanaly my plan was to build the amp with 2 tubes. Generally I take a dim view on using more then two of any tube. Past that I would normally prefer to go to a larger tube if I want more power. In this case though if their is a way to predict voltage sage under load I can use the number of tubes to balance out the available caps. So in spite of my not wanting to build an amp with more then two tubes if it solves my problem would be willing to go as large as a 3-4 tubes if it solves the problem.

I do not want to have to deal with 4500V's if I only need 2500V since any thing I do to lower that would generate more no productive heat. It is one thing to generate heat as a by product of work that is goal oriented it is another to generate heat just trying to limit voltage.

 

[GnG8d]

I think you might want check that again. What kind of voltage will the transformer make? After rectifying, you will start out at approximately 1.414 x the vac you are working with.

 

[Captain Kilowatt]

I know my target for two tubes is 2500V800ma for full output. I have to say I am not that concerned about being able to drive each tube to it's limit. What I am trying to figure out is how much no load voltage I need to arrive at 2500V@800ma. The reason I say this is because under no load conditions the voltage I chose for my filter caps will determine my final voltage. Voltage is X 10 value of filter caps capacitance is 1/10 that of caps. So if I use 450V caps I will end up with 4500V if I use 250V caps I get 2500V and so on.......

So if I end up having more voltage then I truly need was wondering if it was easier to add more tubes sense you cannot find computer grade caps in a vary wide range of values. I am thinking 250,350,450 are the over-whelming norms. Since I have 7x GI7BT tubes it is fairly simple for me to add more tubes to get things to work out well. Origanaly my plan was to build the amp with 2 tubes. Generally I take a dim view on using more then two of any tube. Past that I would normally prefer to go to a larger tube if I want more power. In this case though if their is a way to predict voltage sage under load I can use the number of tubes to balance out the available caps. So in spite of my not wanting to build an amp with more then two tubes if it solves my problem would be willing to go as large as a 3-4 tubes if it solves the problem.

I do not want to have to deal with 4500V's if I only need 2500V since any thing I do to lower that would generate more no productive heat. It is one thing to generate heat as a by product of work that is goal oriented it is another to generate heat just trying to limit voltage.

STEP AWAY FROM THE HIGH VOLTAGE CIRCUIT AND SIT DOWN. PICK UP A BOOK AND READ IT. MAKE SURE THE BOOK IS ABOUT ELECTRICAL PRINCIPLES REGARDING SIMPLE TRANSFORMER THEORY.


There. It had to be said. At this point I politely (?) point out that you have no idea what you are doing. Where the F*** did you get the idea that if you used 10 caps the voltage would be 10 times the individual voltage rating of each cap? The voltage rating is what the caps can withstand before trouble starts and the final voltage is determined by the transformer voltage as well as the type of rectifier you are using. If the transformer has a secondary output of 1000 VAC and you use a simple rectifier you will have 1410 volts DC regardless of how many caps are in the filter or what their ratings are. With a voltage doubler you will have 2820 volts with 1410 volts across each of the two caps in the doubler circuit. The number of caps or their ratings has NOTHING to do with the final output voltage.

 

[bob85]

take ck's warning
the amount of reservoir capacitance has an effect on voltage sag under load, the more cap the higher the loaded voltage at the expense of peak current in the windings and rectifiers, maybe thats what you meant and maybe its not, its not clear what you mean to me, its not something id be guessing at,

get a good book NEVER take anybody's word for it on forums, thats the last place id be asking about things that can kill me or go BANG in my face,

i have blown caps up in my youth, paper oil bits of plastic and foil splattered all over the room in your face ringing in your ears,
sounds funny but its about as funny as a shotgun cartridge filled with hot dogshit and tinsel when you aint expecting it.

 

[Captain Kilowatt]

........sounds funny but its about as funny as a shotgun cartridge filled with hot dogshit and tinsel when you aint expecting it.

Sooooooo.......I see you've been there and done that too.

 

[wavrider]

I also agree VERY STRONGLY with what Captain Kilowatt advised you to do.

Lethal voltages are present and unless you understand exactly what each component does, the purpose it serves and how to determine what is needed on a high voltage circuit then for god's sakes stay away from the high voltage circuits until you fully understand them.

Get a small 12vac secondary transformer and build you a bridge rectifier, then a full wave bridge and then a doubler circuit.

Use LOW VOLTAGE transformers until you completely understand how the circuit works.

Then once you feel confident about your abilities proceed with higher voltage circuits.

IF YOU FEEL UNSAFE, INSECURE, OR UNSURE of anything in the circuit or anything you are building then STOP for safety sakes.

Find an Elmer or someone who knows how the high voltage works, High voltage is lethal, you only make one mistake and it can be your last.

Heed CK's advice.

 

[ElectronTubesRule]

Actually I am quoting the manufacture of a pre-made voltage rectifier/doubler those are his number's not mine! I just found it late last night in my insomnia fueled search engine frenzy!

This person sells lots of kits which is why I asked the above because it goes against what I already understand! I would put up the link but it is on my laptop and I am on my desk top. The laptop has to be on for me to file swap with it.

I will post the text description directly from his site. This way you can see I am not making it up. I would prefer not to link directly to his site because I do not want any of my ignorance in any way linked directly to his products. That would not be fair to give him any negative light.



Direcetly Cut and pasted from site left out the model number to prevent any association of his products with me.

" HIGH VOLTAGE SUPPLY IS DESIGNED FOR AMATEUR LEGAL LIMIT AMPLIFIERS REQUIRING 2 - 4.5KV PLATE SUPPLIES. THE POWER SUPPLY IS CONSERVATIVELY RATED AT 4500 VDC @ 2 AMPS AND CONTAINS EVERYTHING NEEDED (EXCEPT TRANSFORMER) ON ONE PC BOARD. THE VOLTAGE RATING OF THE FILTER CAPACITORS DETERMINES THE MAXIMUM VOLTAGE RATING OF THE SUPPLY, 5 KV MAX WITH 500 VOLT CAPACITORS.

THE SUPPLY MAKES USE OF LOW ESR SNAP-IN ELECTROLYTIC CAPACITORS TO SAVE VALUABLE SPACE AND TO TAKE ADVANTAGE OF THE MANY SURPLUS OFFERINGS OF THIS TYPE OF CAPACITOR. THE BOARD WILL ACCEPT 30MM (1.18") OR 35MM (1.39") DIAMETER SNAP-IN CAPACITORS. TOTAL CAPACITANCE EQUALS 10% OF INDIVIDUAL VALUE AND TOTAL VOLTAGE RATING EQUALS 10X INDIVIDUAL CAPACITOR VALUE."

So did I miss understand everything in the above? This is why I asked you guys?

 

[ElectronTubesRule]

Trust me I have some decent books.....Electronics for Dummies figured they got that title right on the money for me!!!LOL I have a 2008 Copy or ARRL Hand Book..... I have some old books that where written in the 1950's and 60's with basic radio communication circuits and such in them too. Learning is slow process when one has work, take care of 3 boy's and attend medical school! I am getting ready to pick up the ARRL's book on AMP designs and such.

If their is one thing I know for sure my ability to communicate what I want to ask or say in written form with electronics is lacking and I know that! I often know what I want to ask but do not know how to ask it in a clear, brief easy to understand way. I am a fantastic public speaker not so fantastic writer!

 

[bob85]

http://home.earthlink.net/~wd7s/HV-2.pdf

 

[Captain Kilowatt]

Actually I am quoting the manufacture of a pre-made voltage rectifier/doubler those are his number's not mine! I just found it late last night in my insomnia fueled search engine frenzy!

This person sells lots of kits which is why I asked the above because it goes against what I already understand! I would put up the link but it is on my laptop and I am on my desk top. The laptop has to be on for me to file swap with it.

I will post the text description directly from his site. This way you can see I am not making it up. I would prefer not to link directly to his site because I do not want any of my ignorance in any way linked directly to his products. That would not be fair to give him any negative light.




Direcetly Cut and pasted from site left out the model number to prevent any association of his products with me.

" HIGH VOLTAGE SUPPLY IS DESIGNED FOR AMATEUR LEGAL LIMIT AMPLIFIERS REQUIRING 2 - 4.5KV PLATE SUPPLIES. THE POWER SUPPLY IS CONSERVATIVELY RATED AT 4500 VDC @ 2 AMPS AND CONTAINS EVERYTHING NEEDED (EXCEPT TRANSFORMER) ON ONE PC BOARD. THE VOLTAGE RATING OF THE FILTER CAPACITORS DETERMINES THE MAXIMUM VOLTAGE RATING OF THE SUPPLY, 5 KV MAX WITH 500 VOLT CAPACITORS.

THE SUPPLY MAKES USE OF LOW ESR SNAP-IN ELECTROLYTIC CAPACITORS TO SAVE VALUABLE SPACE AND TO TAKE ADVANTAGE OF THE MANY SURPLUS OFFERINGS OF THIS TYPE OF CAPACITOR. THE BOARD WILL ACCEPT 30MM (1.18") OR 35MM (1.39") DIAMETER SNAP-IN CAPACITORS. TOTAL CAPACITANCE EQUALS 10% OF INDIVIDUAL VALUE AND TOTAL VOLTAGE RATING EQUALS 10X INDIVIDUAL CAPACITOR VALUE."

So did I miss understand everything in the above? This is why I asked you guys?

OK, you misunderstood the specs. WHEW!! May I suggest the next time you cannot sleep don't bother to look for HV PSU info? When he says " TOTAL CAPACITANCE EQUALS 10% OF INDIVIDUAL VALUE AND TOTAL VOLTAGE RATING EQUALS 10X INDIVIDUAL CAPACITOR VALUE." what he is saying is that the total voltage RATING of the filter is equal to the total voltage RATING of the capacitors. If I stacked 10 caps rating for 500 volts each then the rating would be 5000 volts. That simply means that it can withstand up to 5000 volts before something goes bad. The actual voltage across the caps will depend entirely upon the transformer voltage. Maybe that is what you meant but it certainly is not what you said.

 

[ElectronTubesRule]

Well yes I was under the impression that the main determining factor for my final voltage was the starting voltage of my transformer and my diode string for all intensive purposes... The caps are just their for filtering the all the tops and bottoms that you have clipped of the ac source to create dc... The resistors are their for partial load at all times to smooth out the the difference between the rate of supply versus the rate of demand. Then I read this guys stuff and I thought you know maybe I am missing something here better go and ask..... I was really confused by what he had written and it did not agree with what I "thought I knew" I generally assume I am wrong in some area electronics being one and theology being another of them until someone tells me I am right. I was truly confused because it did not make any sense to me compared to what I "think I know".......I never assume I know anything when it comes to electronics or theology........I know where I am strong and where I am weak and that is why I ask questions on this site. I know I am weak in this area.

Reading a book on electronics theory does not make one smart on the subject matter if they do not properly understand the material or are not confident in what they "think they understand"!So I would rather ask a bunch of stupid questions and walk away with a better understanding.......then assume I understand something and get something really wrong. I have seen some tragic accidents working with Chemistry Major's that "Thought they knew what they where doing!" I am not going to be that guy!!!

I wish I was a better writer so I could communicate what I want to ask with more clarity.

I assure you my amp will turn out just fine and I am not going to kill myself in the process! I will take photo's as I go to document things. I am sure I will ask more dumb ass questions as I go. I would rather ask a dumb question and stay alive then assume I know what I am doing and end up killing myself. I have plenty of experience with high voltage and electricity, plenty of parts swamping and repair experience, zero circuit design experience! Never made any claim to being competent to design a circuit short of powering up a light bulb! I am building what other's have already built the only difference is I have so sub some value for tank circuits and voltages because I am not using a standard widely supported tube. The Russian Military Tube are kind of the white trash tubes of the amateur world......LOL

No worries my Soldering Station is broken and I have to order a new one.....LOL So I am safe from myself......It did not survive the divorce move........My lathe still works though even if it is at my father in laws house. So I can actually make some Teflon chimneys once I find a source of PTFE solid stock to machine them out of....LOL

For the record I have survived building and racing car with 1000+HP, racing cars and trucks in the 500-700HP range, building my own rifles for competition, sky diving, flying aerobatic aircraft,vintage aircraft and experimental aircraft, I have friends and family that routinely fly aircraft I helped to build, I have built about 20 tubed audio amps over the years for friends and family mostly 3 uncles and a cousin that play guitar one of them was a gift for Ted Nugget never met him myself but have family that are tight with him. I survived combat and suicide bomber's and a lot more crazy ass stuff......So this is an area of my life I have not done anything with in probably 20 years the last time I held a soldering iron in my hand was 20 year ago. No soldering in the Telcom Industry not at the field level all of that is done before we ever see a part or a harness, no soldering in the residential power or when I was working on high voltage power lines not in the sense that we do with discrete components!!!Never designed a thing all I had to do was read blue prints and schematics and make sure the right parts where installed in the right place and all the wires where hooked up per the engineers design and any additional notes in the note box!

Keep in mind my degree's are Aviation Technology and Materials Science, Business Administration and Marketing and now I am working on a Medical Degree and might double minor with Chemistry. Notice no electronic engineering class's in there....H.S. Electronics and an apprenticeship I did in H.S. and one year out of H.S. to decide if I wanted to go off to college for it that is it. I was very up front that I am reading Electronics for Dummies and the 2008 ARRL Hand Book. I have and always will be honest and up front with everyone on this board. I will not lie and I will ask stupid questions. I am sorry I am not a good written communicator. Hopefully as I learn more I will be better able to write my questions in such a way as to be understood clearly the first time for that I am terrible sorry!

As always thank you for the advice even if I do not like what you have to say or agree with it I value everyone's opinion truly I do.