Newbie Transformer Secondary Combination Qs--Plitron Example - diyAudio
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Old 11th March 2004, 07:08 PM   #1
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Question Newbie Transformer Secondary Combination Qs--Plitron Example

Greetings Fellow Tweakers,

I have some rather basic transformer questions that I could not answer with an archive search. I hope they will be of general interest.

I'm hoping to buy a versatile transformer, that I can reconfigure to create various output voltages as I experiment with various circuits and tubes. Hence the following questions.

I realize that some of the actions I ask about might cause explosions, sparks, and fire, which is why I am asking rather than doing.

Okay, for this example, please check out this Plitron transformer--my questions will relate to its various terminal numbers. . As one can see, it has two 120VAC primaries, and many secondaries.

Okay...

Okay, first, what is the implication of the dual primaries? Is there any difference between powering both, or just one primary? Could one connect 2 and 3, and apply 120VAC across 1 and four (connect the two primaries in series) to get *half* the specified voltages across the secondaries?

Second: Can I combine secondaries to add their output voltages?
For example, there is 678VAC between 6 and 7, and 342VAC between 8 and 9. Could I connect 7 to 8 to get 1020VAC between 6 and 9, and then rectify that?

Third: If my second proposal would result in sparks and death, could I rectify 6 and 7 alone, and 8 and 9 alone, and then combine their rectified output to get a higher DC voltage (I am a little more confident that this method would work, but would rather not build two separate rectifiers).

Thanks for you insights and tolerance of my cluelessness.

Best,

George Ferguson
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Old 11th March 2004, 07:45 PM   #2
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"Thanks for you insights and tolerance of my cluelessness."

This says it all.

Stay away from anything resembling high voltage.
Your friends don't want to see you dead.
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Old 11th March 2004, 08:08 PM   #3
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You have to start somewhere Frank. I consider myself a competent valve amp builder (For my personal needs). But I got a post over at Audioasylum that went like this ...

"Someone get me rope"
because I did not understand why in an unloaded psu the voltage did not drop across voltage dropping resistor.

Don't underestimate a person's ability to learn! What have you taught George here?
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Old 11th March 2004, 09:50 PM   #4
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Reminds me of my TV 405 line servicing days when I used to <get stung> by the EHT of the line o/p .......inevitable clip of the elbow on the topcap....ch**t

That Plitron tranny rated at 723W 0.65A could sting you hard if you mishandle it....It looks a hard and high way to learn......remember alot of DMM's don't like going above 600VAC.

The good regulation factor of +/-3% for that 700V winding is indictative of no-nonsense power capability....with suitable PIV full bridge rectum + suitable cap you will hit 1KV.....watch it.......

rich
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Old 11th March 2004, 10:20 PM   #5
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Bas said:
Quote:
Don't underestimate a person's ability to learn!
That's the spirit! Thanks.
Quote:
In order to become wise, one has to be willing to look clueless.
Criticizing a neophyte is too easy, so I don't waste my time either doing it or responding in kind. In grad school I was always the guy in the front row, raising my hand to ask the "stupid" question, while the rest of the class sat silent, afraid to look ignorant. Teachers loved me.

My friends, or the merely generous, will answer my questions in the spirit that I posed them. If not, I will learn the answers elsewhere, and post them here so that others may learn from my ignorance.

Quote:
That Plitron tranny rated at 723W 0.65A could sting you hard if you mishandle it
Thanks Rich and don't worry--no hardware until I know what I'm doing. For the time being, the only stings I'll be getting will be verbal.

By the way, how much voltage won't kill me?

Best,

George "Grasshopper" Ferguson
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Old 12th March 2004, 05:36 PM   #6
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Default Connecting Tranformer Primaries or Secondaries in Series

Hey All,

Well, I went ahead and found some answers on my own.

Looking at this transformer primer from Glass Audio (particularly "Modifying Transformers" and Figure 7), it seems my idea about connecting primary or secondary windings in series was correct--doing so effectively changes the windings ratio and the resulting voltage.

Since no one gave me any specific information, I'm guessing the negative and non-reactions were because I picked a high-voltage transformer to use as an example for my questions.

As always, I invite your constructive feedback. Flames will be cheerfully ignored.

Best,

George Ferguson
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Old 12th March 2004, 05:52 PM   #7
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George, yes you can series those 2 windings. Now, with that said the top winding is rated for 65mA and the second is rated for 30mA. If you put these two in series then the current rating of the second winding limits the combined series output to 30mA. You could draw more current than that if you want but don't be supprised when winding 2 burns up.

Later
BZ
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Old 12th March 2004, 06:04 PM   #8
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Bas,

I'm sorry if I sounded rough. IMHO you don't learn tube technology by screwing around with 678VAC and 1020VAC windings on transformers. You must first understand that this kind of voltage can kill you.
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Old 12th March 2004, 06:41 PM   #9
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Hi Frank,

Quote:
You must first understand that this kind of voltage can kill you.
True

The point I was trying to make is that I with very little electronics knowledge have built a decent valve amp

Along the way I have been shocked quite a few times and asked some very dumb questions. But then again even qualified/knowledgable folk get shocked.

But you are right...can't harm to keep warning people that it is dangerous playing with high voltage.

Cheers,

Bas
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Old 12th March 2004, 07:17 PM   #10
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Perhaps out H.V chap ought to change his....to H.V Batman and fly out the rest......he's done well and past the test....sofar.

Viva H.V
rich!
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