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Old 11th November 2005, 04:54 PM   #1
opik is offline opik  Indonesia
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Unhappy help power supply LM4780

if this sound stupid.. i appologize...
I see the schematic, 200W power amp from electronic-lab.com , the ground come from two resistor, r: 2k in series for and the center use as ground. I want to use that on LM4780 with single supply using 10A at 50V (LM 4780 rating max at 84V & 12A). I don't want to build dual supply because i want stabilize and clean psu, if i use negative I have problem cos there are no negative IC reg in 3A just like LM338 in the positive reg. I mail the addres on the page, but he doesnt reply. I want you to know I'm bad in math. So i want to use the idea from there, like this:

{----|-------50V-----out(+)
{ |
{ /
{ / R1=?
{ /
{ |
{ |
50VAC{----0---CT---Ground
{ |
{ |
{ /
{ / R2=?
{ /
{ |
{----|-------50V-----out(-)

how much R1&R2 at 50V or more?

1. Is it safe? Is it safe when everything OK, I accidently I put my hands at the speaker?
2. how much for the R1&R2 value in above schematic/50V or more & how much watts for both R?
3. Assuming I allready have two psu at 5A each 30V DC and both using LM338 then.. if I plug them in series make them dual supply is it good/safe?
4. Please tell me anything else that I should know...

Thank You very much in advance for helping me.
kind regards,
opik, Indonesia
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Old 11th November 2005, 05:22 PM   #2
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You can't load supply by resistors. If you have center taped transformer, make some discrete regulator, it's easy, you can make it only with one resistor, one zener diode and one darlington transistor ( in each polarity ). It is basic circuit, which you can find in every textbooks...
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Old 11th November 2005, 05:30 PM   #3
opik is offline opik  Indonesia
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Default ok

thank u for helping, I realy appreciated.
I hope others can help me more, coz i realy want to use this. i see on fx pedal for guitar, there's a lot centered using resistor.
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Old 11th November 2005, 05:34 PM   #4
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My young friend, guitar pedal is different thing...But make it, how you can...
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Old 11th November 2005, 06:15 PM   #5
opik is offline opik  Indonesia
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Default ok

ok. i just trouble with the negative line, i want to use such IC for better reg at 10A.. is there any schematic using IC like LM337 parelel up to 10A? thats will solve my problem. thank you!
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Old 12th November 2005, 12:20 AM   #6
opik is offline opik  Indonesia
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Smile i found the answer

i dont realise LM333 is 3A negative supply, it cost as the same as the LM4780 and i need 3 of them to get 9A. thank you Upupa Epops for the help. anyone should know this too.!!
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