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Biggy Boy
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Posts posted by Biggy Boy
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Ya I get my SMT parts from Newark and Mouser, they would have them too.
I''d have to wait for a while until i need lots of parts before placing an order, they charge $15-20 for shipping.
Not sure what Digikey charges for shipping.
I am using the APO445 op-amps for the old project.
If and when I make the new project I'll use the MC34071 or TLE2141
But for now I'm playing with the old board, to make it work better.
If I'm not happy with the results,
then I'll make a new board using the correct new schematic and parts list.
But for now I'm playing with the the old version and experimenting. :)
Glen :) -
Had a look for MC34071 and TLE2141 op-amps at the supplier and on EBay but could not find them!
Did find and bought 3 OPA445 op-amps on EBay.
Glen -
The original project has many errors. Changing the opamps to MC34071 or TLE2141 opamps with a max allowed supply of 44V fixes only one problem.
The tiny poorly cooled Q2 transistor will melt!
The overloaded transformer might melt or catch on fire.
Many of the resistors get too hot.
The main filter capacitor's value is way too low.
The max allowed supply voltage for ordinary opamps including the TL081 is plus and minus 18V which is a total of 36V. The 28V transformer is 29V without a load which has a peak voltage of 39.6V and is reduced to 38.2V by the full-wave rectifier.
U2 and u3 also need a negative supply voltage which is -1.3v in the latest circuit so the opamps have a max supply of 39.5V. Their max allowed supply is 44V so they are fine.
Ordinary opamps including the TL081 need at least 4V for the negative supply so their total supply of 42.2V is much higher than their max allowed supply voltage.
I'll asume you are responding to me :)
Yes thats why I'm upgrading the rest of the components on the original board as suggested by you in the second post on page one of this thread.
New resistors, transistors, larger cap, extra power transistor .33 Ohm 2watt resistor.......
This parts list here!
http://www.electronics-lab.com/forum/index.php?action=dlattach;topic=19066.0;attach=16238;image
Glen -
The version with the OPA445 high voltage opamps is an old version.
Use the latest version that uses more common MC34071 or TLE2141 opamps.
Ok so I can use the MC34071 or the TLE2141 as drop in replacements for the original schematic and board I built? to replace an TL081? I'll go look at the datasheets for those two op-amps.
I checked my stock of op-amps, all I have is low noise ones for making stomp boxs 18 volt max :-\ -
Well I have decided to just mod the existing circuit board, using audioguru's part list, from post #2
I'll try that first, if it still isn't adaquite for 24 volts 2 amps, then I'll make a new board for Redwire's parts list.
Only part I could not locate at the supplier were the OPA445 op-amps.
So I'll see what I have in stock that is comparable.
I'm enjoying reading the posts!!!
Glen :) -
Hello everyone!
I built this power supply two days ago from the original site, and found this link today.
I have just spent about two hours reading every post in this thread.
LOL too funny!
Seriously that web page should be corrected or pulled down.
Anyway very entertaining.
@Audioguru Do you not get tired of answering the same questions over and over again in the same thread?
I don't understand why people don't just read the thread instead of asking questions that have been answered multiple times.
Glen :)
0-30V Stabilized Power Supply
in Projects Q/A
Posted
Well according to all of the posts in this thread and I have read every single one,
The answer is NO do not use the original schematic! Use the newer one posted in this forums thread.
Glen