6A PSU using L200

[Bluechip]

EDIT   .. BTW, your pic seems to be minus the little triangle thingy that makes it whizz round ...    any chance ?

I`m confused again Dave....... 

Why would the pic need to whizz round? 

If you mean the crank throw. It`s still there......... It all gets a little blurred at a dizzy 400+ rpm! 



David D

Those funny pics. with 'YouTube' in the botom RH corner, and a grey rectangle with a black triangle in the centre ...

Sort of shorter version of the Saturday Afternoon 'Tuppenny Rush' ..

No Candy Floss tho' 

Dave BC

[Bluechip]

Yes your right     I've saved a smaller picture
the first picture did not look that big when I saved 

would one mje2955   ( plastic pnp) not of been ok ? or even a 2N3055 ( metal npn )

I've not used the L 200 regulator my self  - thats why I am following your project

waiting for your next instalment

John

You could use a ( or more ) MJE2955, but not a 2N3055. Needs to be pnp, not npn.

On this PSU input volts is about 10V, lowest output Volts is 2.7-ish. This gives about 7.3 volts across each transistor x ( 3A )... ie some 22W.

With one it's 44W ... I used two MJ2955's to give them an easier time .. I got quite a few anyway. Will also put a box fan on it.

If you download the L200 .pdf and also the L200 Application Notes ( more circuits ), from ST.com it's all in there ..

Would post the .pdf of the Eagle Schematic but I don't know how to 

Don't even know how to post a image ... tried but failed .... 

Dave BC
 

[Stilldrillin]

Those funny pics. with 'YouTube' in the botom RH corner, and a grey rectangle with a black triangle in the centre ...

Sort of shorter version of the Saturday Afternoon 'Tuppenny Rush' ..

No Candy Floss tho' 

Dave BC

Oh..... Them things! 

I get bored wi em, after a few seconds of watching an engine whizzing. So, I only take filums of new stock. 


Drive a candy floss machine!  Oh yeah..... That's a great idea! 



Anyhow....... I think we should return to topic. 

Whatever it was ....... 

David D

[Bluechip]

Topic ????   Wot topic ... Choccy bar ??

Nowt to do wi me anyway     

Gone 

[John Swift]

Hi Dave BC ,
 I see you had two good reasons for using the MJE2955's
first you have them all ready and the pin out of the IC makes it easier to use a pnp transistors

you would need to use a pnp transistor with a npn power transistor like the 2N3055 to form a quasi -pnp transistor
like they used to do in audio amplifiers when there was not as many PNP power transistors

the first IC regulator I used was a uA723 , ideal for using with NPN transistors
Its a bit old ( like me ) but because the reference voltage came out of one of the pins and both op amp/ error amplifier  inputs , it was easy to turn the output down to zero

[Bluechip]

John

Never had much to do with discrete transistor audio amps. Built several valve Mullard 5-20's / 5-10's, but the only one I ever built was a ( Williamson ? ) pair from a kit bought by a character in the pub who then decided it was a bit beyond him ...  seem to remember MJ340 or similar. Worked OK for him anyway .. got some free beer. He was happy, I was happy... briefly IIRC...

I don't see why the comp. pair arrangment shouldn't work .. must admit I just modify stuff from the .pdf's.  There is a cct. using a 2N3055 as a pass transistor, don't know if you've downloaded the things .. but it's more involved than the pnp jobby I did. I just paralleled ( ?  spellcheck ) .. the two off with the usual emitter ballast resistors to even 'em up a bit. Not needed if you have a lot of transistors to choose from, and the patience to find a matched pair.. Can't be bothered, just ballast the damn things. QED.

I have used the uA 723, long time ago. At one time it was the device of choice, seem to remember them in a metal can .. might even still have some..

First used the L200 in 1978, a mate worked at a semiconductor/ electronics bits wholesaler. Managed to scrounge a 'developers sample pack of 10 ', never used any other adjustable reg. since then.  Bit inconvenient having to pay for them. Never forgiven him for resigning to go somewhere else better paid. No thought for others, some people ..

Dave BC

[John Swift]

Hi Dave ,
              I can see why you use the L200 regulator , it is nice and simple and the price is right  

variable power supplies I have built in the past could go down to 0 volts and one  had variable current limiting as well
with the L200 chip you need a  negative 3v supply to do that
a charge pump circuit could generate that from the positive supply or use a transformer with a centre tap ?

BTW the wiliamson amplifier was a valve amplifier , I should have the circuit
 have found on the 'net  the circuit of a John Linsley Hood design  that may be similar to your amplifier



           John

[Bluechip]

Hi John

Just looked up the Williamson amp. Too true, it is a valve amp.  So why did I think the one I did was one ??  Another bit of brain shot 

That J. L-H looks familiar, but the output transistors don't match my memory, vaguely remember MJ340 for some reason ??

It was only a pair of P.A.'s I built for him, 'cos he connected them to a posh ( Nordemende ?? ) walnut veneer radio-gram. Which had the pre-amps/equalisation stuff in it ...

I don't think there's much that can't be done by torturing a '555. .... 

Dave BC