What is the correct way to get 0v from a one winding toroidal?

[Spencerleehorton]

Hi Jacob,

Could you explain a little more about latch up please?
And any fixes of this issue?

 

[gyraf]

e.g. https://groupdiy.com/index.php?topic=440.20

Jakob E.

 

[Spencerleehorton]

Ah ok so attaching some scotty diodes to outputs should sort it!!

 

[Spencerleehorton]

Was going to rebuild this today as I had some new 7915 which arrived but opened them up and they have sent me wrong regulators!!!

Would this circuit still be alright using 7815 and LM337?

 

[Monte McGuire]

The LM337 is an adjustable regulator, so you have to add some feedback resistors to set the output voltage - it's not pre-set to any voltage like the 7915. Check the datasheet for the reference voltage and example calculations.

 

[Spencerleehorton]

Yeah I’m using 240R resistor with 10k trim down to gnd, I was just making sure that on positive and negative rails it’s ok to use either or?

 

[Spencerleehorton]

Well I can’t get the negative supply working at all!!?? +15v is fine with the 7815, using the LM337 with 120R 5k trim and diodes across input to output only getting -1.7v from bridge diodes and -0.8v on out of 337?

This is mind boggling that I have so many problems with power!!!!

My other Psu for the Neve works perfectly when it’s not connected, when I connect up the 48v doesn’t supply to pins 2 and 3? And the 24v jumps around!!! Think I might have to change the 3055?

 

[Spencerleehorton]

Still not out of the woods but I have 14.98v and -18.30v from 7815 and 7915!

 

[gyraf]

(and you are aware that 78xx and 79xx pinouts are different?)

 

[Spencerleehorton]

Yes, I had double checked this as made quite a few mistakes before!!!

Bit strange I get a solid -18.33v out of a 7915?

I’ve got 1000uf then another 1000uf then the regulator then finishing with a 100nf?

 

[Harpo]

No load connected? A (temporary) FI 1k5 resistor will draw 10mA for a more predictable result.