snubberized power supply help needed

[rookiesparks]

hi ive built carlos fm regulated snubberized power supply , ime using 500va 2 x 25v secondarys,using 120r upper arm resistor and 2.7k lower arm resistors wich should give me 29v at the out put !the problem is when i measure the output it is 57 -58volts between the + and - ! ive separated the 2 sides of the power supply and both sides measure the desired 29v ! can some one point me to the problem thanks in simple terms ta see pics

 

[scottjoplin]

29 + 29 = 58

 

[neila]

Hi rookiesparks,


I really no expert here, but I think everything is just as should be expected. The schematic shows -30V and +30V on the output rails, you are reporting 57-58V between the positive and negative rails. This seems close enough to me (given tolerances between main supply voltage). What were you expecting and what are you going to use this for? Many chip-amps expect a positive and negative rail much like you are getting.


Neil A

 

[rookiesparks]

excuse my lack of knowledge, but ime building lm3886 amplifier i was under the impression that the ideal voltage is 28v ,maybe ime missing something but if i wired 58v to the lm3886 surely that is too much voltage ???? thanks

 

[scottjoplin]

It's plus and minus either side of 0V, all three connections are used. What you have measured is the potential difference (voltage) between the positive and negative supply rails. BTW what regulators have you used?

 

[rookiesparks]

lm338t regulators !

 

[rookiesparks]

help needed

hi if this power supply is suitable for a lm3886 amplifier, see attach )can some one fill in this wiring diagram , i would be most appreciated

 

[scottjoplin]

Can you post circuit of the amplifier you intend to use? Some implementations use a single rail, some a dual rail, your power supply is dual rail

 

[Mark Whitney]

A quick answer:
The plus connects to pins 1 and 5. The negative connects to pin 4.
0V/ground connects to all the grounds in the circuit.