need help

[rookiesparks]

hi i have built this power supply (see pic)as a general unit to use with separate amplifiers that i build , the problem ime having and has vexed me for months!it works fine with most amplifiers apart from lm3886 amps ,and they play for about 5 mins then first one channel stops then the other , the chips do not get hot and have adequite cooling , and they are properly grounded , i allso have another power supply i have made using two separate transformers and it has no problem driving the lm3886amps... it apears that the chips have a protection device (spike) but cooling isnt the problem please if any body can shed some light it would be most appreciated (in laymans terms please as most tech talk baffles me

 

[rayma]

they play for about 5 mins then first one channel stops then the other

It appears the boards are designed for a center tapped secondary winding,
and you are connecting each board to a secondary winding without a center tap.

How much +/- voltage do you want for the amp? You may have to series the
two secondaries to get a center tap, if the resulting voltage isn't too much.

 

[rookiesparks]

hi thanks 35v max , think in series will be too much voltage for lm3886

 

[rayma]

hi thanks 35v max , think in series will be too much voltage for lm3886

Then you need different supply boards, which take a single winding
with no center tap and make one DC voltage, about 23V. See pdf below.

Same for the other winding. Then connect the two DC voltages in series
to make the +23VDC / 0V / -23VDC supply that you need.
You will have to share the one dual polarity supply between channels.

 

[rookiesparks]

ok thanks i will build that curcuit and give it a try ,,, many thanks

 

[MAAC0]

2 Secundaries no center tap ?? You have four wires. Join two of them.

 

[rookiesparks]

hi if i join 2 wires ile double the voltage ! if i join the other 2 ile have the same voltage still no center tap ta

 

[rookiesparks]

ive heard of a virtual ground !! has any body any idea if one would sort my problems out ?

 

[PRR]

"Virtual ground" is for NON-power amps.

Since you mention LM3886 and such, this is not what you want.

I've drawn-up your connections. Yes, the voltages add but you also have a center-point.

 

[rookiesparks]

thanks for your input , much appreciated !as my knowledge is limited but i realy need to keep the voltage under 30 dc volts to use the power supply as a general source for the majority of diy projects ,,,if i use your sugested circuit i would get 36v ac and then converted to dc (1.4 x ) would give me approx 50v dc !!! wich is too high for my needs or am i missing something thanks a. brown

 

[PRR]

The LM3886 will stand the +/-25V DC just fine.

If you are working with lower-voltage amplifiers, you got the wrong transformer.

 

[rookiesparks]

thanks for everybodys help on here , ive found the first circuit to try ,sent to me from another site, if anyb ody has a similar problem as me here is the circuit for refrence see attachment