LM1876 Mute by Voltage divider.

[sofaspud]

I measure the voltage at power supply. 22(+/-)VDC correctly supplied to Power-amp but Regulator 7818 is not supplying +18VDC DMM shows below <1 vdc WHY ? I could not understand.

You should separate the power supply from the amp and figure out why you aren't getting regulated output. I can't tell anything from the pic and schematic. Are you sure the switch isn't defective?

 

[pra3718]

you are requested to view lm1876.pdf in post #12 (please ignore if seen)

Yes, Today I will try this.

 

[pra3718]

At first time, Regulator 7818 is not supplying +18VDC and 2nd time (OFF/ON) shows +18VDC. Very confusing.

"Life isn't qualified by the branded clothes I wear or fluency of my english. It's measured by the number of faces who smile when they read my post."

 

[bobodioulasso]

Try a (reversed) diode across 7818/ 7918 in/out. 1N400x type

 

[pra3718]

Try a (reversed) diode across 7818/ 7918 in/out. 1N400x type

If I understood correctly, I was thinking the same. Thank you very much.

Power Supply for Preamps

 

[bobodioulasso]

I also think the problem arose when you added the 5v regulator. Is'nt it?
You do not really need that regulator. A zenner and a resistor would do it.

 

[pra3718]

This is another helpful post...# 26

What I will do is.. First I will remove 5v regulator, then try what shows 18V regulator.
If 18V regulator works correctly with several ON/OFF then 5V Zenner will be use.
If 18V regulator does not work correctly then try for (reversed) diode across 7818/ 7918 in/out

After all 5V zenner and resistor is good idea.

Thank you bobodioulasso, you have provided good information for my home-work, Please give me time for trial.