[]|[ GorE]

Ok,my cmoy PSU uses a UA741 opamp for the ground channel with 22 K Resistor s before it and 10 K at the output of the opamp.
Powering from 1 9V cell,i get perfect +/- 4.23 V at the opamp socket.But when i insert in ANY dual opamp(tried 4),the PSU collapses to +7V and -1 V .
I have checked the amp stage for short circuits,cleaned using isopropyl alcohol but to no avail.
Gain : 6
The PSU levels remain the same regardless of whether the phones are plugged in.

 

[FallenAngel]

I know I made this mistake, but are sure you're plugging in the opamp the right way? I've flipped mine dozens of times and tried to figure out what was wrong.

 

[Pars]

Quote:

Originally Posted by ]|[ GorE Ok,my cmoy PSU uses a UA741 opamp for the ground channel with 22 K Resistor s before it and 10 K at the output of the opamp. Powering from 1 9V cell,i get perfect +/- 4.23 V at the opamp socket.But when i insert in ANY dual opamp(tried 4),the PSU collapses to +7V and -1 V . I have checked the amp stage for short circuits,cleaned using isopropyl alcohol but to no avail. Gain : 6 The PSU levels remain the same regardless of whether the phones are plugged in.

That's not exactly a stock CMoy. We'd need a schematic and probably pictures to help you at all. I assume that you implemented the ground channel to improve upon the CMoy's resistor divider virtual ground? Are you using a resistor divider to provide the VG reference for the ground channel opamp? Something such as Tangent has shown in his virtual ground article?

 

[]|[ GorE]

I have implemented the "VFB Opamp Based Virtual Ground Driver " mentioned in Tangents Vground article .
i have used 22K and 10 K(recommended by Tangent in another thread) instead of 220K and 1 K in the diagram.
And I am using 2 470uF caps after the opamp.

 

[ATAT]

whats "gain 6" i hope thats your driver circuit since your power supply shouldnt have any gain.

My reccomendation is to short the input and output of the opamps and measure the voltage split. if the split is nearly centered, then its your opamp, if its not centered at all, then its your load.

Cheers. without pictures, this thread is fairly pointless, I can go on giving potential mistakes all day without getting to the problem. Use macro mode post some pics.

 

[]|[ GorE]

Heres a pic :

22 K and 10 K used instead of 220K and 1 K.
Gain 6 is of the driver stage,NOT the power supply.
2 470 uF caps connected AFTER the UA751 between V+ and ground / Ground and V-.

PLEASE HELP ! I spend 7 hours yesterday hunched over a table getting this to work !

 

[DaKi][er]

Remove the 10k resistor
And do you mean 741, not 751? I can't find any info on a 751

 

[ATAT]

The 10k resistor shouldnt matter, but remove it just in case.

Gore did you short input and output and see the resulting voltage?
Take a picture of your circuit, I've seen tangent's schematic but that wont help us since we cant diagnose any build issues with a schematic.

 

[Andrea]

In that virtual ground circuit, I would put an OPA551 (and remove the 10K resistor).

 

[]|[ GorE]

Thanks everyone but i solved the trouble.There was too much capacitance on the battery rails.I also had a 470uF cap between the batteries terminals which was causing all hell.Removed it and voila !

The wonders of electronics ! Every simple project is a great learning experience ! Not to mention the workout my fingers get due to the dextrous component assembly !

Thanks once more.