Rangemaster built in negative supply

[teknoman2]

I just finished drawing a schematic using max 1044 for negative power supply.
When I etched it and started step by step to populate it I made some minor changes.
I would like to tell me if those changes are correct.
1) I remove the protection diode and replace it with an 100uF capacitor (datasheet says that it icreases the oscillator frequency).
2)I rotate the polarity of C6 and C7 so negative pin goes to ground.

After those changes I measure voltage on pin 5 -8.92v and on transistor collector -7.3V.
But my issue is that I have hum when I roll up the boost.
Do you believe that hum will disapear if I put it in a box?

[davent]

Pin 5 of the MAX1044 is -ve voltage out so no capacitors should be reversed, the schematic shows them correctly oriented.

http://www.geofex.com/circuits/voltpmp3.gif

I would leave the protection diode in, the IC and transisitor aren't cheap to replace.  i would add a 100 ohm resistor between pin 5 and the rest of the circuit, has helped kill the hum in some of my builds in the past.

I currently have a darlington rangemaster with MAX1044 power supply on the breadboard, no hum, very quiet.

dave

[teknoman2]

So you think that the cause of hum is the reverse polarity of capacitors C6 and C7?
Despite the wrong polarity capacitors why I still have -9v on pin 5 of max1044?
Why we put C6 and C7 capacitors on the max 1044, are they working like a low pass filter?

[davent]

If the caps aren't hooked up correctly they aren't going to be doing what they are there to do in the circuit.

Charge pump explanation; http://www.geofex.com/circuits/+9_to_-9.htm

[teknoman2]

I will flip them and hopefully the hum-whine will disappear.