Voltage problem with Rangemaster variant

[mordechai]

I'm having trouble getting anywhere close to the -6.5-7 volts I need on the collector of my RM project.  I checked and tested all components, the battery is fresh, and I'm using a 2N1309 PNP device with an Hfe of 100 and very low leakage.  Still, after adjusting the 5K trimmer on the emitter, the closest I can get is about -4.3 volts.  I'm attaching the schematic I'm using.  Can anybody see where the problem might be here?  Would lowering the 68K resistor to 56K help?

[willienillie]

Change the volume pot to (original value) 10K.

[mordechai]

I will do that, but why would that make a difference?

[mordechai]

Oh -- nevermind, I see why it  would matter.  Thanks for the needed slap-to-attain-awareness.

[antonis]

'Cause Collector resistor (together with Collector current) sets Collector working voltage..
(Ohm's Law..)

Collector current is already set by Emitter voltage (together with Emitter current) so, by using higher Collector resistor value, you result into higher Collector resistor voltage drop, hence lower Collector voltage..

edit: Written before "nevermind"..

[PRR]

You can instead put 16.6k across the ends of the 25k pot.

(15k or 18k is probably close enough.)

This will not get the low output impedance of the 10k pot but that may not matter in guitar cord work.