Need Help With Bias Problem

[tubeswell]

The voltage divider in the bias supply is formed by R141 (as the 'upper leg' of the divider) and RV101 in series with R147 (together as the 'lower leg'). The knee, (where the voltage divider output is) is the wiper of RV101. The 51V zener limits the maximum bias voltage that can be achieved to about -51V. To shift the range of the bias voltage, you can either increase the value of R147 or decrease the value of R141. Either way, you need a substantial change to those resistances to notice much of a change in the range. (Personally I would also remove the zener).

[Axer57]

Hey guys...I have one more question. I have decided to replace the coupling caps. They are .022uf 630v Illinois Capacitors. I have some .022uf 600v polypropylene and foil film STK caps. Do you think they would be good replacements for the IC's ?