Help with biasing a Rangemaster!

[FiercelyFuzzy]

Hello All

I'm currently building a Rangemaster using the PCB from GGG.
I'm using the method in RGKeens excellent GEOFex article to bias the collector (i.e. using pots to find the values of the 68K/3K9 pair) & I was wondering what value should I set the Boost pot at?
I had the collector exactly at -7.0V & then tweaked the boost pot, & of course, everything changed.  I guess boost should be set to min (0k) or Max (10K)?

Any help would be gratefully recieved!
FF

[petemoore]

I'm using the method in RGKeens excellent GEOFex article to bias the collector (i.e. using pots to find the values of the 68K/3K9 pair) & I was wondering what value should I set the Boost pot at?
I had the collector exactly at -7.0V & then tweaked the boost pot, & of course, everything changed.  I guess boost should be set to min (0k) or Max (10K)?
  10k potwafer between the transistor collector to supply is the transistors collector bias resistor, the wiper works as volume control, the pot's resistance = the fixed resistance between collector and supply.
  if the bias is changing with volume [boost?] pot adjustment, check that the potwiring has the wiper only to output cap, an outside pot lug only to collector, other outside lug to  supply.

[FiercelyFuzzy]

You are right!  I've wired the damn thing wrong.
I had the volume wiper soldered to the wrong hole on the PCB... Thanks alot!