Rangemaster Bias Question

[phintze]

I just built a Rangemaster with a CV7003 transistor (on a Tonepad PCB) and everything works fine. My question is about biasing the transistor. Currently, I'm getting about 7.5v, but I've read that it should be somewhere between 6.8v - 7.1v. Since it's fairly close, should I worry about fixing the bias? Does that extra 0.4 - 0.7v make a big difference?

[petemoore]

  Bias by ear.

[phintze]

Well, the problem is that there isn't a bias pot in the circuit. I would have to add one, and I'm not sure if it would be worth the trouble. I guess I should do it anyway just to see for myself...

[petemoore]

  It uses a PNP transistor, but the circuit has a negative ground. Here's the schem/layout:
http://www.tonepad.com/getFile.asp?id=83
  These words bring 'it' under a light that shines where the problem probably is.
  I type about NPN Neg Gnd. schematics.
  I type about PNP Pos Gnd schematics.
  That works every time, I tried some others...
  The others that I was able to help from PNP/Neg problems converted to...one of the schematics [including transistor and PS polarity] that I type about.
  It's pretty easy to convert the reverse polarity board to a known to work for sure schematic.
  Others I think were once helped by adding a BFC [large value capacitor say bigger than 220uf ?] across the power rails, maybe try that and see if it works for sure in the case of the circuit you have there.
  That^ isn't exactly true, sometimes I type fruitlessly and in vain, confusing me and anyone reading about stuff like PS polarity or something, based on no schematic at all.
  I'd say try fix-trix..then convert to a different, 'standard' power/polarity scheme.