Ok, so i have had one of the old Quadpros forever. I asked my tech to confirm bias and he measured 28ma while i was seeing 20. No doubt he was correct so after reading a thread i measured the resistance of the probe with no tube attached and it was 1.5ohms. Thinking it had worn out, i ordered another brand and it too measured 20ma at when used on the amp and so i measured the ohms again and got 1.5. Is this a coincidence and they both SHOULD measure 1.0 ohms? Is there something i'm missing in the amp like a shunt or something where it would give a different reading? Can i use it and just multiply by 1.5 and use that result? Thanks for any advice, well other than a different and better measuring method, i'm just looking for help on the bias probe as i like measuring without pulling the chassis. Thanks for any advice!!