I have a 74 VT22 (v4) and a 72 V4B. I just bought a bias probe from Eurotubes because I wanted to make sure the fixed bias current was in spec before putting in some NOS Sylvania 7027's in. I ran home at lunch, and hooked it up to both amps. I set the meter to 200ma DCA as instructed, and here's the results: VT22 - 23.5 V4B - 29.8 I know very little about this stuff and since they're basically the same amp, I assumed they both would read around the same. What do these numbers mean? Is one out of spec? They both fluctuated at first, with the VT22 heading down and stabilizing in the mid 23 range. The V4B went down, then climbed back up to the 29's. Experts, help me out!