Voltages in Magnatone 280 vibrato circuit

[dinkotom]

I's a homebrew amp, sounds good, but I expected somewhat stronger vibrato. Checked the voltages, some are off - instead of 58V on the grids of V7 (12BH7) I measured 24V. On pin 2 of the V6 tube - instead of minus 2V I get minus 0.6V and instead of 3V on pin 8 I have about 1V, that's way off specs. I Tried different cathode (820 and 470 Ohms) and plate (470K, 100K) resistor values on V6 and the voltages changed somewhat but still off specs and no change to vibrato depth. Swapped tubes - no change.
Any thoughts how to get closer to specified voltages aprreciated.
Thanks,
Dinko