Meng 6PI Biasing Question

[zedrider]

Hello

I am about to replace the 4 power valves on this amplfier (6AQ5 type)
I see there are pre-sets under the valve bases, am i correct in thinking these are for setting the bias on the output valves?

If i am correct how do I go about doing this, I have a Fluke digital multi meter

Gary

[Merlinb]

If it's the one I'm thinking of, those trimmers are hum balance pots. Just twiddle them for the minimum hum, by ear.

[Ian444]

Often the Meng 6P1 has 4 trimpots, 2 for hum balance and 2 for phase splitter balance. The output valves are 6P1 (9 pin) and not 6AQ5 (7 pin) but they are generally considered equivalents. The output valves are self-biased so just fit the new ones, no adjustments should be needed. The Mengs I have seen have the 4 trimpots near the front two input stage valves, not the output valves, so if you have trimpots under the bases of the output valves then disregard this info.