Sunn Model T 6550 plate resistor?

[donegone]

Im hoping someone here can answer this question. The Model T has a 51 ohm 5 watt plate resistor. I tested it at full power into a dummy load in order to obtain some info for this inquiry. At full power using a 440hz sine, the 6550 output tubes were conducting roughly 180mA each. Using ohms law and the know values we get roughly a 9.18 voltage drop across the 51 ohm plate resistor. Using the power equation we are then able to obtain the resistor power consumption which roughly equals 1.65 watts. My question to the world is what is the purpose of this resistor? I was wondering if it was due to it having an ultra linear output design.

[philbo]

My guess would be that they are there to allow for slight imbalances between the output tubes. It is pretty common to put a small resistance in series with each active component in a power amp circuit to allow putting them in parallel. If there isn't one, the tube with the most gain (or lower plate resistance) does the most work.

[Enzo]

That would be my assumption: ballast rsistors to assure current sharing.

[loudthud]

Have you priced one of those output transformers? The only source I know of is Mercury Magnetic$. When I find these things as fixer uppers there is always atleast one of those resistors blown open, but the transformer is still good