Alpha 9500 sub 180 second warmup
The specified warmup time for the 8877 tube is 180 seconds. This is a very conservative time, that covers all possible operating conditions, such as heater voltage being at the extreme low end of the specified range. Tests at RFC have shown that tubes routinely reach full emission much sooner than this, especially if the amplifier has only been off for a short period of time. To take advantage of this, the emissions-based warmup timer has been implemented. This timer is disabled by default, so that the full 180 seconds is required. If there is no rush, it is recommended that the amplifier be left to warm up this way. If there is a need to get it on the air more quickly, then enable the emissions checking, and the amplifier will be on the air much quicker. We check for tube emissions, and when we find the tube has warmed up sufficiently, we add 30 seconds after emission is detected, assuring good margin in this process.
The fast(er) warm-up countdown sequence can be enabled by pushing the RCL button, followed by the DIM button and the amplifier will sample the plate current and once tube emissions are detected will switch to 30 seconds remaining .