Absolutely. Your question also relates back to your previous issue of voltage measurements at the preamp tubes being too high. In a nutshell, it is impossible to get correct voltage readings almost anywhere in either of these two amplifiers with the output tubes removed -- not only for the reason that Selmerdave indicated, but for even greater reasons with these amplifiers.
Since the output tubes draw over 90% of the total current drawn by the amplifier, it is a foregone conclusion then that with them removed, the overall voltages will be higher as previously stated (basically, no current draw). But in the X-101C and X-101D (and other Fisher amplifiers), the heaters of the four 12AX7 tubes comprising the phono preamp and line stage functions are powered by current draw passing through the output stages. Therefore, if the output tubes are removed, then the heaters of these four 12AX7 tubes will not light at all -- meaning that it is impossible for any of these four tubes to draw any current at all.
With these amplifiers then, not only will the overall voltages be higher with output tubes removed beause of their lack of current draw, but voltages on the earlier stage will also be very high, since their heaters are not even lit up in that scenario. With the output tubes removed, the only tubes that can draw any current in that scenario in either of these amplifiers is the driver tubes, since their heaters are powered by the heater winding in the power transformer.
As to your latest question then, the reason for the extended warmup time is because with the application of power, the output tubes must first start conducting current -- which takes time -- after which only then will the phono preamp and line stage tubes start receiving power to light their heaters. Their warmup time then adds to the warmup time for the output tubes (time events adding in series in this case) -- which itself is further extended because the heaters of these tubes (all connected in series) only operate on about 10 volts each on average (instead of their as connected rating of 12.6 volts), which extends the warmup time for these tubes significantly beyond that when receiving full rated heater voltage.
For these amplifiers -- which use SS power supplies -- at least the warm up time is only about 25 seconds as you measured. For some of Fisher's earlier integrated amplifiers that used a slow warming GZ34 rectifier tube, first it had to warm up, then the output tubes would start conducting, and only then would the preamp and line stage tubes start to warm up. The warm up time for the original X-101 that used this configuration (but only for the phono preamp tubes) was more typically about 40-45 seconds when the phono inputs were selected. I grew up with this amplifier in our house. Having patience during warmup was the order of the day if wanting to listen to a record.
The idea of operating the heaters of the early preamp tubes from current draw passing through the output stages is an economical way to power those heaters from a DC power source, which is but one of the reasons that Fisher amplifiers in general are very quiet designs, having very little inherent hum or noise versus those designs that use AC voltage to power the heaters of their early stages.
I hope this helps!
Dave
