Already broken in tubes stray about 5 mV after 3 weeks or so. I use a somewhat arbitrary number (275 mV) based on an absolute upper limit of 300 mV for the RM-10. After break-in it's more something to do then anything to be concerned about. When new, however, I have had them stray from 275 to over 300 and under 225 after just a few hours. Always wait at least 20 minutes after turn-on so the tubes are warm when you measure.BTW, this applies only to the output EL-84, the inputs, 12ax7 are self-biasing.I imagine the changes are somewhat a function of the design so you need to consult your manufacturer.
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- 11 posts total
- 11 posts total