All, I have an earlier MC240 that has 2 octal sockets. One, as Roscoe pointed out, is for 600Ohm/70V out, but the one next to it is clearly labeled as "stereo preamp power". Looking at the schematic, it shows the octal plug carrying L & R signal and grounds, and 435 VDC. The remaining 3 pins carry 25.2 VAC from a separate center-tapped winding on the power tranny, which leads me to gather that the intended pre-amp has 12.6V filaments stacked in series. So I'll show my ignorance again: Is the limit on the power tranny a cumulative thermal one, or are the 6.3V filament windings of a gauge such that they could not carry any more current? In other words, the main filament winding was intended to power only the tubes on the main chassis, but the tranny, as a unit, was sized to also carry the filament load of the pre-amp as well. Can I run higher-filament-current output tubes since the 25.2V windings are unused, or do I risk burning out the windings? I've seen both opinions on the boards, but I don't trust the technical pedigree of those people as much as I do this group. V/R James
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