And that the100r resistors on pin 7 were intended for OT protection because they were pushing the EL84s hard with nearly 400v B+. I heard a theory that goes back to the very early AC15 that had 350-0-350 PTs. And the AC30/4 has the 100R resistors on pins 9 as well. Also note the AC15 has 100R resistors between pins 9 and the B+ of the EL84 while the AC10 has them between pin 7 and the OT. I am skeptical that these alone could cause a 5w difference. Voltages between the two models being measured differently. If the above picture is a factory original AC10 factory PT then 300v may come down to the originals being above rated spec. Markings are likely under the bell cover. However Vox’s contractors did also use Radio Spares transformers on some amp so, I just don’t know. I don’t entirely disagree about the Radio Spares transformer. But all things similar between the AC10 and the AC15 schematic, voltages post rectifier doesn’t jive between them. Were all the tubes in? And the AC10 schematic may be correct. That will lower supply voltage someone the AC10 if the same transformers are used in both. But do notice the AC10 adds a 200Ω resistor between rectifier and 1st filter cap, which the AC15 does not have. I can't say what is or isn't inside those. I do not own a vintage AC15, and haven't had access to one to measure myself. I'd consider all that "very close agreement" to the AC10 schematic. There was 300v at the OT primary ends, and 296v at the EL84 plates (on the other side of the 100Ω resistors). 310v at the 2nd filter cap (that the AC10 schematic calls "305v source"). 334vdc at the rectifier output (rather than 320vdc) Almost exactly 300-0-300v at the PT high voltage secondary. That said, I measured my own ~1965 AC10 Twin and got: I would suggest we consider what evidence shows the Radiospares transformer is a "factory part"? Because if the factory (and Jennings contracted multiple companies to actually build their amps, maybe 3 or 4?) didn't use it originally, then its exact characteristics are not relevant to the wider "AC15" or "AC10" class of amps.
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