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I finally found time to install two 9.1V, 5W zener diodes in the B+ line (at the standby switch), and that successfully reduced my B+ voltage from its original 390V to 362. My EL84 pin 7 (plate) voltages are now a safer 345 and 347V (down from 370V). This enables me to run NOS EL84s without fear of prematurely burning them out. The amp seems to sound a bit richer as well.

Many thanks to Zaphod and Coco especially for helpful guidance in this regard. On to some playing!

Jim

Boy, that was high. Typical TC-15 is around 350 with our PT. Is your mains high too?

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Stephen
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My mains voltage is 123V. Seems high to me, but these days most USA voltage is close to that, I've read. My voltages from the Trinity PT are 310V (at pins 4 and 6 of the rectifier), which is about 20V higher than what the TC-15 schematic shows as typical. Maybe Heyboer wound me a hot one!

I haven't tried a NOS 5AR4 (don't have one yet) to see if it will reduce the B+ voltage a bit further. I'm running a JJ now. But my present 345/347V at the power tube plates should be ok as is.

Yes, that's pretty good. And don't forget that for the true anode voltage you need to subtract the cathode voltage, which will take it down to somewhere around 333-335V.

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Great tones come in small glass jars!