Too much juice into Yaqin MC-100B, or just bad luck?

[CZ4A]

I recently bought a used Yaqin MC-100B that came with all the stock tubes. I've rolled the 6SN7s and 12AX7s with vintage tubes I have stashed away. Unfortunately, the filament died on one of my rolled 12AX7s (a Telefunken smooth-plate, no less. Grrr...). After the T-Funk half-died I put the stock tubes back in place.

The input voltage I'm seeing to the Yaqin is about 119V. Is that too much for the amp? Time to put this thing on a Variac? Or was it just time for that one triode to shuffle off its mortal coil? I'd really like to not lose another pricey vintage tube...

EDIT: Never mind. I pulled out my trusty multi-meter and heater voltages in the 12AX7 and KT88 sockets are spot-on at 6.3V.

 

[primosounds]

Maybe. But if you are feeling paranoid measure the plate and cathode voltages of the tube in the socket and see how they compare to the schematic.

 

[bimasta]

Time to put this thing on a Variac?

I put my Cary 2A3 on a Variac, for a different purpose — I wanted to spare it from the "shock" of the On-Off switch hitting it with full voltage every time — rather, I was going to "fade" the power up and down, hoping to prolong tube and component lifespans.

It totally killed the amp's musical performance. Frequency extremes disappeared into a bland midrange, and dynamics lost all their punch. The Variac was acting as a "choke" — it wasn't just an ancillary device like a simple power cable, it was like I was was adding an extra transformer into the power supply. I had the same experience using Audio Research amps in a 220V country via step-up transformers — the amps' outputs were severely restricted.