Nos amperex/Philips tube lights up
I did find 4 matched Nos philips/amperex holland made fom 1963 - 1969 here in sweden to a really good price so i brought them and just put them in.
But when i start the pre amp (C500T) the tubes flashes like a normal light bulb for 1 sec and then turn green. is this normal? It did not do this with the gold lions. Everyting else is normal |
Your tubes are fine. Older 12AX7 variants made by Phillips or under license from them exhibit this effect - a bright filament on startup and then dimming down to normal as the tube warms up.
Newer 12AX7A tubes have a more controlled startup and don’t exhibit this behavior. The A suffix stands for controlled filament warmup. Tom |
Ok thank you!
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